Electro-Oxidative CâC Alkenylation by Rhodium(III) Catalysis - Journal

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Electrooxidative C–C Alkenylation by Rhodium(III) Catalysis Youai Qiu, Alexej Scheremetjew, and Lutz Ackermann J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.8b13692 • Publication Date (Web): 12 Jan 2019 Downloaded from http://pubs.acs.org on January 12, 2019

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Journal of the American Chemical Society

Electrooxidative C–C Alkenylation by Rhodium(III) Catalysis Youai Qiu,† Alexej Scheremetjew,† and Lutz Ackermann* Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstrasse 2, 37077, Göttingen, Germany. Supporting Information ABSTRACT: Electrochemical C–C activations were accomplished by expedient oxidative rhodium(III) catalysis. Thus, oxidative C–C alkenylations proved viable with the aid of electricity, avoiding the use of toxic and/or expensive transition metal oxidants. The chelation-assisted C–C functionalizations proceeded with ample scope and excellent levels of chemoand position-selectivities within an organometallic C–C activation manifold. Detailed mechanistic studies provided support for a kinetically-relevant C–C scission, and a well-defined organometallic rhodium(III) complex was identified as catalytically competent intermediate. The electrochemical C–C functionalization was devoid of additional electrolytes, could be conducted on gram scale, and provided position-selective access to densely-1,2,3-subtituted arenes, which are not viable by C–H activation.

1.

INTRODUCTION

C–H activation has emerged as a powerful platform for molecular sciences, with transformative applications to inter alia medicinal chemistry, crop protection and material sciences.1 In sharp contrast, methods for the catalytic activation of strong C–C bonds continue to be scarce,2 with great, yet largely untapped potential for molecular assembly and late-stage diversification. In recent years, considerable progress in C–C activation catalysis has been realized by Murakami,3 Bower,4 Dong,5 and Shi,6 among others.7 Despite these major advances, oxidative C–C activations continue to heavily depend upon expensive and/or toxic transition metals as the sacrificial oxidants, prominently featuring copper(II) and silver(I). In the meantime, electrocatalysis has been identified as an increasingly viable approach for preventing stoichiometric redox-reagents in organic synthesis.8 Hence, this approach has recently proven instrumental for establishing alkene functionalizations,9 direct oxygenations,10 reductive and oxidative couplings,11 polymerizations,12 as well as C–H activations13 with palladium,14 cobalt,15 ruthenium,16 rhodium,17 iridium,18 copper,19a and nickel19b complexes. In sharp contrast to this very recent progress in electrochemical C–H activation, organometallic C–C functionalizations by electrocatalysis has thus far proven elusive. Within our program on sustainable C–C activation,20 we have now developed the first electrochemically-enabled, organometallic C–C activation, on which we report herein. Notable features of our strategy include (a) unprecedented electrooxidative C–C activations by versatile rhodium(III) catalysis, (b) chemical oxidant-free C–C alkenylations avoiding stoichiometric copper and silver byproducts, (c) electricity as a user-friendly oxidant,

(d) and mechanistic insights into electrooxidative C–C functionalizations, including detailed cyclovoltammetric analysis. It is furthermore noteworthy that the C–C activation strategy provided unique access to challenging densely-1,2,3-trisubtituted arenes, which cannot be prepared by any C–H functionalization method.

Scheme 1. Electrooxidative C–C functionalization Electrochemical C–C Activation rDG

O R

R

H

1R

rDG

Pt

RVC

R3

H

2

+

1

R3 2

Rh

R

+ 3

O R2

R1

+ H2

4

electrocatalytic C–C activation rhodium catalysis no Cu(II), or Ag(I) mechanistic insights electricity as green oxidant

2.

RESULTS AND DISCUSSION

Optimization Studies We initiated our studies by exploring various reaction conditions for the envisioned electrooxidative C–C functionalization of tertiary benzylic alcohol 1a in a userfriendly undivided cell set-up. Orienting experiments indicated [Cp*RhCl2]2 as a viable catalyst, particularly in combination with a platinum plate cathode and a reticulated vitreous carbon (RVC) anode, along with KOAc as additive in H2O at 100 °C (Scheme 2). To our

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delight, the desired C–C activation product 3aa was obtained in 35% yield. To the best of our knowledge, efficient electrooxidative C–C activation by transition metal catalysis had, as of yet, not been reported. Scheme 2. Preliminary electrochemical C–C activation

observation

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Table 1. Optimization of electrochemical C–C activationa

of

N

N

RVC OH H Me + Me

Ph

N

RVC

OH Me Me

+

Ph

Me 1a

2a

1a

Pt N

[Cp*RhCl2]2 (2.5 mol %) KOAc, H2O 100 °C, 8 h, CCE at 4.0 mA

Pt

catalyst (2.5 mol %)

Me N

rhodium-catalyzed

2a

additives, solvent 100 °C, 8 h CCE at 4.0 mA Me

N

N Ph

3aa

N Ph

Me 3aa: 35%

Based on these exciting initial results, we further interrogated the electrochemical C–C/C–H functionalization regime (Table 1; Table S-1 in the Supporting Information).21 After considerable experimentation, we were pleased to find that the desired transformation was best realized with a solvent mixture of t-AmOH and H2O, and KOAc as the additive in an operationally simple undivided cell (entries 1-5). It is noteworthy that these findings highlight the watertolerant nature of the electrochemical C–C alkenylation, which, moreover, did not require an additional electrolyte. Control experiments confirmed the essential role of the electricity, the carboxylate additive22 and the rhodium-catalyst for the electrooxidative C–C/C–H functionalization (entries 6-15). While iridium catalysis was not a viable option (entry 9), electrooxidative ruthenium-catalyzed C–C activation was observed, albeit with somewhat reduced efficacy under otherwise identical reaction conditions (entry 10).

Entry

catalyst

additive

solvent

3aa (%)b

1

[Cp*RhCl2]2

KOAc

H2O

35

2

[Cp*RhCl2]2

KOAc

t-AmOH

10

3

[Cp*RhCl2]2

KOAc

TFE

18c

4

[Cp*RhCl2]2

KOAc

toluene

–d

5

[Cp*RhCl2]2

KOAc

t-AmOH/H2O (3:1)

82

6

[Cp*RhCl2]2

KOAc

t-AmOH/H2O (3:1)

9e

7

[Cp*RhCl2]2

KOAc

t-AmOH/H2O (1:1)

69

8

[Cp*RhCl2]2

KOAc

t-AmOH/H2O (7:1)

51

9

[Cp*IrCl2]2

KOAc

t-AmOH/H2O (3:1)

–

10

[Ru]

KOAc

t-AmOH/H2O (3:1)

34 f

11

–

KOAc

t-AmOH/H2O (3:1)

–g

12

[Cp*RhCl2]2

K2CO3

t-AmOH/H2O (3:1)

