Mechanism of the Visible Light-Mediated Gold ... - ACS Publications

Subscriber access provided by CMU Libraries - http://library.cmich.edu

Article

Mechanism of the Visible Light-Mediated GoldCatalyzed Oxyarylation Reaction of Alkenes Qi Zhang, Zhen-Qi Zhang, Yao Fu, and Haizhu Yu ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.5b01971 • Publication Date (Web): 21 Dec 2015 Downloaded from http://pubs.acs.org on December 27, 2015

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Catalysis is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

Mechanism of the Visible Light-Mediated Gold-Catalyzed Oxyarylation Reaction of Alkenes

Qi Zhang,a,b Zhen-Qi Zhang,a Yao Fu,a Hai-Zhu Yu*b

a

Department of Chemistry, University of Science and Technology of China, Hefei 230026 b

Department of Chemistry and Centre for Atomic Engineering of Advanced Materials, Anhui University, Hefei 230601

Emails: [email protected]

1 / 41

ACS Paragon Plus Environment

ACS Catalysis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 41

Abstract A systematic theoretical study has been carried out on the visible light mediated gold-catalyzed oxyarylation of alkenes. The detailed mechanism of the dual Au and photoredox catalyzed difunctionalization, including both the photoredox and gold catalytic cycles has been investigated. The calculation results show that the oxidative quenching of the photoredox catalyst is more favorable than reductive quenching. The favorable gold catalytic cycle is radical addition - SET - coordination cyclization-reductive elimination. The facility of the favorable mechanism is determined by two factors: First, both oxidation steps (i.e. radical addition and SET) occur prior to the cyclization step to generate the feasible cyclization precursor of Au(III) complex. Second, the radical addition formally increases the electron density on the gold center, and thus favors the radical addition-SET sequence.

Keywords:

DFT;

difunctionalization; gold;

photoredox; cyclization

2 / 41


Page 3 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

1. Introduction Transition metal-catalyzed difunctionalization of C-C multiple bond is a powerful synthetic method to elevate the molecular functional complexity, and shows great potential in total synthesis of natural products and pharmaceutical molecules.1-3 In the past decades, various transition metal complexes (such as Pd,4 Cu,5 Fe6, Ag7 and Au8-10) have been used to catalyze the difunctionalization. In this context, gold complexes

have

recently

been

widely

explored

to

accomplish

the

difunctionalizations8-11 such as oxy-/amino-arylation,10a-g,11b oxy-/amino-halogenation, 9c-d,10h-k,

aminooxygenation,10l oxyalkynylation,10m and oxyalkylation11c-e. For example,

after the pioneering studies of Hashmi group,9a-b Toste,10a,10e,10f Zhang,10c,10n Russell,10d,10g and Nevado10l et al. successfully achieved the Au catalyzed oxidative coupling for a series of tosylamide (-NHTs), hydroxyl (-OH), carboxylate (-COOR) and aniline (-NHPh) substituted alkenes and alkynes.10

In these reactions,

PhI(OAc)2 or Selectfluor reagents have been used as the oxidant (Scheme 1a).10 Alternatively, the Pd-Au dual-metal catalytic system eliminates the necessity of strong oxidant, and achieves the difunctionalization of carboxylated allene and alkyne (Scheme 1a).11 Nonetheless, the requirement of stoichiometric gold catalyst or homo-coupling via Pd(0)/Au(I) redox reaction11f limits the application of this strategy. Significantly, Glorius and co-workers12 recently reported a visible light13,14 mediated oxy- and aminoarylation of alkenes at room temperature with catalytic amount of photocatalyst [Ru(bpy)3](PF6)2 and gold catalyst [PPh3Au]NTf2 (Scheme 1b),12a which differs significantly from the more recent visible light induced photoredox 3 / 41


ACS Catalysis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 41

catalysis reactions that rely on dinuclear gold complexes only.15 The dual Au and photoredox catalytic system yields various arylated heterocyclic compounds under mild condition. What is more important, the generation of the aryl radical via the photoredox catalyst avoids the necessity for additional oxidant/stoichiometric gold catalyst and the formation of the homo-coupling products.

Scheme 1.

(a) Au catalyzed oxidative coupling, Au-Pd dual-metal coupling and (b) Au-photoredox catalyzed difunctionalization

In studying the mechanism of the reaction in Scheme 1b, Glorius et al. conducted deuterium labeling experiments (with deuterated alkene) and control experiments (in absence of visible light, photocatalyst or gold catalyst), and suggested a possible mechanism (Scheme 2).12a This mechanism consists of five main steps: coordination (A + 1 → B), cyclization (B→C), radical addition (C+Ph·→D, the phenyl radical is 4 / 41


Page 5 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

generated from photoredox cycle), single electron transfer (SET for short: D + [RuIII] → E + [RuII]), and reductive elimination with the simultaneous catalyst regeneration (E→3+A). Despite this mechanism provides fundamental information into the dual-metal catalyzed difunctionalization in Scheme 1b, many details remain obscure. For example, in a similar Au-photoredox(Ru) catalyzed ring expansion-oxidative arylation reaction, Toste and co-workers suggested that the reaction might begin with the radical addition (i.e. ligation of Ph·, generated from the oxidative quenching of the [RuII]* species), SET and coordination (of the alkene group) steps.16 Inspired by Toste’s proposal, we suggest that the radical addition and SET steps might also occur prior to the cyclization step in Glorius’ reaction system (i.e. A→F→G→H→E in Scheme 2). Similarly, the sequence of the radical addition and the SET steps, and whether the cyclization step occurs on Au(I), Au(II) or Au(III) species are all unanswered questions. Meanwhile, the possibility of the reductive quenching of the photoredox catalyst remains to be examined.13 The answer to these questions will benefit the deep understandings on how the Au(I) catalyst is stepwise oxidized to Au(II) and Au(III), as well as the key factors in determining the efficiency of the cyclization.

5 / 41


ACS Catalysis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 41

Scheme 2. The possible mechanisms of the Au-photoredox catalyzed difunctionalization of 1 To settle the aforementioned problems, we conducted density functional theory (DFT) calculations on Glorius’ reaction system. First, the oxidative quenching of the photoredox is found to be more plausible than the reductive quenching mechanism, due to the lack of strong reductants in the concerned reaction system. Meanwhile, 11 possible pathways regarding the different sequences of the elementary steps (i.e. coordination, radical addition, SET, cyclization and reductive elimination) have been examined. It is found that the cyclization on the Au(I) complex is very energy demanding, and thus the possibility of the Cyclization-Oxidation mechanism (cyclization step occurs before the oxidation steps) can be excluded. By constrast, the high eletrophilicity of the Au(III) center (compared to Au(I) and Au(II)) significantly facilitates the cyclization step, and thus the double oxidation steps (i.e. radical addition and SET) are pre-requisite. In this context, the ligation of Ph· to Au(I) 6 / 41


Page 7 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

transfers partial electron to the Au center, and contributes to the relative facility of the radical addition-SET sequence (relative to the SET-radical addition sequence). With these

disciplines,

the

radical

addition-SET-coordination-cyclization-reductive

elimination is concluded as the most feasible mechanism.

2. Computational methods and model reaction 2.1 Computational methods All the calculations were conducted with the Gaussian09 suite of program.17 The B3LYP18-20/GEN1(GEN1: LanL2dz21 for Au and Ru, and 6-31G(d) for the other atoms) method with SMD22,23 model was used for unrestricted geometry optimization on all structures in methanol solvent (consistent with Glorius’ experiments12a). In addition, the spin-unrestricted broken-symmetry (with the Guess=mix keyword) was used. The frequency analysis (at the same level with optimization) was then conducted to get the thermodynamic corrections of Gibbs free energy and verify the stationary points to be minima or saddle points. For every transition state, intrinsic reaction coordinate (IRC) analysis was performed to confirm that it connects the correct reactant and product on the potential energy surface.24 For complexes that may have different conformations, various structures were calculated and the lowest energy conformation was used in the following discussions. The M0625/GEN2 (GEN2: SDD for Au and Ru, and 6-311++G(d,p) for the other atoms) method with the SMD model was used for the solution phase single-point energy calculations of all these stationary points (with methanol solvent). The polarization function was added for Au 7 / 41


ACS Catalysis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 41

(ζ(f) = 1.050) and Ru (ζ(f) = 1.235).26 All energetics in this study were calculated by adding the Gibbs free energy correction calculated with B3LYP method and the single-point energy calculated with M06 method.27 2.2 Model reaction In accordance with Glorius’ experiments, [Ph3PAu]NTf2 and RuII(bpy)32+ catalyzed difunctionalization of 1a with benzenediazonium 2a in MeOH solvent was chosen as the model reaction (eq 1).12a

3. Results and Discussions To simplify the discussions, we first examined the energetics of different possible pathways with the oxidative quenching mechanism of the photoredox catalyst (Sections 3.1 and 3.2), while the results and discussions on the reductive quenching possibilities are given in Section 3.3.