46

13

[Cp*RhCl2]2

NaOPiv

t-AmOH/H2O (3:1)

61

14

[Cp*RhCl2]2

KPF6

t-AmOH/H2O (3:1)

8

15

[Cp*RhCl2]2

–

t-AmOH/H2O (3:1)

22

Undivided cell, RVC anode, Pt cathode, constant current at 4.0 mA, 1a (0.25 mmol), 2a (0.5 mmol), catalyst (2.5 mol %), additive (2.0 equiv), solvent (4.0 mL), 100 °C, under N2, 8 h. b Isolated yield. c 70 °C. d n-Bu4NBF4 (0.1 M) was added. e Without electricity. f [RuCl2(p-cymene)]2 (5.0 mol %) was used. g Without [Rh] catalyst. a

Thereafter, we probed the effect exerted by the substitution pattern of the leaving group in substrates 1 (Scheme 3). Hence, a variety of alcohols was subjected to the optimized reaction conditions of the electrochemical C–C activation. Interestingly, tertiary and secondary alcohols bearing either aryl or alkyl groups smoothly underwent the C–C alkenylation process. Contrarily, a primary alcohol or an ether fell short in delivering the desired products 3, illustrating the importance of the acidic functionality for inducing the C–C cleavage event. It is furthermore noteworthy that an attempted electrooxidative C–H alkenylation gave the product 3aa in a significantly diminished yield of only 16% under otherwise identical reaction conditions, reflecting the complementary potential of electrochemical C–C activation. To our delight, the desired product 3da was obtained in 50% yield with imine as the leaving group.


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Scheme 3. Examination of leaving group substitution pattern

N

N

R

R

RVC

OH 2 + 1R

Ph

1

2a

N

N

R

2

Me

N

N

N

KOAc t-AmOH/H2O (3/1) 100 °C, 6-8 h CCE at 4.0 mA

N

OH

R = H (3da): R = CH3 (3da): R = CF3 (3da): R = F (3da):

R

RVC

DG OH

Ph

+

R

O R2

R1 4

3

R1 = Me, R2 = Me (3aa): 82% R1 = Ph, R2 = H (3aa): 84% R1 = Me, R2 = H (3aa): 46% R1 = H, R2 = H (3aa): ---

OH 1R

Pt

[Cp*RhCl2]2 (2.5 mol %)

Scheme 4. Electrochemical C–C alkenylation of arenes 1

N

R

R

1R

2

+

1

N

72% 69% 35% 48%

N

N

N

Me

N

N

N

Me Ph

O

N

3da: ---

N

Me

N

OH

N

N

N

CF3 3ca: 32%

N

Me

N

Me

N

N Ph

3fa: 65%

N

N Ph

Ph

Ph Me

OH Me

3ha: 75%

N Me

1af: ---

Ph

3ea: 62%

3da: --N

N

Ph

3ga: 58%

N

N

Me

Me

3da: 50%

4

Me N

R2

R1

3

Me 3ba: 71%

3aa: 84%

OMe

O

+

Ph

3da: 72%

N Ph HN

Ph R

N

Ph

3da: ---

N

DG


N

H Me 3aa: 16%

Ph 2a

N

Pt

[Cp*RhCl2]2 (2.5 mol %)

3ia: 78% N

N Ph

MeO

Ph

Ph

1ag: ---

OMe 3ja: 81%

Versatility and Scope With the thus optimized reaction conditions for the electrooxidative C–C activation established, we explored its versatility with a set of representative arenes 1 (Scheme 4). Differently substituted substrates 1 bearing para-, meta-, and ortho-substituents were thereby well accepted. In addition to pyrazolyl arenes 1a-1f, we were delighted to observe that indazolyl and pyridinyl-substituted arenes 1g and 1h-1l likewise underwent the C–C alkenylation with high levels of chemo- and position-selectivity.

3ka: 78%

3la: 68%

Next, we turned our attention to probing the scope of amenable olefins 2 (Scheme 5). Thus, styrenes 2 bearing electron-withdrawing or electron-donating substituents afforded the corresponding products 3 with high catalytic efficacy. Notably, halogen substituents were fully tolerated, which should prove invaluable for orthogonal late-stage diversification. We were also pleased to observe that the sensitive cyano group remained chemoselectively untouched by the electrochemical C–C functionalization manifold. Useful olefinic substrates, such as the acrylate 2p and vinyl phosphonate 2q, were also found to react effectively to afford the corresponding products 3ap and 3aq, respectively.



Scheme 5. Electrooxidative C–C activation using alkenes 2 N

N

RVC

OH Me + Me

R


Me 1a

2

N

N

Pt

N

[Cp*RhCl2]2 (2.5 mol %)

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at a reduced catalyst loading without compromising the catalyst’s efficacy (Scheme 7b).

N R

O

+

Me

Me

Me 3

4a

Scheme 7. Traceless removal and gram scale electrocatalytic C–C activation (a) Removal of Pyrazole Group

R

R = Me (3ab): R = CF3 (3ac): R = t-Bu (3ad): R = OMe (3ae):

71% 76% 73% 58%

R = Ph (3af): R = F (3ag): R = Cl (3ah): R = Br (3ai):

72% 62% 68% 66%

N

Me

N

N

N

CN

N

N

N

N

Me

Me

3aj: 71%

N

Me

Me

N

N

3am: 51%

N

1a: 6 mmol

3ao: 85%

N

N

N

Me

3aq: 66%

3ap: 43%

The unique power of the C–C functionalization approach was clearly highlighted by the position-selective synthesis of 1,2,3-tri-substituted arenes 3ma-3me (Scheme 6). These findings demonstrate the beneficial assets of the C–C activation strategy, while structural motifs of 1,2,3tri-substituted arenes cannot be accessed by C–H activation. Scheme 6. Position-selective rhodium-catalyzed C–C activation

N

N

H

RVC

OH R

1

N

N Ph Me

3ma: 68%

N

N

Me

H

N

H

R

KOAc t-AmOH/H2O (3/1) 100 °C, 8 h CCE at 4.0 mA

2

N

H

Pt

[Cp*RhCl2]2 (2.5 mol %)

Me + Me Me

+

Me 3

N

Pt N

[Cp*RhCl2]2 (1.5 mol %) Ph

2a

KOAc t-AmOH/H2O (3/1) 100 °C, 12 h, 30 mA

N Ph

Me 3aa: 75%, 1.17 g

Mechanistic Studies

O P OEt OEt

CO2n-Bu Me

RVC OH Me Me

Me

3an: 64%

N

N

Me

Br

Me

5a: 75%

3al: 93%

N N

Me

(b) Gram scale transformation

3ak: 62%

N

Ph

3aa

Br

Me

Me

2) aq. HCl, MeOH, 40 °C, 2 h

Me

NH2

1) TMSCl, TMPMgCl LiCl, 0 °C, 38 h

Ph

N

OMe

H Me

Me

3mb: 62%

3me: 55%

The practical utility of the thus established electrooxidative rhodium-catalyzed C–C activation was next substantiated by the traceless removal of the pyrazolyl motif,7a thereby furnishing synthetically meaningful anilines 5 (Scheme 7a). Notably, the electrochemical rhodium-catalyzed C–C transformation could be easily conducted on gram scale (6.0 mmol), even

Given the efficiency of the unprecedented electrocatalytic C–C activation, we became attracted to delineating its modus operandi. To this end, three competition reactions between electronically differentiated substrates 1 and 2 were performed under the optimized conditions, as depicted in Scheme 8a. Here, the more electron-rich arenes 1 were preferentially converted, which can be rationalized by the more nucleophilic nature of an rhodium(III) organometallic intermediate (vide infra). Furthermore, the more electronrich styrene 2 reacted predominantly, which is in line with a kinetically-relevant migratory olefin insertion. An additional competition experiment was conducted to test the relative efficacies of the C–C and the C–H functionalizations. Counterintuitively, we found that the C–C activation occurred significantly faster as compared to the corresponding C–H activation (Scheme 8b). When the C–C alkenylation was conducted in the presence of the isotopically labelled cosolvent D2O, we did not observe a notable deuterium incorporation (Scheme 8c), thus being indicative of a slow C–C scission, accompanied by a fast subsequent migratory insertion of the coordinated alkene. In addition, this observation highlights the preferential C–C over C–H cleavage. Furthermore, gas-chromatographic headspace analysis confirmed the formation of molecular hydrogen as the byproduct (Scheme 8d).21 To probe the organometallic nature of the electrooxidative C–C alkenylation, we independently prepared the well-defined complex 6a and 6b,23 which proved to be a competent catalyst likewise (Scheme 8e).


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Scheme 8. Summary of key mechanistic studies on electrochemical C–C activation (a) competition experiment

N

N

(a) electrochemical oxidation Pt

RVC OH Ph

R = CH3 (1a) R = H (1d)

2a

N

Ph

KOAc t-AmOH/H2O (3/1) 100 °C, 5 h CCE at 4.0 mA 3aa/3da = 2.4/1

R

N

N

[Cp*RhCl2]2 (2.5 mol %)

+

Me Me

Scheme 9. Electrochemical versus chemical C–C alkenylation

N

Ph +

R

RVC

OH Ph

Me

R = CH3 (3aa): 52% R = H (3da): 22%

1ab

Pt

N

[Cp*RhCl2]2 (2.5 mol %)

2a


N Ph

Me

3aa: 84%

(b) chemical oxidation N

N

RVC

OH Me Me

+

Ph

N

N

2a

RVC

OH Me Me

N

Me 1a

2b/2c

N

OH

N

Pt N

1ab

N

H +

R = CH3 (3ab): 32% R = CF3 (3ac): 28%

2a

1a'

N


Me 1ab

Pt

[Cp*RhCl2]2 (2.5 mol %)

Ph

N

R R = CH3 (3aa): 52% R = H (3da): 10%

3aa/3da = 5.2/1

(c) D2O as cosolvent

N

N

H

RVC OH Me Me

+

N

N

H

KOAc t-AmOD/D2O (3/1) 100 °C, 2 h CCE at 4.0 mA

tBu

Me 1b

< 5% D

Pt

[Cp*RhCl2]2 (2.5 mol %)

< 5% D

< 5% D N

OD

N

tBu

H

H

+

Me Me

H Me

Me [D]n-1b: 51%

2d

< 5% D

[D]n-3bd: 22%

(d) headspace H2-analysis

N

N

RVC

OH Ph

+

Ph

Me 1ab

Pt

[Cp*RhCl2]2 (2.5 mol %) KOAc, MeOH 45 °C, 5 h CCE at 4.0 mA

N

N Ph

+

H2 confirmed by headspace GC-analysis

Me

2a

3aa

N

RVC

OH Ph +

1d

Pt

6a or 6b (5.0 mol %) Ph

2a


N

Me Me

N Ph

3da: 67% (6a) 70% (6b)

Ph

2a

oxidant (1.2 equiv), KOAc t-AmOH/H2O (3/1) 100 °C, 8 h, N2

N Ph

Me

Ag2CO3 (3aa): 64% Cu(OAc)2 (3aa): 66%

Finally, we performed detailed mechanistic studies by means of cyclic voltammetry (Figure 1).24 The starting materials 1 and 2 were found to be electrochemically inert within the investigated redox window, whereas product 3aa exhibited a distinct oxidation peak at Ep = 0.93 V versus Fc+/0 (Figure 1a), which is in line with our observation that extended reaction times led to decomposition of the product. Upon addition of KOAc to [Cp*RhCl2]2 the cyclic voltammogram clearly indicated a ligand exchange, forming [Cp*Rh(OAc)2]2 (Figure 1b). The proposed re-oxidation of the rhodium(I) species to regenerate the catalytically competent rhodium(III) intermediate was explored with the well-defined Cp*Rh(I) complex [Cp*Rh(cod)] (Figure 1c). This complex was thus shown to be easily oxidized at Ep = -0.16 V versus Fc+/0. Notably, the process was found to be facilitated by the presence of HOAc, which is being formed during the reductive elimination step. We did not observe any indication for the coordination of the product 3aa after its release via β-H-elimination (Figure 1d).

(e) well-defined complex 6 N

N

[Cp*RhCl2]2 (2.5 mol %)

R

Me

RVC

N

Ph +

OH

Me

R = CH3 (3ba): 48% R = CF3 (3ca): 17%

(b) C–C activation versus C–H activation

N

N

Ph +

KOAc t-AmOH/H2O (3/1) 100 °C, 5 h CCE at 4.0 mA 3ab/3ac = 1.1/1

CH3/CF3

N

R

[Cp*RhCl2]2 (2.5 mol %)

+

N Ph

KOAc t-AmOH/H2O (3/1) 100 °C, 5 h CCE at 4.0 mA 3ba/3ca = 2.8/1

CH3/CF3 1b/1c

Pt

[Cp*RhCl2]2 (2.5 mol %)

Me

Me Me

N Rh Cl N

6a

Me Me

Me

Me Me

N Rh OAc N

6b

Thereafter, we compared the efficacy of the electrochemical C–C activation with the one observed when employing chemical oxidants (Scheme 9). Interestingly, typically used chemical oxidants, such as copper(II) acetate or silver(I) acetate, furnished the desired product 3aa in significantly inferior yields under otherwise identical reaction conditions.