3.1 Cyclization-Oxidation mechanism

8 / 41


Page 9 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

Figure 1. The energy profiles of Cyclization-Oxidation mechanism (Path 1)

Effort was first put in examining the energy demands of the mechanism proposed by

Glorius

and

co-workers.12a This

mechanism

(Path

1)

is

named

as

Cyclization-Oxidation mechanism10a,10d,28 because cyclization step occurs before the double oxidation (i.e. radical addition and SET) steps. As shown in Figure 1, we start with the original form of the gold catalyst [PPh3Au]NTf2 Int1. Before the catalytic transformation, Int1 could possibly dissociate anion NTf2- to form the cationic Ph3PAu+ (Int2). The process is endergonic by 12.5 kcal/mol. Besides, Int1 could react with the solvent MeOH to give Int3 by ligand exchange. The process is endergonic by 7.5 kcal/mol. Therefore, the Gibbs free energy of Int1 is the lowest among these three intermediates, and it was chosen as the energy reference. Int1 then reacts with the alkene substrate 1a through ligand exchange to generate the Au(I) complex Int4 and free anion NTf2- with free energy decrease of 1.7 kcal/mol. From Int4, cyclization occurs via the concerted transition state TS1, in which the anion (NTf2-) assisted deprotonation and nucleophilic attack of hydroxyl group to the double bond occur 9 / 41


ACS Catalysis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 41

simultaneously (NTf2- is the most possible proton acceptor according to the investigation of various bases in the reaction system). 29 The optimized structure of TS1 in Figure 2 indicates that the Au-C1 bond shortens to 2.104 Å (from 2.297 Å in Int4), and the C1-C2 bond stretches from 1.372 Å to 1.507 Å. The free energy barrier of the cyclization step is 28.5 kcal/mol (Int4→TS1). In comparison, in Toste’s recent theoretical study30 of gold catalyzed alkene amination, the barrier for cyclization is about 10 kcal/mol with NMe3 as an auxiliary base. The high energy barrier of TS1 may be caused by both the weaker nucleophilicity of hydroxyl group (relative to amide group) and the weaker basicity of NTf2- (compared with NMe3). After the cyclization step, the dissociation of HNTf from Int5 then occurs to generate Int6. Subsequently, phenyl radical attacks the Au(I) center of Int6 to generate the Au(II) intermediate Int7. Herein, the phenyl radical is generated from the photoredox cycle. In details, in the oxidative quenching photoredox cycle, the photoredox catalyst RuII(bpy)32+ is first excited to RuII(bpy)32+* under the visible light. Then RuII(bpy)32+* is oxidatively quenched by PhN2+ to generate Ph·, N2 and RuIII(bpy)33+.31 The transformation of Int6 to Int7 is slightly exergonic by 0.7 kcal/mol.32 In Int7, the Au-C(Ph) bond length is 2.276 Å (significantly longer than that of the Au-C1 bond, Figure 2), and the spin density calculation indicates that the single electron mainly locates on the benzene group (The spin densities of the C6H5 moiety are 0.509 and 0.330 of the Ph radical and Int7, respectively). The calculation results imply the weak coordination of Ph· on Au(I) in Int7. Thereafter, Int7 isomerizes to Int8 in which PPh3 and Ph group are in trans position. 33 The isomerization is exergonic by 6.2 10 / 41


Page 11 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

kcal/mol. Then, oxidation of Int8 by [RuIII] ((i.e. RuIII(bpy)33+, which is generated at the same time with phenyl radical as mentioned above.) delivers the Au(III) intermediate Int9 and regenerates the photoredox catalyst [RuII]. According to Marcus theory,34 the activation barrier of this SET step is 3.6 kcal/mol. Finally, Int9 undergoes rapid reductive elimination via TS2 (with an energy barrier of 2.8 kcal/mol) to give the oxyarylation product 3a. The simultaneously generated cationic catalyst Ph3PAu+ further coordinates NTf2- to regenerate the original catalyst Int1. (Note that NTf2- can be regenerated by reaction of HNTf2 with BF4- in MeOH solvent, see Supporting Information).

O C1 C2

Au-C1 = 2.104 C1-C2 = 1.507 C2-O = 1.518

Au-C1 = 2.297 Au-C2 = 2.454 C1-C2 = 1.372 O C2

Au

C1

Au

Int4

Au-C(Ph) = 2.276 Au-C1 = 2.132 C1 C(Ph) Au

TS1

Au-C(Ph) = 2.043 Au-C1 = 2.115 C1

C(Ph)

Au P

Int7

Int9

Figure 2. Optimized structures for selected species. Bond lengths are given in Å.

From Figure 1, the relative Gibbs free energies of TS1, Int5 and Int6 are quite close, and the slightly lower energy of TS1 might be attributed to the fact that the values are given for the Gibbs energy surface, whereas optimization geometries are 11 / 41


ACS Catalysis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 41

done in potential energy surface. Similar observations have also been noted in some other recent theoretical studies.35 For clarity reasons, we use the highest lying species Int6 for the discussions on the overall energy demand of the Cyclization-Oxidation mechanism (Path 1, constituted by coordination - cyclization - radical addition - SET reductive elimination steps). In this context, the overall energy demand is 31.8 kcal/mol (Int4→Int6).

3.2 Oxidation-Cyclization mechanism In this section, we focus on the mechanistic possibilities that one or two oxidative steps (i.e. radical addtion and SET) occur before the cyclizaton step, and these mechanisms are named as the Oxidation-Cyclization10b,c,e,h,36 mechanisms. In these mechanisms, except for the final reductive elimination step and the prior coordination before the cyclization step, the sequences of all other steps are uncertain. For the clarity of discussions, the pathways with the first radical addition, coordination or SET steps are named as Radical-addition-first mechanisms (Path 2, Scheme 3a), Alkene-coordination-first mechanisms (Path 3, Scheme 3b) and SET-first mechanisms (Path 4, Scheme 3c), respectively. The detailed energy profiles of these mechanisms are given Section 3.2.1-3.2.3.

12 / 41


Page 13 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

Path 2A

(a)

Radical addition

cyclization

coordination

SET Path 2B

SET

cyclization

Reductive elimination

coordination Path 2C

cyclization

SET

(b) Path 3A Radical addition Path 3B

cyclization

SET

cyclization

SET Reductive elimination


Radical addition

cyclization

SET Path 3D

cyclization

Radical addition

coordination

cyclization

(c) Path 4A

SET

Radical addition Path 4B

Radical addition


cyclization

cyclization

Reductive elimination

Radical addition

Scheme 3. Oxidation-Cyclization mechanisms ((a) Radical-addition-first mechanisms, (b) Alkene-coordination-first mechanisms, (c) SET-first mechanisms)

3.2.1 Radical-addition-first mechanisms (Path 2) As shown in Figure 3, the addition of Ph· on Int1 in generating the Au(II) intermediate Int10 is exergonic by 2.5 kcal/mol. From Int10, either SET (Path 2A) or coordination step (Paths 2B&2C) might occur, and both the SET-cyclization (Path 2B) and cyclization-SET (Path 2C) sequences are possible on the alkene coordinated intermediate in the latter case (Scheme 3a). All these mechanisms converge at the precursor of the reductive elimination step.

13 / 41


ACS Catalysis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 41

Figure 3. The energy profiles of Radical-addition-first mechanisms

In Path 2A, the formation of the Au(III) intermediate Int11 via the SET of Int10 with [RuIII] is exergonic by 9.8 kcal/mol. The activation barrier of the SET reaction is about 0.1 kcal/mol.34 Subsequently, Int11 coordinates with the alkene substrate 1a to generate Int12 with an energy decrease of 3.3 kcal/mol. Thereafter, NTf2- dissociates from Int12 to generate the intermediate Int13, which then undergoes nucleophilic attack transition state TS3 to generate cyclized intermediate Int14. The O-C2 bond distances of Int13, TS3 and Int14 are 2.834, 2.027 and 1.601 Å respectively, indicating the gradual O-C2 bond formation (Figure 4). The energy barrier of this elementary step is 7.5 kcal/mol (Int13→TS3). Thereafter, the deprotonation of the intermediate Int14 is facilitated by NTf2-, and generates intermediate Int9 and HNTf2 via the transition state TS4. In Int9, the O-C2 bond is further shortened to 1.456 Å. Interestingly, the stepwise cyclization on Int13 (with nucleophilic attack and deprotonation steps) is different from the concerted cyclization step on Au(I) intermediate Int4. The difference might be caused by the different eletrophilicity of 14 / 41


Page 15 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

the Au(I) and Au(III) center. The nucleophlic attack on the double bond with less electrophilic Au(I) is very energy-demanding, and thus the mediation of NTf2- is necessary to increase the nucleophility of the hydroxyl group. By contrast, the nucleophlic attack on the highly electrophilic Au(III) ligated double bond is quite facile, and thus the protonated intermediate Int14 could be located independently. Finally, the facile reductive elimination on Int9 occurs to yield the product 3a and regenerate the catalyst Int1.

Figure 4. Optimized structures for selected species. Bond lengths are given in Å.

In Path 2B, the ligand exchange between Int10 and the alkene substrate 1a occurs to generate the T-shaped intermediate Int15 (see Figure S1 for the optimized structure), and this step is slightly endergonic by 0.9 kcal/mol. Subsequently, the SET step occurs between Int15 and the [RuIII] complex to give the alkene coordinated Au(III) intermediate Int13. This step is exergonic by 8.2 kcal/mol, and the activation barriers is 0.3 kcal/mol. From Int13, the latter transformations in Path 2B are the same as those in Path 2A. Path 2C becomes different from Path 2B on the transformations of the Au(II) 15 / 41


ACS Catalysis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 41

intermediate Int15. In Path 2C, the concerted deprotonation and nucleophilic attack process on Au(II) center occurs via the transition state TS5,37 and this step is endergonic by 24.9 kcal/mol (Int15→Int16).38 The high energy demand indicates the difficulty of the cyclization step on Au(II) center (similar to the results on Au(I) center). Int16 then dissociates HNTf2 to generate Int8, which undergoes SET step with [RuIII] complex to give the Au(III) complex Int9 with an activation barrier of 3.6 kcal/mol. From Int9, the reductive elimination step in Path 2C is the same as those in Path 2A and 2B. Comparing the energy profiles of Path 2A, 2B and 2C in Figure 3, we found that Path 2A is the most favorable mechanism, and the overall energy barrier is 16.5 kcal/mol (Int12→TS2).

3.2.2 Alkene-coordination-first mechanisms (Path 3) Path 3 starts with the coordination of the alkene substrate 1a to the Au(I) center of the catalyst Int1. As shown in Figure 5, the ligand exchange between Int1 and the alkene substrate 1a occurs to generate the alkene coordinated intermediate Int4 with a free energy decrease of 1.7 kcal/mol. From Int4, four possible mechanisms might occur to yield the product 3a (Paths 3A-D). Between the first coordination and the final reductive elimination steps, Path 3A, Path 3B, Path 3C and Path 3D undergo Radical addition - SET - Cyclization, Radical addition - Cyclization - SET, SET Radical addition - Cyclization and SET - Cyclization - Radical addition steps, respectively (Scheme 3b). The detailed energy profiles of Paths 3A-3D are given in 16 / 41


Page 17 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

Figure 5. O -

OH

2+

H

NTf2

Ph3P 32.0

Path 3C

Ph3P 26.7

NTf 2

[Ru ]

-NTf

Int1

-1.1

Int4 OH

Int15

Ph

+ OH

AuI Ph3P

Int13

-1.4

-1.7

AuII Ph3P

+

Ph3P

-9.6

[RuIII]

[RuII]

OH

AuIII Ph3P

[RuII] NTf2 -2.1

NTf 2

NTf2

TS3

Int8

OH

NTf2

+

H

+

O

O AuIII Ph AuIII

III

Au AuIII NTf 2

0.9

3a Int1

+

Ph Ph3P

TS2

-4.1

2+

H O

Int9 -1.9

TS4

-15.6

2+

Int12

Ph

Int16

Ph

[RuIII]

AuII

Ph 2

+ Int8

AuII

Ph3P

Ph

Ph

20.8 Int18

[RuIII] 1a

OH

AuII

Ph3P

26.8

23.2

Int16

O

O

PPh3

33.6

23.5

II

Int19

HNTf2

35.2

TS5

HNTf2

AuII

TS6

Ph

21.6

Path 3D

0.0

Au

II

Int17 -

+

O

PPh3

AuI Path 3B

+ 2

AuII

O

Path 3A

-NTf

H

Ph

Ph3P

Ph

PPh3

Ph3P

Ph

Figure 5. The energy profiles of Alkene-coordination-first mechanisms

As shown in Figure 5, the radical addition of Ph· to Int4 in Path 3A and 3B generates the Au(II) intermediate Int15, and this step is endergonic by 0.3 kcal/mol. In Path 3A, Int15 is then oxidized by [RuIII] complex to generate the Au(III) intermediate Int13. This step is exergonic by 8.2 kcal/mol, and the corresponding activation barrier is 0.3 kcal/mol. The shorter Au-C1 bond of the Au(III) intermediate Int13 (2.343 Å) relative to that of the Au(II) complex Int15 (2.366 Å, Figure S1) implies the stronger Au-alkene interactions in the former case. Furthermore, the spin density calculations indcate that the electron density of the Ph· significantly transfers to the Au center (0.509, 0.256 and 0.000 of Ph group in Ph·, Int15 and Int13, respectively). Thereafter, Int13 undergoes rapid cyclization and reductive elimination steps to yield product 3a. In Path 3B, Au(II)-cyclization occurs on Int15 via the 17 / 41


ACS Catalysis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 41

concerted transition state TS5 to finally yield the cyclized intermediate Int8. Similar to the calculation results in Section 3.2.1, the cyclization on Au(II) intermediate Int15 is very energy-demanding (the free energy barrier is 24.9 kcal/mol, Int15→Int16). In this context, Path 3A involving the cyclization step on Au(III) center is more favorable than Path 3B. In Path 3C and 3D, the alkene coordinated intermediate Int4 then undergoes the SET step to generate the Au(II) intermediate Int17. Note that the removel of one d electron from full-filled 5d orbital39 requires high energy barrier of 33.7 kcal/mol (similar observation has also been noted for the SET of other Au(I) species, vide supra). Int17 then coordinates NTf2- to generate Int18, and this step is exergonic by 5.9 kcal/mol. Next, Int18 undergoes radical addition in Path 3C to generate the Au(III) intermediate Int12 with energy decrease of 36.4 kcal/mol. Int12 then easily dissociates the NTf2- to form Int13, from which the latter transformations in Path 3C are the same as those in Path 3A. In Path 3D, Int18 undergoes Au(II)-cyclization process via the transition state TS6 with free energy of 35.2 kcal/mol. The formed intermediate Int19 then undergoes radical addition to generate Au(III) intermediate Int9, which rapidly goes through the reductive elimination step to yield the product. Similar to the aforementioned conclusions, Path 3C with the cyclization on Au(III) species is more favorable than the Au(II)-cyclization mechanism Path 3D. Comparing the energy profiles of Path 3A and 3C, it is found that radical addition-SET sequence from the coordinated intermediate Int4 in Path 3A is significantly more feasible than the SET-radical addition sequence in Path 3C. In 18 / 41


Page 19 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

other words, Path 3A is the most favorable alkene-coordination-first mechanism, and the overall energy barrier is 16.5 kcal/mol (Int12→TS2). 3.2.3

SET-first mechanisms (Path 4) -

O

+

OH

H

+

NTf2

+

O

AuII

AuII Ph3P Au

II

NTf 2

+ Au Ph3P

II

PPh3

NTf 2

TS6

Int20 25.2

28.4

1a

PPh3

Path 4B

Int19

Path 4C

35.2

Int18

Path 4A

33.6

HNTf 2

20.8 [RuII]