Page 6 of 10

subsequently affords the rhodium(I) intermediate 11 through hydride elimination and reductive elimination. Finally, an anodic oxidation of the rhodium(I) intermediate 11 regenerates the catalytically active rhodium(III) complex. Scheme 10. Proposed catalytic cycle [Cp*RhCl2]2 RVC

N

N

RVC

OH

Pt

2 HOAc

1

[Cp*Rh(OAc)2]2

anodic oxidation

Pt

cathodic reduction

Me Me

HOAc Me N

N

Me

Me Me N Rh N OAc O Me

Cp*RhL2 11

R + HOAc

H2

Me Me

3 electrocatalytic C–C activation no Cu(II), no Ag(I) electricity as green oxidant H2 as sole byproduct

-hydride elimination reductive elimination Me Me N

Me

Me Me

7 C–C activation

O Me

Me Me Me

N Rh OAc R Me Me

10

OAc

Me

N Rh N

9

Me

Me Me

4

N Rh OAc N Me Me R

8 R OAc

2

migratory insertion

3. CONCLUSIONS

Figure 1. Cyclic voltammetry. Conditions: a), b) and d): MeOH, 0.1 M [n-Bu4N][PF6], 1 mM substrates, 100 mV/s; c): MeOH, 0.1 M KOAc, 4 mM [Cp*Rh(cod)], 100 mV/s.

In conclusion, we have reported on the first electrochemical C−C activation by expedient rhodium catalysis. Thus, oxidative C−C alkenylations were achieved by electricity, which avoided the formation of metal-containing stoichiometric byproducts. The versatile rhodium catalysis manifold occurred with excellent levels of chemo- and position-selectivities, generating H2 as the sole byproduct. Mechanistic studies provided support for a slow C−C cleavage within an organometallic regime. Our findings highlight the unique synthetic utility of electrocatalysis for sustainable C−C functionalizations. The power of the C–C activation strategy was likewise substantiated by providing position-selective access to densely-1,2,3-substituted arenes, which cannot be obtained by any of the existing C–H functionalization method.

ASSOCIATED CONTENT

Proposed Catalytic Cycle

Supporting Information

Based on our mechanistic studies, a plausible catalytic cycle for the rhodium-electrocatalyzed C–C alkenylation was proposed, as depicted in Scheme 10. Coordination of substrate 1 through its nitrogen and oxygen to the rhodium(III) catalyst generates intermediate 7, and thereby set the stage for a the key C–C cleavage. Thereafter, migratory alkene insertion occurs to furnish the seven-membered rhoda(III)cycle 10, which

Experimental procedures and compound characterization data, including the 1H/13C NMR spectra. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author *[email protected]


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Author Contributions †These

authors contributed equally.

Notes

The authors declare no competing financial interest.

ACKNOWLEDGMENT Generous support by the DFG (Gottfried-Wilhelm-Leibniz award to LA) is gratefully acknowledged.

REFERENCES (1) (a) Piou, T.; Rovis, T., Electronic and Steric Tuning of a Prototypical Piano Stool Complex: Rh(III) Catalysis for C–H Functionalization. Acc. Chem. Res. 2018, 51, 170-180; (b) Gandeepan, P.; Ackermann, L., Transient Directing Groups for Transformative C–H Activation by Synergistic Metal Catalysis. Chem 2018, 4, 199-222; (c) Shang, R.; Ilies, L.; Nakamura, E., IronCatalyzed C–H Bond Activation. Chem. Rev. 2017, 117, 9086-9139; (d) Park, Y.; Kim, Y.; Chang, S., Transition Metal-Catalyzed C–H Amination: Scope, Mechanism, and Applications. Chem. Rev. 2017, 117, 9247-9301; (e) He, J.; Wasa, M.; Chan, K. S. L.; Shao, Q.; Yu, J.-Q., Palladium-Catalyzed Transformations of Alkyl C–H Bonds. Chem. Rev. 2017, 117, 8754-8786; (f) Neufeldt, S. R.; Sanford, M. S., Controlling Site Selectivity in PalladiumCatalyzed C–H Bond Functionalization. Acc. Chem. Res. 2012, 45, 936-946; (g) Arockiam, P. B.; Bruneau, C.; Dixneuf, P. H., Ruthenium(II)-catalyzed C–H bond activation and functionalization. Chem. Rev. 2012, 112, 5879-5918; (h) Satoh, T.; Miura, M., Oxidative Coupling of Aromatic Substrates with Alkynes and Alkenes under Rhodium Catalysis. Chem. E. J. 2010, 16, 11212-11222; (i) Davies, H. M.; Manning, J. R., Catalytic C–H Functionalization by Metal Carbenoid and Nitrenoid Insertion. Nature 2008, 451, 417-424; (j) Bergman, R. G., C–H Activation. Nature 2007, 446, 391-393. (2) (a) Song, F.; Gou, T.; Wang, B. Q.; Shi, Z. J., Catalytic Activations of Unstrained C–C Bond Involving Organometallic Intermediates. Chem. Soc. Rev. 2018, 47, 7078-7115; (b) Nairoukh, Z.; Cormier, M.; Marek, I., Merging C–H and C–C Bond Cleavage in Organic Synthesis. Nat. Rev. Chem. 2017, 1; (c) Fumagalli, G.; Stanton, S.; Bower, J. F., Recent Methodologies That Exploit C–C Single-Bond Cleavage of Strained Ring Systems by Transition Metal Complexes. Chem. Rev. 2017, 117, 9404-9432; (d) Chen, P. H.; Billett, B. A.; Tsukamoto, T.; Dong, G., "Cut and Sew" Transformations via Transition-Metal-Catalyzed Carbon–Carbon Bond Activation. ACS Catal. 2017, 7, 1340-1360; (e) Murakami, M.; Ishida, N., Potential of Metal-Catalyzed C–C Single Bond Cleavage for Organic Synthesis. J. Am. Chem. Soc. 2016, 138, 13759-13769; (f) Souillart, L.; Cramer, N., Catalytic C–C Bond Activations via Oxidative Addition to Transition Metals. Chem. Rev. 2015, 115, 9410-9464; (g) Marek, I.; Masarwa, A.; Delaye, P. O.; Leibeling, M., Selective Carbon–Carbon Bond Cleavage for the Stereoselective Synthesis of Acyclic Systems. Angew. Chem. Int. Ed. 2015, 54, 414-429; (h) Chen, F.; Wang, T.; Jiao, N., Recent Advances in Transition-Metal-Catalyzed Functionalization of Unstrained Carbon–Carbon Bonds. Chem. Rev. 2014, 114, 86138661; (i) Murakami, M.; Matsuda, T., Metal-Catalysed Cleavage of Carbon–Carbon Bonds. Chem. Commun. 2011, 47, 1100-1105; (j) Jun, C. H., Transition Metal-Catalyzed Carbon–Carbon Bond Activation. Chem. Soc. Rev. 2004, 33, 610-618. (3) (a) Okumura, S.; Sun, F.; Ishida, N.; Murakami, M., Palladium-Catalyzed Intermolecular Exchange between C–C and C–Si sigma-Bonds. J. Am. Chem. Soc. 2017, 139, 12414-12417; (b) Ishida, N.; Necas, D.; Masuda, Y.; Murakami, M., Enantioselective Construction of 3-Hydroxypiperidine Scaffolds by Sequential Action of Light and Rhodium upon N-