0.0

[RuIII] Int13 -9.6

Int1 Ph3P AuNTf 2

Ph

OH

2+

-15.6 Int12

AuIII Ph3P

-2.1 TS3

+

H O

0.9

3a Int1

-4.1 TS4

NTf2 OH

HNTf 2

NTf2

TS2

Int9 -1.9

NTf 2

2+

+

H

O

+

O

Ph

AuIII Ph3P

AuIII NTf 2 Ph

AuIII

AuIII

Ph

Ph3P

Ph

Ph

PPh3

Ph3P

Figure 6. The energy profiles of SET-first mechanisms

Similar to Sections 3.2.1 and 3.2.2, the different possible mechanisms for the SET-first mechanisms have been examined (Paths 4A-4C in Figure 6). However, as mentioned in Section 3.2.2, the SET of the Au(I) intermediate is very energy demanding due to the difficulty in removel of one d electron from the full filled 5d orbital (Int1 + [RuIII] → Int20 + [RuII] is endergonic by 25.2 kcal/mol, and the activation barrier is 28.4 kcal/mol. Figure 6). Thereafter, all the subequent transformations in Path 4A (with radical addition, coordination, cyclization, reductive elimination steps) are quite facile. By constrast, the coordination-radical addition sequence in Path 4B is energetically less favored than Path 4A, and the cyclization on 19 / 41


ACS Catalysis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 41

the Au(II) complex Int18 in Path 4C results in the high energy demanding transition state TS6. In other words, Path 4A represents the most feasible SET-first mechanism, and its overall energy demand is 28.4 kcal/mol.

3.3 Reductive quenching mechanism

Scheme 4. Reductive quenching mechanism

In addition to the oxidative quenching mechanism, the photoredox catalyst might also transform with reductive quenching catalytic cycle. Currently, no evidence has been provided to exclude such possibility. In this mechanism (Scheme 4), the photoredox catalyst RuII(bpy)32+ is first excited to RuII(bpy)32+* under the visible light. Then RuII(bpy)32+* is reductively quenched by the reductant to generate RuI(bpy)3+. The generated RuI(bpy)3+ reacts with benzenediazonium giving phenyl radical to participate in the radical addition step. In the reaction system, the Au(I) complexes could possibly act as the reductant. Therefore, we examined the SET reactions of the three Au(I) complexes with the excited [RuII]*. Thermodynamically, these transformations are endergonic by 39.1 (Int1→Int20), 42.3 (Int4→Int17) and 20 / 41


Page 21 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

17.3 (Int6→Int19) kcal/mol, respectively. Therefore, the reductive quenching of RuII(bpy)32+* with either Int1 or Int4 is unlikely at room temperature. Meanwhile, despite the energy necessity for SET between Int6 and RuII(bpy)32+* is lower, the generation of Int6 is quite difficult (requires the free energy of 31.8 kcal/mol, Section 3.1). Accordingly, reductive quenching mechanism is unfavorable in the reaction system.

3.4 The favorable mechanism

Figure 7. The energy profiles of Path 2A and Path 3A According to the calculation results in Sections 3.1-3.3, the catalytic cycle of the photoredox catalyst occurs favorably via the oxidative quenching mechanism. In this context, eleven possible pathways have been examined (Paths 1-4). For the Cyclization-Oxidation mechanism (Path 1), the difficulty in cyclization on the Au(I) complex results in high energy demands of 31.8 kcal/mol. This energy is significantly higher than those of the Oxidation-Cyclization mechanisms (Paths 2-4, in which either one or two oxidation steps occur before the cyclization step). Meanwhile, Path 21 / 41


ACS Catalysis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 41

2A, 3A and 4A correspond to the most feasible Radical-addition-first mechanism (among Paths 2A-C, Figure 4), Alkene-coordination-first mechanism (among Path 3A-D, Figure 5) and SET-first mechanism (among Paths 4A-C, Figure 6), respectively. The overall energy demands for these pathways are 16.5, 16.5 kcal/mol, and 28.4 kcal/mol, respectively. Therefore, the significantly higher energy demand of Path 4A excludes its possibility, while both Paths 2A and 3A seems plausible due to the low energy demands. For clarity reasons, the detailed transformations in these two mechanisms are given in Figure 7. In both of them, the double oxidation steps (radical addition and SET) occurs before the cyclization step. In addition, radical addition favorably occurs prior to the SET step. The main difference between them lies in whether the alkene coordination step occurs before or after the double oxidation steps. In Path 3A, the prior alkene coordination step is exergonic by 1.7 kcal/mol, which is slightly unfavorable than the radical addition step in Path 2A by 0.8 kcal/mol. In addition, the subsequent transformations in Path 2A is thermodynamically more feasible than Path 3A, until these two pathways converge at the Au(III) intermediate Int12. In other words, Path 2A is slightly more favorable than Path 3A. Accordingly, Path 2A is the most favorable mechanism.40 According to the aformentioned results and discussions, some experimental observations in Glorius’ reactions can be well understood. First, deuterium labeling experiments with terminal mono-deuterated alkene proceeded diastereoselectively to give the cyclized product. The diastereoselectivty is attributed to the trans-addition cyclization transition state (such as TS3). This calculation result is in line with 22 / 41


Page 23 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

previously reported Au catalyzed cyclization processes.10c-g Second, experimentally, the reaction shuts down when switching off the light, but recovers when reapplying the light irradiation. In the optimal mechanism (Paths 2A), Ph· radical is generated from photoredox cycle and the SET of Au(II) requires the participation of the excited photoredox catalyst.41 Third, no product was gained in the absence of Au catalyst in Glorius’ study. This phenomenon is expected because the direct attack of phenyl radical to the alkene is kinetically highly disfavored.42

3.5 Mechanistic origin of the favorable Path 2A Table 1. The LUMO energies of the cyclization precursors.

Int4

E(LUMO)/a.u.

∆G≠/kcal mol-1

-0.0568

28.5

Int15

Int13

-0.1322

-0.1417

23.0

7.5

We finally sought to clarify the mechanistic origin of the facility of Path 2A (relative to all other mechanisms). Analyzing the detailed transformations of different pathways, we got some interesting observations. First, the energy barriers of cyclization on different Au intermediates vary a lot. In Path 1, the energy barrier of 23 / 41


ACS Catalysis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 41

the elementary cyclization step on Au(I) complex (Int4) is 28.5 kcal/mol (Table 1). In Path 2C and 3B, the energy barrier of cyclization on Au(II) complex (Int15) is 23.0 kcal/mol. By constrast, In Path 2A and 3A, the energy barrier on the Au(III) center is as low as 7.5 kcal/mol (Int13→TS3). The above data indicate that easiness of cyclization might directly relate to the eletrophilicity of Au center. In all cases, the ligation of Au to alkene reduces LUMO orbital energy43 of the alkene group, while the higher eletrophilic Au(III) center results in the lower LUMO energy (Table 1). Accordingly, the nucleophilic attack of the oxygen atom to the terminal C2 atom could be significantly facilitated by nucleophilic Au species. In this context, the cyclization of Au(III) reuqires the prior occurance of the double oxidation steps.

Scheme 5. Comparison between Path 2A and Path 4

E(eV)

Int1

Int20

HOMO

electron

-0.26 SOMO

electron

HOMO-1

-0.27

HOMO

HOMO

HOMO-1

HOMO-1

HOMO-3

HOMO-2

HOMO-2

HOMO-4

HOMO-3

HOMO-3

HOMO-2

-0.28

-0.29

24 / 41


Page 25 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

Figure 8. Frontier molecular orbital of Int1 and Int20

Second, in Path 2A, the radical addition step tends to occur before the SET step. As shown in Scheme 5, the radical addition with the subsequent SET steps on Int1 are exergonic by 2.5 and 9.8 kcal/mol, respectively. However, in Path 4, the direct SET step on Int1 is highly endergonic by 25.2 kcal/mol with activation barrier of 28.4 kcal/mol. As mentioned above, the difficulty in removel one d electron from the full 5d orbital results in the high energy demands of the SET on Au(I). In the frontier orbitals of the Au(I) center of Int1, all the 5d orbitals are occupied (Figure 8). After the SET step in Path 4, one electron on dx2-y2 orbital is taken by the [RuIII] catalyst, and thus the stable 5d10 electron configuration changes to the instable 5d9 odd-electron configuration.39 By constrast, in Path 2A (Scheme 5), the radical addition on Int1 partially transfers the single electron from Ph· to the Au center. The spin density of the C6H5 moiety reduces from 0.509 of the Ph radical to 0.111 in the Au(II) intermediate Int10. As a result, the Au-C(Ph) bond is shortened to 2.047 Å, indicating the strong Au-Ph interactions therein. The strong interaction results in the energy decrease of 2.5 kcal/mol. In the subsequent SET step, the Au(II) intermediate Int10 gives one electron to the [RuIII] complex delivering even-electron configuration Au(III) center and [RuII] complex (unlike the reaction between Au(I) center and [RuIII] complex giving odd-electron Au(II) center). This step results in the stronger Au-C(Ph) and Au-P bonds (the Au-P and Au-C(Ph) bond length reduces from 2.597 and 2.047 Å to 2.398 and 2.037 Å, respectively). Similar observation has also been noted for the 25 / 41


ACS Catalysis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 41

SET of other Au(II) species. In other words, the partial electron transfer from Ph· to Au(I) results in the preferable radical addition-SET sequence than the SET-radical addition sequence.

4. Conclusion Gold catalyzed difunctionalization is a powerful synthetic method to elevate molecular complexity. Recently, Glorius et al. accomplished the visible light mediated oxy- and aminoarylation of alkenes with the dual Au and photoredox catalyst at room temperature. Despite of the great synthetic potential, the mechanism remains obscure in many details (such as the sequence of cyclization and oxidation, the order of two oxidation steps and the mechanism of photoredox cycle). Through systematic theoretical calculations, we found that: for the photoredox cycle, oxidative quenching mechanism is more favorable than reductive quenching. For the gold catalytic cycle, radical addition - SET - coordination - cyclization - reductive elimination is the favorable mechanism. In the mechanism, the cyclization step occurs on the highly electron-deficient Au(III) center, so as to avoid the difficult cyclization steps on the Au(I) or Au(II) centers. Meanwhile, the radical addition step tends to occur before the SET step, because the SET on Au(I) is energetically highly disfavored. In other words, the facility of the favorable mechanisms is two-fold: First, the ligation of the highly electrophilic Au(III) reduces the LUMO energy and facilitates the cyclization. Second, phenyl attack of Au(I) transfers partial single electron to the Au center to generate strong Au-Ph interactions, which prompts favorable radical addition-SET sequence. 26 / 41


Page 27 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

Supporting Information. Optimized structure of Int 15, complete content for Ref 29, 31, 32, 33, 34, 37, 40, 41 and 42, regeneration of NTf2- and Cartesian coordinates, free energies, and thermal corrections. This material is available free of charge via the Internet at http://pubs.acs.org. Corresponding Author [email protected] (Hai-Zhu Yu) Notes The authors declare no competing financial interest. Acknowledgement We thank the NSFC Program

(21202006, 21325208, 21172209, 21361140372), the 973

(2012CB215306),

FRFCU

(WK2060190025,

WK2060190040,

FRF-TP-14-015A2), CAS (KJCX2-EW-J02), PCSIRT and National Supercomputing Center in Shenzhen and USTC for providing the computational resources.

Reference：： (1)

Reviews of difunctionalization: (a) Merino, E.; Nevado, C. Chem. Soc. Rev. 2014, 43, 6598-6608. (b) Beccalli, E. M.; Broggini, G.; Gazzola, S.; Mazza, A. Org. Biomol. Chem. 2014, 12, 6767-6789. (c) Romero, R. M.; Wöste, T. H.; Muñiz, K. Chem.-Asian J. 2014, 9, 972-983. (d) Muñiz, K.; Hövelmann, C. H.; Streuff. J. J. Am. Chem. Soc. 2008, 130, 763-773. (e) McDonald, R. I.; Liu, G.; 27 / 41


ACS Catalysis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 41

Stahl, S. S. Chem. Rev. 2011, 111, 2981-3019. (f) Chemler, S. R. Org. Biomol. Chem. 2009, 7, 3009-3019. (g) MuÇiz, K. Angew. Chem., Int. Ed. 2009, 48, 9412-9423. (h) Jensen, K. H.; Sigman, M. S. Org. Biomol. Chem. 2008, 6, 4083-4088. (i) Kotov, V.; Scarborough, C. C.; Stahl, S. S. Inorg. Chem. 2007, 46, 1910-1923. (j) Li, G.; Kotti, S. R. S. S.; Timmons, C. Eur. J. Org. Chem. 2007, 2745-2758. (2)

Yan, M.; Lei, M.; Hosseini, A. S.; Chemler, S. R. J. Am. Chem. Soc. 2012, 134, 12149-12156.

(3)

Pathak, T. P.; Gligorich, K. M.; Welm, B. E.; Sigman, M. S. J. Am. Chem. Soc. 2010, 132, 7870-7871.

(4)

(a) Zhu, R.; Buchwald, S. L. Angew. Chem., Int. Ed. 2012, 51, 1926-1929. (b) Huang, L.; Wang, Q.; Liu, X.; Jiang, H. Angew. Chem., Int. Ed. 2012, 51, 5696-5700. (c) Wu, T.; Mu, X.; Liu, G. Angew. Chem., Int. Ed. 2011, 50, 12578-12581. (d) Mu, X.; Wu, T.; Wang, H.; Guo, Y.; Liu, G. J. Am. Chem. Soc. 2012, 134, 878-881. (e) Martínez, C.; Muňiz, K. Angew. Chem., Int. Ed. 2012, 51, 7031-7034. (f) Qiu, S.; Xu, T.; Zhou, J.; Guo, Y.; Liu, G. J. Am. Chem. Soc. 2010, 132, 2856-2857. (g) Jensen, K. H.; Webb, J. D.; Sigman, M. S. J. Am. Chem. Soc. 2010, 132, 17471-17482. (h) Wu, T.; Yin, G.; Liu, G. J. Am. Chem. Soc. 2009, 131, 16354-16355. (i) Wang, A.; Jiang, H.; Chen, H. J. Am. Chem. Soc. 2009, 131, 3846-3847. (j) Jensen, K. H.; Pathak, T. P.; Zhang, Y; Sigman, M. S. J. Am. Chem. Soc. 2009, 131, 17074-17075. (k) Li, Y.; Song, D.; Dong, V. M. J. Am. Chem. Soc. 2008, 130, 2962-2964. (l) Muňiz, K.; Hövelmann, C. H.; Streuff, J. J. 28 / 41


Page 29 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

Am. Chem. Soc. 2008, 130, 763-773. (m) Muňiz, K. J. Am. Chem. Soc. 2007, 129, 14542-14543. (n) Desai, L. V.; Sanford, M. S. Angew. Chem., Int. Ed. 2007, 46, 5737-5740. (o) Zhang, Y.; Sigman, M. S. J. Am. Chem. Soc. 2007, 129, 3076-3077. (5)

(a) Egami, H.; Shimizu, R.; Kawamura, S.; Sodeoka, M. Angew. Chem., Int. Ed. 2013, 52, 4000-4003. (b) Zhang, H.; Pu, W.; Xiong, T.; Li, Yan.; Zhou, X.; Sun, K.; Liu, Q.; Zhang, Q. Angew. Chem., Int. Ed. 2013, 52, 2529-2533. (c) Matsuda, N.; Hirano, K.; Satoh, T.; Miura, M. J. Am. Chem. Soc. 2013, 135, 4934-4937. (d) Bovino, M. T.; Chemler, S. R. Angew. Chem., Int. Ed. 2012, 51, 3923-3927. (e) Wang, Y.; Zhu, X.; Chiba, S. J. Am. Chem. Soc. 2012, 134, 3679-3682. (f) Zhu, R.; Buchwald, S. L. J. Am. Chem. Soc. 2012, 134, 12462-12465. (g) Liwosz, T. W.; Chemler, S. R. J. Am. Chem. Soc. 2012, 134, 2020-2023. (h) Zhao, B. G.; Peng, X. G.; Zhu, Y.; Ramirez, T. A.; Cornwall, R. G.; Shi, Y. J. Am. Chem. Soc. 2011, 133, 20890-20900. (i) Sequeira, F. C.; Turnpenny, B. W.; Chemler, S. R. Angew. Chem., Int. Ed. 2010, 49, 6365-6368. (j) Huang, L.; Jiang, H.; Qi, C.; Liu, X. J. Am. Chem. Soc. 2010, 132, 17652-17654. (k) Zhao, B. G.; Peng, X. G.; Cui, S. L.; Shi, Y. A. J. Am. Chem. Soc. 2010, 132, 11009-11011. (l) Fuller, P. H.; Kim, J. W.; Chemler, S. R. J. Am. Chem. Soc. 2008, 130, 17638-17639. (m) Michaelis, D. J.; Shaffer, C. J.; Yoon, T. P. J. Am. Chem. Soc. 2007, 129, 1866-1867. (n) Zeng, W.; Chemler, S. R. J. Am. Chem. Soc. 2007, 129, 12948-12949.