Allylglyoxylamides. Angew. Chem. Int. Ed. 2015, 54, 7418-7421; (c) Ishida, N.; Sawano, S.; Murakami, M., Stereospecific Ring Expansion from Orthocyclophanes with Central Chirality to Metacyclophanes with Planar Chirality. Nat. Commun. 2014, 5, 3111; (d) Murakami, M.; Ashida, S.; Matsuda, T., Nickel-Catalyzed Intermolecular Alkyne Insertion into Cyclobutanones. J. Am. Chem. Soc. 2005, 127, 6932-6933; (e) Murakami, M.; Amii, H.; Shigeto, K.; Ito, Y., Breaking of the C–C Bond of Cyclobutanones by Rhodium(I) and Its Extension to Catalytic Synthetic Reactions. J. Am. Chem. Soc. 1996, 118, 8285-8290; (f) Murakami, M.; Amii, H.; Ito, Y., Selective Activation of Carbon-Carbon Bonds Next to a Carbonyl Group. Nature 1994, 370, 540-541. (4) (a) Wang, G. W.; McCreanor, N. G.; Shaw, M. H.; Whittingham, W. G.; Bower, J. F., New Initiation Modes for Directed Carbonylative C–C Bond Activation: RhodiumCatalyzed (3 + 1 + 2) Cycloadditions of Aminomethylcyclopropanes. J. Am. Chem. Soc. 2016, 138, 1350113504; (b) Shaw, M. H.; McCreanor, N. G.; Whittingham, W. G.; Bower, J. F., Reversible C–C Bond Activation Enables Stereocontrol in Rh-Catalyzed Carbonylative Cycloadditions of Aminocyclopropanes. J. Am. Chem. Soc. 2015, 137, 463-468; (c) Shaw, M. H.; Croft, R. A.; Whittingham, W. G.; Bower, J. F., Modular Access to Substituted Azocanes via a RhodiumCatalyzed Cycloaddition-Fragmentation Strategy. J. Am. Chem. Soc. 2015, 137, 8054-8057; (d) Shaw, M. H.; Melikhova, E. Y.; Kloer, D. P.; Whittingham, W. G.; Bower, J. F., Directing Group Enhanced Carbonylative Ring Expansions of Amino-substituted Cyclopropanes: Rhodium-Catalyzed Multicomponent Synthesis of N-Heterobicyclic Enones. J. Am. Chem. Soc. 2013, 135, 49924995. (5) (a) Deng, L.; Jin, L.; Dong, G., Fused-Ring Formation by an Intramolecular "Cut-and-Sew" Reaction between Cyclobutanones and Alkynes. Angew. Chem. Int. Ed. 2018, 57, 2702-2706; (b) Deng, L.; Chen, M.; Dong, G., Concise Synthesis of (-)-Cycloclavine and (-)-5-epi-Cycloclavine via Asymmetric C– C Activation. J. Am. Chem. Soc. 2018, 140, 9652-9658; (c) Xia, Y.; Lu, G.; Liu, P.; Dong, G., Catalytic Activation of Carbon–Carbon Bonds in Cyclopentanones. Nature 2016, 539, 546-550; (d) Zeng, R.; Dong, G., Rh-Catalyzed Decarbonylative Coupling with Alkynes via C–C Activation of Isatins. J. Am. Chem. Soc. 2015, 137, 1408-1411; (e) Ko, H. M.; Dong, G., Cooperative Activation of Cyclobutanones and Olefins leads to Bridged Ring Systems by a Catalytic [4 + 2] Coupling. Nat. Chem. 2014, 6, 739-744; (f) Xu, T.; Dong, G., Rhodium-Catalyzed Regioselective Carboacylation of Olefins: a C–C Bond Activation Approach for Accessing FusedRing Systems. Angew. Chem. Int. Ed. 2012, 51, 7567-7571. (6) (a) Lei, Z. Q.; Pan, F.; Li, H.; Li, Y.; Zhang, X. S.; Chen, K.; Wang, X.; Li, Y. X.; Sun, J.; Shi, Z. J., Group Exchange between Ketones and Carboxylic Acids through Directing Group Assisted Rh-Catalyzed Reorganization of Carbon Skeletons. J. Am. Chem. Soc. 2015, 137, 5012-5020; (b) Lei, Z. Q.; Li, H.; Li, Y.; Zhang, X. S.; Chen, K.; Wang, X.; Sun, J.; Shi, Z. J., Extrusion of CO from Aryl Ketones: Rhodium(I)-Catalyzed C–C Bond Cleavage Directed by a Pyridine Group. Angew. Chem. Int. Ed. 2012, 51, 2690-2694; (c) Chen, K.; Li, H.; Lei, Z. Q.; Li, Y.; Ye, W. H.; Zhang, L. S.; Sun, J.; Shi, Z. J., Reductive Cleavage of the Csp2–Csp3 Bond of Secondary Benzyl Alcohols: Rhodium Catalysis Directed by N-Containing Groups. Angew. Chem. Int. Ed. 2012, 51, 9851-9855; (d) Li, H.; Li, Y.; Zhang, X. S.; Chen, K.; Wang, X.; Shi, Z. J., Pyridinyl Directed Alkenylation with Olefins via Rh(III)-catalyzed C–C Bond Cleavage of Secondary Arylmethanols. J. Am. Chem. Soc. 2011, 133, 15244-15247. (7) Selected examples: (a) Onodera, S.; Ishikawa, S.; Kochi, T.; Kakiuchi, F., Direct Alkenylation of Allylbenzenes via ChelationAssisted C–C Bond Cleavage. J. Am. Chem. Soc. 2018, 140, 97889792; (b) Keske, E. C.; West, T. H.; Lloyd-Jones, G. C., Analysis of