(6)

(a) Wei, W.; Zhou, M.; Fan, J.; Liu, W.; Song, R.; Liu, Y.; Hu, M.; Xie, P.; Li, J. Angew. Chem., Int. Ed. 2013, 52, 3638-3641. (b) Liu, G. S.; Zhang, Y. Q.; Yuan, 29 / 41


ACS Catalysis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 41

Y. A.; Xu, H. J. Am. Chem. Soc. 2013, 135, 3343-3346. (c) Williamson, K. S.; Yoon, T. P. J. Am. Chem. Soc. 2012, 134, 12370-12373. (d) Liu, W.; Li, Y.; Liu, K.; Li, Z. J. Am. Chem. Soc. 2011, 133, 10756-10759. (e) Williamson, K. S.; Yoon, T. P. J. Am. Chem. Soc. 2010, 132, 4570-4571. (7)

Ag catalyzed difunctionalization: (a) Li, Z.; Song, L.; Li, C. J. Am. Chem. Soc. 2013, 135, 4640-4643. (b) Li, Y. M.; Sun, M.; Wang, H. L.; Tian, Q. P.; Yang, S. D. Angew. Chem., Int. Ed. 2013, 52, 3972-3976.

(8)

For recent reviews, please see: (a) Hashmi, A. S. K.; Hutchings, G. J. Angew. Chem., Int. Ed. 2006, 45, 7896. (b) Liu, L. P.; Hammond, G. B. Chem. Soc. Rev. 2012, 41, 3129-3139. (c) Rudolph, M.; Hashmi, A. S. K. Chem. Soc. Rev. 2012, 41, 2448-2462. (d) Wegner, H. A.; Auzias, M. Angew. Chem., Int. Ed. 2011, 50, 8236-8247. (e) Hopkinson, M. N.; Gee, A. D.; Gouverneur, V. Chem.-Eur. J. 2011, 17, 8248-8262. (f) Garcia, P.; Malacria, M.; Aubert, C.; Gandon, V.; Fensterbank, L. ChemCatChem 2010, 2, 493-497.

(9)

(a) Hashmi, A. S. K.; Ramamurthi, T. D.; Rominger, F. J. Organomet. Chem. 2009, 694, 592-597. (b) Hashmi, A. S. K.; Blanco, M. C.; Fischer, D.; Bats, J. W. Eur. J. Org. Chem. 2006, 1387-1389. (c) Wang, T.; Shi, S.; Rudolph, M.; Hashmi, A. S. K. Adv. Synth. Catal. 2014, 356, 2337-2342. (d) Wang, T.; Huang, L.; Shi, S.; Shi, S. Chem. Eur. J. 2014, 20, 14868-14871.

(10) (a) Brenzovich, W. E.; Benitez, D.; Lackner, A. D.; Shunatona, H. P.; Tkatchouk, E.; Goddard, W. A., III; Toste, F. D. Angew. Chem., Int. Ed. 2010, 49, 5519-5522. (b) Zhu, S.; Ye, L.; Wu, W.; Jiang, H. Tetrahedron 2013, 69, 10375-10383. (c) 30 / 41


Page 31 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

Zhang, G.; Cui, L.; Wang, Y.; Zhang, L. J. Am. Chem. Soc. 2010, 132, 1474-1475. (d) Ball, L. T.; Lloyd-Jones, G. C.; Russell, C. A. Chem.-Eur. J. 2012, 18, 2931-2937. (e) Melhado, A. D.; Brenzovich, W. E.; Lackner, A. D., Jr.; Toste, F. D. J. Am. Chem. Soc. 2010, 132, 8885-8887. (f) Brenzovich, W. E., Jr.; Brazeau, J.-F.; Toste, F. D. Org. Lett. 2010, 12, 4728-4731. (g) Ball, L. T.; Green, M.; Lloyd-Jones, G. C.; Russell, C. A. Org. Lett. 2010, 12, 4724-4727. (h) Arcadi, A.; Pietropaolo, E.; Alvino, A.; Michelet, V. Beilstein. J. Org. Chem. 2014, 10, 449-458. (i) Li, S.; Li, Z.; Yuan, Y.; Li, Y.; Zhang, L.; Wu, Y. Chem.-Eur. J. 2013, 19, 1496-1501. (j) Arcadi, A.; Pietropaolo, E.; Alvino, A.; Michelet, V. Org. Lett., 2013, 15, 2766-2769. (k) Schuler, M.; Silva, F.; Bobbio, C.; Tessier, A.; Gouverneur, V. Angew. Chem., Int. Ed. 2008, 47, 7927-7930. (l) Haro, T.; Nevado, C. Angew. Chem., Int. Ed. 2011, 50, 906-910. (m) Song, D.-H.; Ryu, J.-S. Bull. Korean Chem. Soc. 2014, 35, 2635-2644. (n) Zhang, G.; Luo, Y.; Wang, Y.; Zhang, L. Angew. Chem., Int. Ed. 2011, 50, 4450-4454. (11) (a) Hirner, J. J.; Shi, Y.; Blum, S. A. Acc. Chem. Res. 2011, 44, 603-613. (b) Hashmi, A. S. K.; Lothschütz, C.; Döpp, R.; Rudolph, M.; Ramamurthi, T. D.; Rominger, F. Angew. Chem., Int. Ed. 2009, 48, 8243-8246. (c) Shi, Y.; Ramgren, S. D.; Blum, S. A. Organometallics 2009, 28, 1275-1277. (d) Al-Amin, M.;

Johnson, J. S.; Blum, S. A. Organometallics 2014, 33, 5448-5456. (e) Shi, Y.; Roth, K. E.; Ramgren, S. D.; Blum, S. A. J. Am. Chem. Soc. 2009, 131, 18022-18023. (f) Weber, D.; Gagné, M. R. Chem. Commun. 2011, 47, 5172-5174. 31 / 41


ACS Catalysis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 41

(12) (a) Sahoo, B.; Hopkinson, M. N.; Glorius, F. J. Am. Chem. Soc. 2013, 135, 5505-5508. (b) Sahoo, B.; Li, J. L.; Glorius, F. Angew. Chem., Int. Ed. 2015, 54, 11577-11580. (c) Hopkinson, M. N.; Sahoo, B.; Li, J. L.; Glorius, F. Chem. -Eur. J. 2014, 20, 3874-3886. (d) Hopkinson, M. N.; Sahoo, B.; Glorius, F. Adv. Synth. Catal. 2014, 356, 2794-2800. (13) For recent reviews: (a) Zeitler, K. Angew. Chem., Int. Ed. 2009, 48, 9785-9789. (b) Yoon, T. P.; Ischay, M. A.; Du, J. Nat. Chem. 2010, 2, 527-532. (c) Narayanam, J. M. R.; Stephenson, C. R. J. Chem. Soc. Rev. 2011, 40, 102-113. (d) Xuan, J.; Xiao,W.-J. Angew. Chem., Int. Ed. 2012, 51, 6828-6838. (e) Ravelli, D.; Fagnoni, M. ChemCatChem 2012, 4, 169-171. (f) Hari, D. P.; Kçnig, B. Angew. Chem., Int. Ed. 2013, 52, 4734-4743. (g) Fukuzumi, S.; Ohkubo, K. Chem. Sci. 2013, 4, 561-574. (h) Xi, Y.; Yi, H.; Lei, A. Org. Biomol. Chem. 2013, 11, 2387-2403. (i) Prier, C. K.; Rankic, D. A.; MacMillan, D. W. C. Chem. Rev. 2013, 113, 5322-5363. (14) (a) Nicewicz, D. A.; MacMillan, D. W. C. Science 2008, 322, 77-80. (b) Nagib, D. A.; Scott, M. E.; MacMillan, D. W. C. J. Am. Chem. Soc. 2009, 131, 10875-10877. (c) Shih, H.-W.; Vander Wal, M. N.; Grange, R. L.; MacMillan, D. W. C. J. Am. Chem. Soc. 2010, 132, 13600-13603. (d) Pirnot, M. T.; Rankic, D. A.; Martin, D. B. C.; MacMillan, D. W. C. Science 2013, 339, 1593-1596. (e) Petronijević, F. R.; Nappi, M.; MacMillan, D. W. C. J. Am. Chem. Soc. 2013, 135, 18323-18326. (f) Tarantino, K. T.; Liu, P.; Knowles, R. R. J. Am. Chem. Soc. 2013, 135, 10022-10025. (g) Rono, L. J.; Yayla, H. G.; Wang, D. Y.; Armstrong, 32 / 41


Page 33 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

M. F.; Knowles, R. R. J. Am. Chem. Soc. 2013, 135, 17735-17738. (h) Kalyani, D.; McMurtrey, K. B.; Neufeldt, S. R.; Sanford, M. S. J. Am. Chem. Soc. 2011, 133, 18566-18569. (i) Ye, Y.; Sanford, M. S. J. Am. Chem. Soc. 2012, 134, 9034-9037. (j) Liu, Q.; Yi, H.; Liu, J.; Yang, Y.; Zhang, X.; Zeng, Z.; Lei, A. Chem.-Eur. J. 2013, 19, 5120-5126. (15) (a) Revol, G.; McCallum, T.; Morin, M.; Gagosz, F.; Barriault, L. Angew. Chem., Int. Ed. 2013, 52, 13342-13345. (b) Xie, J.; Shi, S.; Zhang, T.; Mehrkens, N.; Rudolph, M.; Hashmi, A. S. K. Angew. Chem., Int. Ed. 2015, 54, 6046-6050. (16) Shu, X.; Zhang, M.; He, Y.; Frei, H.; Toste, F. D. J. Am. Chem. Soc. 2014, 136, 5844-5847. (17) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A. Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Keith, T.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; 33 / 41


ACS Catalysis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 34 of 41

Daniels, A. D.; Farkas, O.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J.; Gaussian 09, revision D.01; Gaussian, Inc.: Wallingford CT, 2013. (18) Becke, A. D. J. Chem. Phys. 1993, 98, 5648-5652. (19) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785-789. (20) B3LYP have been frequently used in previous theoretical study. For Au system, see: (a) Geng, C.; Zhu, R.; Li, M.; Lu, T.; Wheeler, S. E.; Liu, C. Chem.-Eur. J. 2014, 20, 15833-15839. (b) Wang, Z. J.; Benitez, D.; Tkatchouk, E.; Goddard, W. A., III; Toste, F. D. J. Am. Chem. Soc. 2010, 132, 13064-13071. (c) Li, R.; Kobayashi, H.; Tong, J.; Yan, X.; Tang, Y.; Zou, S.; Jin, J.; Yi, W.; Fan, J. J. Am. Chem. Soc. 2012, 134, 18286-18294. (d) Ariafard, A.; Asadollah, E.; Ostadebrahim, M.; Rajabi, N. A.; Yates, B. F. J. Am. Chem. Soc. 2012, 134, 16882-16890. (e) Zhukhovitskiy, A. V.; Mavros, M. G.; Voorhis, T. V.; Johnson, J. A. J. Am. Chem. Soc. 2013, 135, 7418-7421. (f) Garayalde, D.; Gómez-Bengoa, E.; Huang, X.; Goeke, A.; Nevado, C. J. Am. Chem. Soc. 2010, 132, 4720-4730. (g) Marion, N.; Carlqvist, P.; Gealageas, R.; Frémont, P.; Maseras, F.; Nolan, S. P. Chem.-Eur. J. 2007, 13, 6437-6451. (h) Nakanishi, W.; Yamanaka, M.; Nakamura, E. J. Am. Chem. Soc. 2005, 127, 1446-1453. (i) Nieto-Oberhuber, C.; Pérez-Galán, P.; Herrero-Gómez, E.; Lauterbach, T.; Rodríguez, C.; López, S.; Bour, C.; Rosellón, A.; Cárdenas, D. J.; Echavarren, A. M. J. Am. Chem. Soc. 2008, 130, 269-279. (j) Faza, O. N.; López, C. S.; Álvarez, R.; Lera, A. R. J. Am. Chem. Soc. 2006, 128, 2434-2437. (k) Comas-Vives, A.; Ujaque, G. J. Am. Chem. Soc. 2013, 135, 1295-1305. (l) Xia, Y.; Dudnik, A. S.; Gevorgyan, V.; Li, Y. J. Am. Chem. Soc. 2008, 130, 6940-6941. (m) Dudnik, A. S.; Xia, Y.; Li, Y.; 34 / 41


Page 35 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

Gevorgyan, V. J. Am. Chem. Soc. 2010, 132, 7645-7655. For Ru system, see: (n) Fantacci, S.; Angelis, F. D.; Wang, J.; Bernhard, S.; Selloni, A. J. Am. Chem. Soc. 2004, 126, 9715-9723. (o) Fung, W. K.; Huang, X.; Man, M. L.; Ng, S. M.; Hung, M. Y.; Lin, Z.; Lau, C. P. J. Am. Chem. Soc. 2003, 125, 11539-11544. (p) Salassa, L.; Garino, C.; Salassa, G.; Gobetto, R.; Nervi, C. J. Am. Chem. Soc. 2008, 130, 9590-9597. (q) Bowles, F. L.; Olmstead, M. M.; Balch, A. L. J. Am. Chem. Soc. 2014, 136, 3338-3341. (r) Kuznetsov, A. E.; Geletii, Y. V.; Hill, C. L.; Morokuma, K.; Musaev, D. G. J. Am. Chem. Soc. 2009, 131, 6844-6854. (s) Arndt, M.; Salih, K. S. M.; Fromm, A.; Goossen, L. J.; Menges, F.; Niedner-Schatteburg, G. J. Am. Chem. Soc. 2011, 133, 7428-7449. (t) Liu, P.; Xu, X.; Dong, X.; Keitz, B. K.; Herbert, M. B.; Grubbs, R. H.; Houk, K. N. J. Am. Chem. Soc. 2012, 134, 1464-1467. (u) Takaoka, A.; Moret, M.-E.; Peters, J. C. J. Am. Chem. Soc. 2012, 134, 6695-6706. For many other transition metal system, see: (v) Yu, H.-Z.; Jiang, Y.-Y.; Fu, Y.; Liu, L. J. Am. Chem. Soc. 2010, 132, 18078-18091. (w) Fu, Y.; Li, Z.; Liang, S.; Guo, Q.-X.; Liu, L. Organometallics 2008, 27, 3736-3742. (x) Zhang, S.-L.; Fu, Y.; Shang, R.; Guo, Q.-X.; Liu, L. J. Am. Chem. Soc. 2010, 132, 638-646. (y) Zhang, Q.; Yu, H.-Z.; Li, Y.-T.; Liu, L.; Huang, Y.; Fu, Y. Dalton Trans. 2013, 42, 4175-4184. (21) Wadt, W. R.; Hay, P. J. J. Chem. Phys. 1985, 82, 299-310. (22) Hollwarth, A.; Bohme, M.; Dapprich, S.; Ehlers, A. W.; Gobbi, A.; Jonas, V.; Kohler, K. F.; Stegmann, R.; Veldkamp, A.; Frenking, G. Chem. Phys. Lett. 1993, 208, 237-240. 35 / 41