Autoinduction, Inhibition, and Autoinhibition in a Rh-Catalyzed C–C Cleavage: Mechanism of Decyanative Aryl Silylation. ACS Catal. 2018, 8, 8932-8940; (c) Ozkal, E.; Cacherat, B.; Morandi, B., Cobalt(III)-Catalyzed Functionalization of Unstrained Carbon–Carbon Bonds through β-Carbon Cleavage of Alcohols. ACS Catal. 2015, 5, 6458-6462; (d) Souillart, L.; Parker, E.; Cramer, N., Highly Enantioselective Rhodium(I)-Catalyzed Activation of Enantiotopic Cyclobutanone C–C Bonds. Angew. Chem. Int. Ed. 2014, 53, 3001-3005; (e) Souillart, L.; Cramer, N., Highly Enantioselective Rhodium(I)-Catalyzed Carbonyl Carboacylations Initiated by C–C Bond Activation. Angew. Chem. Int. Ed. 2014, 53, 9640-9644; (f) Wang, J.; Chen, W.; Zuo, S.; Liu, L.; Zhang, X.; Wang, J., Direct Exchange of a Ketone Methyl or Aryl Group to Another Aryl Group through C–C Bond Activation Assisted by Rhodium Chelation. Angew. Chem. Int. Ed. 2012, 51, 12334-12338 (g) Gooßen, L. J.; Deng, G.; Levy, L. M., Synthesis of Biaryls via Catalytic Decarboxylative Coupling. Science 2006, 313, 662-664; (h) Okazawa, T.; Satoh, T.; Miura, M.; Nomura, M., Palladium-Catalyzed Multiple Arylation of Thiophenes. J. Am. Chem. Soc. 2002, 124, 5286-5287, and cited references. (8) (a) Yan, M.; Kawamata, Y.; Baran, P. S., Synthetic Organic Electrochemistry: Calling All Engineers. Angew. Chem. Int. Ed. 2018, 57, 4149-4155; (b) Wiebe, A.; Gieshoff, T.; Mohle, S.; Rodrigo, E.; Zirbes, M.; Waldvogel, S. R., Electrifying Organic Synthesis. Angew. Chem. Int. Ed., 2018, 57, 5594-5619; (c) Waldvogel, S. R.; Lips, S.; Selt, M.; Riehl, B.; Kampf, C. J., Electrochemical Arylation Reaction. Chem. Rev. 2018, 118, 67066765; (d) Tang, S.; Liu, Y.; Lei, A., Electrochemical Oxidative Cross-coupling with Hydrogen Evolution: A Green and Sustainable Way for Bond Formation. Chem 2018, 4, 27-45; (e) Mohle, S.; Zirbes, M.; Rodrigo, E.; Gieshoff, T.; Wiebe, A.; Waldvogel, S. R., Modern Electrochemical Aspects for the Synthesis of Value-Added Organic Products. Angew. Chem. Int. Ed. 2018, 57, 6018-6041; (f) Lin, S.; Parry, J.; Fu, N., Electrocatalytic Difunctionalization of Olefins as a General Approach to the Synthesis of Vicinal Diamines. Synlett 2018, 29, 257-265; (g) Yan, M.; Kawamata, Y.; Baran, P. S., Synthetic Organic Electrochemical Methods Since 2000: On the Verge of a Renaissance. Chem. Rev. 2017, 117, 13230-13319; (h) Hou, Z.-W.; Mao, Z.-Y.; Xu, H.-C., Recent Progress on the Synthesis of (Aza)indoles through Oxidative Alkyne Annulation Reactions. Synlett 2017, 28, 1867-1872; (i) Feng, R.; Smith, J. A.; Moeller, K. D., Anodic Cyclization Reactions and the Mechanistic Strategies That Enable Optimization. Acc. Chem. Res. 2017, 50, 2346-2352; (j) Horn, E. J.; Rosen, B. R.; Baran, P. S., Synthetic Organic Electrochemistry: An Enabling and Innately Sustainable Method. ACS Cent. Sci. 2016, 2, 302-308; (k) Yoshida, J.; Kataoka, K.; Horcajada, R.; Nagaki, A., Modern Strategies in Electroorganic Synthesis. Chem. Rev. 2008, 108, 2265-2299; (l) Jutand, A., Contribution of Electrochemistry to Organometallic Catalysis. Chem. Rev. 2008, 108, 2300-2347. (9) (a) Ye, K. Y.; Song, Z.; Sauer, G. S.; Harenberg, J. H.; Fu, N.; Lin, S., Synthesis of Chlorotrifluoromethylated Pyrrolidines by Electrocatalytic Radical Ene-Yne Cyclization. Chem. Eur. J. 2018, 24, 12274-12279; (b) Ye, K. Y.; Pombar, G.; Fu, N.; Sauer, G. S.; Keresztes, I.; Lin, S., Anodically Coupled Electrolysis for the Heterodifunctionalization of Alkenes. J. Am. Chem. Soc. 2018, 140, 2438-2441; (c) Sauer, G. S.; Lin, S., An Electrocatalytic Approach to the Radical Difunctionalization of Alkenes. ACS Catal. 2018, 8, 5175-5187; (d) Cai, C.-Y.; Xu, H.-C., Dehydrogenative Reagent-free Annulation of Alkenes with Diols for the Synthesis of Saturated O-Heterocycles. Nat. Commun. 2018, 9, 3551; (e) Fu, N. S., G. S.; Saha, A.; Loo, A.; Lin, S., MetalCatalyzed Electrochemical Diazidation of Alkenes. Science 2017, 357, 575-579; (f) Fu, N.; Sauer, G. S.; Lin, S., Electrocatalytic

Page 8 of 10

Radical Dichlorination of Alkenes with Nucleophilic Chlorine Sources. J. Am. Chem. Soc. 2017, 139, 15548-15553. (10) (a) Wang, F.; Rafiee, M.; Stahl, S. S., Electrochemical Functional-Group-Tolerant Shono-type Oxidation of Cyclic Carbamates Enabled by Aminoxyl Mediators. Angew. Chem. Int. Ed. 2018, 57, 6686-6690; (b) Kawamata, Y.; Yan, M.; Liu, Z.; Bao, D. H.; Chen, J.; Starr, J. T.; Baran, P. S., Scalable, Electrochemical Oxidation of Unactivated C–H Bonds. J. Am. Chem. Soc. 2017, 139, 7448-7451; (c) Horn, E. J.; Rosen, B. R.; Chen, Y.; Tang, J.; Chen, K.; Eastgate, M. D.; Baran, P. S., Scalable and Sustainable Electrochemical Allylic C–H Oxidation. Nature 2016, 533, 77-81. (11) (a) Liu, K.; Song, C.; Lei, A., Recent Advances in Iodine Mediated Electrochemical Oxidative Cross-Coupling. Org. Biomol. Chem. 2018, 16, 2375-2387; (b) Lips, S.; Schollmeyer, D.; Franke, R.; Waldvogel, S. R., Regioselective Metal- and ReagentFree Arylation of Benzothiophenes by Dehydrogenative Electrosynthesis. Angew. Chem. Int. Ed. 2018, 40, 13325-13329; (c) Imada, Y.; Rockl, J. L.; Wiebe, A.; Gieshoff, T.; Schollmeyer, D.; Chiba, K.; Franke, R.; Waldvogel, S. R., Metal- and Reagent-Free Dehydrogenative Formal Benzyl-Aryl Cross-Coupling by Anodic Activation in 1,1,1,3,3,3-Hexafluoropropan-2-ol. Angew. Chem. Int. Ed. 2018, 57, 12136-12140; (d) Wiebe, A.; Lips, S.; Schollmeyer, D.; Franke, R.; Waldvogel, S. R., Single and Twofold Metal- and Reagent-Free Anodic C–C Cross-Coupling of Phenols with Thiophenes. Angew. Chem. Int. Ed. 2017, 56, 14727-14731; (e) Schulz, L.; Enders, M.; Elsler, B.; Schollmeyer, D.; Dyballa, K. M.; Franke, R.; Waldvogel, S. R., Reagent- and Metal-Free Anodic C– C Cross-Coupling of Aniline Derivatives. Angew. Chem. Int. Ed. 2017, 56, 4877-4881; (f) Li, C. K., Y.; Nakamura, H.; Vantourout, J. C.; Liu, Z.; Hou, Q.; Bao, D.; Starr, J. T.; Chen, J.; Yan, M.; Baran, P. S., Electrochemically Enabled, Nickel-Catalyzed Amination. Angew. Chem. Int. Ed. 2017, 56, 13088-13093; (g) Gieshoff, T.; Kehl, A.; Schollmeyer, D.; Moeller, K. D.; Waldvogel, S. R., Insights into the Mechanism of Anodic N–N Bond Formation by Dehydrogenative Coupling. J. Am. Chem. Soc. 2017, 139, 1231712324. For reductive couplings, see: (h) Gomes, P.; Gosmini, C.; Nédélec, J.-Y.; Périchon, J., Electrochemical Vinylation of Aryl and Vinyl Halides with Acrylate Esters Catalyzed by Cobalt Bromide. Tetrahedron Lett. 2002, 43, 5901-5903; (i) Gomes, P.; Gosmini, C.; Périchon, J., Cobalt-Catalyzed Direct Electrochemical Cross-Coupling between Aryl or Heteroaryl Halides and Allylic Acetates or Carbonates. J. Org. Chem. 2003, 68, 1142-1145, and cited references. (12) Peterson, B. M.; Lin, S.; Fors, B. P., Electrochemically Controlled Cationic Polymerization of Vinyl Ethers. J. Am. Chem. Soc. 2018, 140, 2076-2079. (13) (a) Yang, Q.-L.; Fang, P.; Mei, T.-S., Recent Advances in Organic Electrochemical C–H Functionalization. Chin. J. Chem. 2018, 36, 338-352; (b) Sauermann, N.; Meyer, T. H.; Qiu, Y.; Ackermann, L., Electrocatalytic C–H Activation. ACS Catal. 2018, 8, 7086-7103; (c) Sauermann, N.; Meyer, T. H.; Ackermann, L., Electrochemical Cobalt-Catalyzed C–H Activation. Chem. Eur. J. 2018, 24, 16209-16217; (d) Ma, C.; Fang, P.; Mei, T.-S., Recent Advances in C–H Functionalization Using Electrochemical Transition Metal Catalysis. ACS Catal. 2018, 8, 7179-7189; (e) Karkas, M. D., Electrochemical Strategies for C–H Functionalization and C–N Bond Formation. Chem. Soc. Rev. 2018, 47, 5786-5865; (f) Jiao, K.-J.; Zhao, C.-Q.; Fang, P.; Mei, T.S., Palladium Catalyzed C–H Functionalization with Electrochemical Oxidation. Tetrahedron Lett. 2017, 58, 797-802. (14) (a) Shrestha, A.; Lee, M.; Dunn, A. L.; Sanford, M. S., Palladium-Catalyzed C–H Bond Acetoxylation via Electrochemical Oxidation. Org. Lett. 2018, 20, 204-207; (b) Yang, Q. L.; Li, Y. Q.; Ma, C.; Fang, P.; Zhang, X. J.; Mei, T.-S., Palladium-Catalyzed C(sp3)–H Oxygenation via Electrochemical Oxidation. J. Am. Chem. Soc. 2017, 139, 3293-3298; (c) Ma, C.;


Page 9 of 10 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


Zhao, C. Q.; Li, Y. Q.; Zhang, L. P.; Xu, X. T.; Zhang, K.; Mei, T.S., Palladium-catalyzed C–H Activation/C–C Cross-Coupling Reactions via Electrochemistry. Chem. Commun. 2017, 53, 1218912192; (d) Li, Y. Q.; Yang, Q. L.; Fang, P.; Mei, T. S.; Zhang, D., Palladium-Catalyzed C(sp2)–H Acetoxylation via Electrochemical Oxidation. Org. Lett. 2017, 19, 2905-2908; (e) Konishi, M.; Tsuchida, K.; Sano, K.; Kochi, T.; Kakiuchi, F., PalladiumCatalyzed ortho-Selective C–H Chlorination of Benzamide Derivatives under Anodic Oxidation Conditions. J. Org. Chem. 2017, 82, 8716-8724; (f) Saito, F.; Aiso, H.; Kochi, T.; Kakiuchi, F., Palladium-Catalyzed Regioselective Homocoupling of Arenes Using Anodic Oxidation: Formal Electrolysis of Aromatic Carbon–Hydrogen Bonds. Organometallics 2014, 33, 6704-6707; (g) Aiso, H.; Kochi, T.; Mutsutani, H.; Tanabe, T.; Nishiyama, S.; Kakiuchi, F., Catalytic Electrochemical C–H Iodination and onepot Arylation by ON/OFF Switching of Electric Current. J. Org. Chem. 2012, 77, 7718-7724; (h) Kakiuchi, F. K., T.; Mutsutani, H.; Kobayashi, N.; Urano, S.; Sato, M.; Nishiyama, S.; Tanabe, T., Palladium-Catalyzed Aromatic C–H Halogenation with Hydrogen Halides by Means of Electrochemical Oxidation. J. Am. Chem. Soc. 2009, 131, 11310-11311; (i) Amatore, C.; Cammoun, C.; Jutand, A., Electrochemical Recycling of Benzoquinone in the Pd/Benzoquinone-Catalyzed Heck-Type Reactions from Arenes. Adv. Synth. Catal. 2007, 349, 292-296. (15) (a) Tian, C.; Massignan, L.; Meyer, T. H.; Ackermann, L., Electrochemical C–H/N–H Activation by Water-Tolerant Cobalt Catalysis at Room Temperature. Angew. Chem. Int. Ed. 2018, 57, 2383-2387; (b) Tang, S.; Wang, D.; Liu, Y.; Zeng, L.; Lei, A., Cobalt-Catalyzed Electrooxidative C–H/N–H [4+2] Annulation with Ethylene or Ethyne. Nat. Commun. 2018, 9, 798; (c) Sauermann, N.; Mei, R.; Ackermann, L., Electrochemical C–H Amination by Cobalt Catalysis in a Renewable Solvent. Angew. Chem. Int. Ed. 2018, 57, 5090-5094; (d) Meyer, T. H.; Oliveira, J. C. A.; Sau, S. C.; Ang, N. W. J.; Ackermann, L., Electrooxidative Allene Annulations by Mild Cobalt-Catalyzed C–H Activation. ACS Catal. 2018, 9140-9147; (e) Mei, R.; Sauermann, N.; Oliveira, J. C. A.; Ackermann, L., Electroremovable Traceless Hydrazides for Cobalt-Catalyzed Electro-Oxidative C–H/N–H Activation with Internal Alkynes. J. Am. Chem. Soc. 2018, 140, 7913-7921; (f) Gao, X.; Wang, P.; Zeng, L.; Tang, S.; Lei, A., Cobalt(II)-Catalyzed Electrooxidative C–H Amination of Arenes with Alkylamines. J. Am. Chem. Soc. 2018, 140, 4195-4199; (g) Sauermann, N.; Meyer, T. H.; Tian, C.; Ackermann, L., Electrochemical Cobalt-Catalyzed C–H Oxygenation at Room Temperature. J. Am. Chem. Soc. 2017, 139, 18452-18455. (16) (a) Qiu, Y.; Tian, C.; Massignan, L.; Rogge, T.; Ackermann, L., Electrooxidative Ruthenium-Catalyzed C–H/O–H Annulation by Weak O-Coordination. Angew. Chem. Int. Ed. 2018, 57, 58185822; (b) Xu, F.; Li, Y.-J.; Huang, C.; Xu, H.-C., RutheniumCatalyzed Electrochemical Dehydrogenative Alkyne Annulation. ACS Catal. 2018, 8, 3820-3824. (c) Mei, R.; Koeller, J.; Ackermann, L., Electrochemical ruthenium-catalyzed alkyne annulations by C–H/Het–H activation of aryl carbamates or phenols in protic media. Chem. Commun. 2018, 54, 12879-12882. (17) Qiu, Y.; Kong, W. J.; Struwe, J.; Sauermann, N.; Rogge, T.; Scheremetjew, A.; Ackermann, L., Electrooxidative RhodiumCatalyzed C–H/C–H Activation: Electricity as Oxidant for CrossDehydrogenative Alkenylation. Angew. Chem. Int. Ed. 2018, 57, 5828-5832.