ACS Catalysis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 36 of 41

(23) Geometry optimization with SMD model have been frequently used in previous theoretical study, for examples: (a) Lu, G.; Fang, C.; Xu, T.; Dong, G.; Liu, P. J. Am. Chem. Soc. 2015, 137, 8274-8283. (b) Citek, C.; Gary, J. B.; Wasinger, E. C.; Stack, T. D. P. J. Am. Chem. Soc. 2015, 137, 6991-6994. (c) Garrido-Barros, P.; Funes-Ardoiz, I.; Drouet, S.; Benet-Buchholz, J.; Maseras, F.; Llobet, A. J. Am. Chem. Soc. 2015, 137, 6758-6761. (d) Lei, Z.-Q.; Pan, F.; Li, H.; Li, Y.; Zhang, X.-S.; Chen, K.; Wang, X.; Li, Y. -X.; Sun, J.; Shi, Z.-J. J. Am. Chem. Soc. 2015, 137, 5012-5020. (e) Hoveln, R. V.; Hudson, B. M.; Wedler, H. B.; Bates, D. M.; Gros, G. L.; Tantillo, D. J.; Schomaker, J. M. J. Am. Chem. Soc. 2015, 137, 5346-5354. (24) Gonzalez, C.; Schlegel, H. B. J. Phys. Chem. 1990, 94, 5523-5527. (25) Zhao Y.; Truhlar, D. G. Theor. Chem. Acc. 2008, 120, 215-241. (26) Ehlers, A. W.; Bohme, M.; Dapprich, S.; Gobbi, A.; Hollwarth, A.; Jonas, V.; Kohler, K. F.; Stegmman, R.; Veldkamp, A.; Frenking, G. Chem. Phys. Lett. 1993, 208, 111-114. (27) B3LYP//M06 method have been frequently used in transition metal theoretical study, for examples: (a) Lin, M.; Kang, G.-Y.; Guo,Y.-A.; Yu, Z.-X. J. Am. Chem. Soc. 2012, 134, 398-405. (b) Herbert, M. B.; Lan, Y.; Keitz, B. K.; Liu, P.; Endo, K.; Day, M. W.; Houk, K. N.; Grubbs, R. H. J. Am. Chem. Soc. 2012, 134, 7861-7866. (c) Hong, X.; Stevens, M. C.; Liu, P.; Wender, P. A.; Houk, K. N. J. Am. Chem. Soc. 2014, 136, 17273-17283. (d) Zhang, Q.; Yu, H.-Z.; Fu, Y. Organometallics 2013, 32, 4165-4173. (e) Jiang, Y.-Y.; Yu, H.-Z. Fu, Y. 36 / 41


Page 37 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

Organometallics 2013, 32, 926-936. (28) Reference about cyclization occurs before oxidation: Peng, Y.; Cui, L.; Zhang, G.; Zhang, L. J. Am. Chem. Soc. 2009, 131, 5062-5063. (29) In absence of an auxiliary base, this nucleophilic attack process is very difficult. The C-O bond automatically breaks during geometry optimization. Previous works about the role of the counterion: (a) Kovács, G.; Ujaque, G.; Lledós, A. J. Am. Chem. Soc. 2008, 130, 853-864. (b) Xia, Y.; Dudnik, A. S.; Gevorgyan, V.; Li, Y. J. Am. Chem. Soc. 2008, 130, 6940-6941. Besides, other possible proton acceptors have been investigated, please see Supporting Information for more details. (30) Tkatchouk, E.; Mankad, N. P.; Benitez, D.; Goddard, W. A., III; Toste, F. D. J. Am. Chem. Soc. 2011, 133, 14293-14300. (31) The possibility for Au(I) catalyzed oxidization of PhN2+ to phenyl radical is excluded, because the possible transformations are highly endergonic. Please see Supporting Information for more details. (32) The potential energy surface of the process is very gentle. Please see Supporting Information for the PES by gradually shortening the Au-C(Ph) bond length. (33) The energy barrier of the direct SET of Int7 with [RuIII] is 37.1 kcal/mol. Therefore, Int7 first isomerizes to Int8 in which PPh3 and Ph group are in trans position. Then SET occurs on Int8 with lower energy barrier of 26.8 kcal/mol. Please see Supporting Information for more details. (34) Please see Supporting Information for the calculation details. The references 37 / 41


ACS Catalysis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 38 of 41

about Marcus theory: (a) Marcus, R. A. J. Chem. Phys. 1956, 24, 966-978. (b) Marcus, R. A. J. Chem. Phys. 1956, 24, 979-989. (c) Marcus, R. A. J. Chem. Phys. 1957, 26, 872-877. (d) Hush, N. S. J. Chem. Phys. 1958, 28, 962-972. (e) Marcus, R. A. Can. J. Chem. 1959, 37, 155-163. (f) Hush, N. S. Trans. Faraday Soc. 1961, 57, 557-580. (g) Marcus, R. A. Faraday Discuss. Chem. Soc. 1982, 74, 7-15. (h) Marcus, R. A.; Sutin, N. Biochem. Biophys. Acta 1985, 811, 265-322. (i) Houmam, A. Chem. Rev. 2008, 108, 2180-2237. (j) Lin, C. Y.; Coote, M. L.; Gennaro, A.; Matyjaszewski, K. J. Am. Chem. Soc. 2008, 130, 12762-12774. (k) Jones, G. O.; Liu, P.; Houk, K. N.; Buchwald, S. L. J. Am. Chem. Soc. 2010, 132, 6205-6213. (35) (a) Wu, X.-N.; Zhao, Y.-X.; Xue, W.; Wang, Z.-C.; He, S.-G.; Ding, X.-L. Phys. Chem. Chem. Phys. 2010, 12, 3984-3997. (b) Zhao, Y.-X.; Wu, X.-N.; Ma, J.-B.; He, S.-G.; Ding, X.-L. J. Phys. Chem. C 2010, 114, 12271-12279. (c) Ma, J.-B.; Wu, X.-N.; Zhao, Y.-X.; Ding, X.-L.; He, S.-G. Phys. Chem. Chem. Phys. 2010, 12, 12223-12228. (d) Feyel, S.; Döbler, J.; Hoeckendorf, R.; Beyer, M. K.; Sauer, J.; Schwarz, H. Angew. Chem., Int. Ed. 2008, 47, 1946-1950. (36) Reference on oxidation-cyclization mechanisms: (a) Wang, W.; Jasinski, J.; Hammond, G. B.; Xu, B. Angew. Chem., Int. Ed. 2010, 49, 7247-7252. (b) Qian, D.; Zhang, J. Beilstein J. Org. Chem. 2011, 7, 808-812. (c) Simonneau, A.; Garcia, P.; Goddard, J. P.; Mouriès-Mansuy, V.; Malacria, M.; Fensterbank, L. Beilstein J. Org. Chem. 2011, 7, 1379-1386. (37) Au(II) intermediates Int15 could possibly transform to its isomer Int15′ via a 38 / 41


Page 39 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

low energy barrier of 5.5 kcal/mol. Int15 and Int15′ lead to the cyclization transition states TS5′ and TS5, respectively. Despite the low energy transition states TS5 corresponds to the less stable intermediate (Int15′), the precursor can be easily formed by the aforementioned isomerization from Int15. Therefore, Int15→Int15′→TS5 is the favorable mechanism. Nonetheless, for clarity reasons, Int15′ is omitted in the manuscript. Please see Supporting Information for more details. (38) The corresponding structure like Int14 does not exist in Au(I) and Au(II)-cyclization process, because of the lower eletrophilicity of Au(I) and Au(II) centers. (39) (a) Mohamed, A. A.; Abdou, H. E.; Fackler, J. P., Jr. Coord. Chem. Rev. 2010, 254, 1253-1259. (b) Laguna, A.; Laguna, M. Coord. Chem. Rev. 1999, 193-195, 837-856. (40) The solvent effect of MeOH has also been examined for this mechanism. Please see Supporting Information for more details. (41) Toste and co-workers proposed an alternative mechanism in reference 16 that Au(II) complex reacts with aryldiazonium salt to give Au(III) complex and a phenyl radical, without regeneration of the photocatalyst. However, this mechanism is unlikely in our concerned reaction system. Please see Supporting Information for more details. (42) The mechanism that the phenyl radical directly attack the alkene to initiate the cyclization is unfavorable. Please see Supporting Information for more details. 39 / 41


ACS Catalysis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 40 of 41

(43) (a) Hong, X.; Bercovici, D. A.; Yang, Z.; Al-Bataineh, N.; Srinivasan, R.; Dhakal, R. C.; Houk, K. N.; Brewer, M. J. Am. Chem. Soc. 2015, 137, 9100-9107. (b) Törk, L.; Jiménez-Osés, G.; Doubleday, C.; Liu, F.; Houk, K. N. J. Am. Chem. Soc. 2015, 137, 4749-4758. (b) Xie, S.; Lopez, S. A.; Ramström, O.; Yan, M.; Houk, K. N. J. Am. Chem. Soc. 2015, 137, 2958-2966.

40 / 41


Page 41 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Catalysis

Table of Content

41 / 41


Mechanism of the Visible Light-Mediated Gold ... - ACS Publications

Recommend Documents