(18) Qiu, Y. S., M.; Meyer, T. H.; Oliveira, J. C. A.; Ackermann, L., Iridium-Catalyzed Electrooxidative C–H Activation by Chemo-Selective Redox-Catalyst Cooperation. Angew. Chem. Int. Ed. 2018, 57, 14179– 14183. (19) (a) Yang, Q. L.; Wang, X. Y.; Lu, J. Y.; Zhang, L. P.; Fang, P.; Mei, T.-S., Copper-Catalyzed Electrochemical C–H Amination of Arenes with Secondary Amines. J. Am. Chem. Soc. 2018, 140, 11487-11494. (b) Zhang, S.-K.; Samanta, R. C.; Sauermann, N.; Ackermann, L., Nickel-Catalyzed Electrooxidative C−H Amination: Support for Nickel(IV). Chem. Eur. J. 2018, 24, 1916619170. (20) (a) Wang, H.; Choi, I.; Rogge, T.; Kaplaneris, N.; Ackermann, L., Versatile and Robust C–C Activation by Chelation-Assisted Manganese-Catalysis. Nature Catal. 2018, 1, 993-1001. (b) Moselage, M.; Li, J.; Kramm, F.; Ackermann, L., Ruthenium(II)-Catalyzed C-C Arylations and Alkylations: Decarbamoylative C-C Functionalizations. Angew. Chem. Int. Ed. 2017, 56, 5341-5344; (c) Kumar, N. Y. P.; Rogge, T.; Yetra, S. R.; Bechtoldt, A.; Clot, E.; Ackermann, L., Mild Decarboxylative C-H Alkylation: Computational Insights for Solvent-Robust Ruthenium(II) Domino Manifold. Chem. Eur. J. 2017, 23, 1744917453; (d) Kumar, N. Y. P.; Bechtoldt, A.; Raghuvanshi, K.; Ackermann, L., Ruthenium(II)-Catalyzed Decarboxylative C–H Activation: Versatile Routes to meta-Alkenylated Arenes. Angew. Chem. Int. Ed. 2016, 55, 6929-6932. (21) For detailed information, see Supporting Information. (22) (a) Davies, D. L.; Macgregor, S. A.; McMullin, C. L., Computational Studies of Carboxylate-Assisted C–H Activation and Functionalization at Group 8-10 Transition Metal Centers. Chem. Rev. 2017, 117, 8649-8709; (b) Ackermann, L., CarboxylateAssisted Transition-Metal-Catalyzed C–H Bond Functionalizations: Mechanism and Scope. Chem. Rev. 2011, 111, 1315-1345. (23) Boutadla, Y.; Davies, D. L.; Jones, R. C.; Singh, K., The Scope of Ambiphilic Acetate-Assisted Cyclometallation with Half-Sandwich Complexes of Iridium, Rhodium and Ruthenium. Chem. Eur. J. 2011, 17, 3438-3448. (24) (a) Lionetti, D.; Day, V. W.; Lassalle-Kaiser, B.; Blakemore, J. D., Multiple Binding Modes of an Unconjugated Bis(pyridine) Ligand Stabilize Low-Valent [Cp*Rh] Complexes. Chem. Commun. 2018, 54, 1694-1697; (b) Lionetti, D.; Day, V. W.; Blakemore, J. D., Synthesis and Electrochemical Properties of Half-Sandwich Rhodium and Iridium Methyl Complexes. Organometallics 2017, 36, 1897-1905; (c) Gusev, O. V.; Denisovich, L. I.; Peterleitner, M. G.; Rubezhov, A. Z.; Ustynyuk, N. A., Electrochemical Generation of 19-and 20-Electron Rhodocenium Complexes and their Properties. J. Organomet. Chem. 1993, 452, 219-222; (d) Ustynyuk, N. A.; Peterleitner, M. G.; Gusev, O. V.; Denisovich, L. I., Redox Properties of Rhodium Diene-Cyclopentadienyl Complexes. Russ. Chem. Bull. 1993, 42, 1727-1730; (e) Amouri , H. E.; Gruselle, M.; Jaouén, G., Bis[Dichloro(η-pentamethylcyclopentadienyl)rhodium(III) and iridium(III)] from bis[Chloro(1, 5-cyclooctadiene)rhodium(I) and -iridium(I)] Oxidation, and Formation of 1, 5-Cyclooctadiene(ηpentamethylcyclopentadienyl)rhodium(I). Synth. React. Inorg. and Met.-Org. Chem. 1994, 24, 395-400.



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Graphic Abstract Electrochemical C–C Activation rDG R

O R1

H R

rDG

Pt

RVC

H

2

+

R3

Rh

R

electrocatalytic C–C activation rhodium catalysis no Cu(II), or Ag(I) mechanistic insights electricity as green oxidant


R3 + H2

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