Transition-Metal-Free Oxidative Decarboxylative Cross Coupling of Î±

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Transition-Metal-Free Oxidative Decarboxylative Cross Coupling of alpha, beta-Unsaturated Carboxylic Acids with Cyclic Ethers under Air Conditions: Mild Synthesis of alpha-Oxyalkyl Ketones Peng-Yi Ji, Yu-Feng Liu, Jing-Wen Xu, Wei-Ping Luo, Qiang Liu, and Can-Cheng Guo J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.6b02993 • Publication Date (Web): 22 Feb 2017 Downloaded from http://pubs.acs.org on February 23, 2017

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The Journal of Organic Chemistry

Transition-Metal-Free Oxidative Decarboxylative Cross Coupling of α, βUnsaturated Carboxylic Acids with Cyclic Ethers under Air Conditions: Mild Synthesis of α-Oxyalkyl Ketones Peng-Yi Ji, Yu-Feng Liu, Jing-Wen Xu, Wei-Ping Luo, Qiang Liu, Can-Cheng Guo* College of Chemistry and Chemical Engineering, Advanced Catalytic Engineering Research Center of the Ministry of Education, Hunan University, Changsha 410082, China E-mail: [email protected]

ABSTRACT O R

X OH

+

H

O

K2S2O8 (2 equiv)

O (solvent)

100 oC, 12h

R

X O

+

CO2

Air

X = CH2, CH2CH2, CH2O, O

transition metal f ree decarboxylation 18 exmples, up to 92% yields under air condition

A novel K2S2O8 promoted decarboxylative cross coupling of α, β-unsaturated carboxylic acids with cyclic ethers was developed under aerobic conditions. The present protocol, which included C-C and C=O bond formation in one step through addition, oxidation and decarboxylation processes, leading to the desired ketone products in moderate to excellent yields. In addition, mechanism researches showed that the transformation process undergone a radical pathway via a direct activation of α-sp3 C-H bond of oxygen of cyclic ether. INTRODUCTION The construction of C-C, C-O and C=O bond have resulted in main characters in synthetic purpose and chemistry industrial through numerous synthetic approaches.1

ACS Paragon Plus Environment


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Among these brilliant avenues, decarboxylative coupling reactions, in which contain CO2 releasing from metal carboxylates to afford classic organometallic species which can efficiently conduct coupling reactions with other organic reagents under transition-metal-catalyzed conditions, show a great application potentiality in area of C-C bond formation.2 Therefore, during the last few decades, a large number of researchers laid their eyes on the research of transition metal catalytic C-C bond formation from carboxylic acid derivatives and other counterparts.3 Specially, indeed, In 2014, zhang et al. disclosed a nickel- and manganese-catalyzed selective decarboxylative cross coupling reactions with TBHP as additive oxidant and DBU as base.4 However, most actualities indicated that the use of transition-metal catalysts might not be considered the most ideal ones in pharmaceutical industry, since most of them are limited by its toxic traits, sensitive characters under aerobic atmosphere, and its essential connections with some special additives or cocatalysts.5 In these cases, making more significant efforts on exploiting transition-metal-free coupling reactions to construct sustainable developing model in C-C bond formation becomes an inevitable trend. As a result, along with the continuously breakthrough in science and technology, numerous practices and coupling reactions which are tagged to transition-metal-free conditions have been sought out,6 such as DDQ-promoted oxidative coupling reactions,7 organocatalytic or organophotoredox catalytic reactions,8 Hypervalent Iodine Reagents (HIR) promoted coupling reactions9 etc. However, transiton-metalfree decarboxylative reactions especially oxidative decarboxylative coupling reactions of α, β-unsaturated carboxylic acids to form industrial useful ketones are still rarely reported at present.4,10 Therein, as well as the steadfast endeavors of our laboratory about decarboxylative coupling reactions,11 we now wish to report the first highly


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efficient and K2S2O8 facilitated one step C-C and C=O bond formation from α, βunsaturated carboxylic acid with cyclic ether via oxidative coupling and decarboxylative reactions under air atmosphere. RESULTS AND DISCUSSION Inspired by this comforting reactivity pattern, the coupling of the cinnamic acid (1a) with tetrahydrofuran (THF, 2a) was chosen as a model reaction for the optimization of reaction conditions (Table 1). Initially, the efficiency of different anions and cations which constituted the external oxidant was tested under thermal conditions (entries 1-4, Table 1). And then treatment of the substrates with organic dioxide compound DTBP gave only 23% yields of the desired products 3aa (entry 5, Table 1), however, it was worthy to note that 34% yields of alkene product were obtained at the same time which was partly consisted with the results of Sun’s work.10a The yields of desired ketones improved onto 88% with trace amount of aldehyde byproduct when the temperature was raised up to 100 oC (entry 6, Table 1). Predictably, trying to decrease the amounts of peroxide had no good for the reaction activities (entry 7, Table 1). In order to understood whether other solvent such as water could influence this reaction system under aerobic conditions, we mixed THF with water in different proportions, and found that the reaction activities had been deactivated to different extent, which might imply that the solvent effect of water was not conducive to the transformation of model substrates (entries 8-9, Table 1). For a further study, the reaction was carried out under O2 for 12h, but the yields of desired product decreased to 83%, and the TLC results showed that the reaction was more complicatedly than it was carried out under air conditions (entry 10, Table 1). Notably, only 15% yields were obtained without the presence of peroxides indicated that the appropriate amount of oxidant was necessary for a better reaction activity (entry 11, Table 1).



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Table 1. Optimization of the Reaction Conditions for 3aaa

a

Entry oxidant

temperature/oC solvent

1

K2S2O8

80

THF

70

2

Na2S2O8

80

THF

35

3

(NH4)2S2O8

80

THF

30

4

KHSO5

80

THF

65

5

DTBP

80

THF

23

6

K2S2O8

100

THF

88

7

K2S2O8 (1 equiv) 100

THF

68

8

K2S2O8

100

THF/H2O (100:1)

49

9

K2S2O8

100

THF/H2O (1:1)

10b

K2S2O8

100

THF

83

11b

-

100

THF

15

yield/%

trace

General reaction conditions unless otherwise pointed: 1 (0.2 mmol), 2a (1.5 ml),

K2S2O8 (0.4 mmol, 2 equiv) at 100 oC under air for 12 h. b under O2 for 12 h. With the optimized conditions in hand, the generality and scope of substrates were examined (Table 2). Both halogen and electron-rich or -deficient aryl-substituented cinnamic acids could be smoothly transformed in a range of 34-92% yields (3aa-3ga). A series of functional groups at meta-position of the aryl ring were also toleranted well in these oxidative decarboxylative cross coupling reactions (3ha-3ja). Then, several ortho-subtituented cinnamic acids except OH group still showed moderate to good efficiency in these C-C and C=O bond formations (3ka-3na). Part of the reason


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for various compatibility and reactivity might be that the electronic effects of different substitutents on phenyl ring could influence the reaction activities of α, β-unsaturated carboxylic acids. Furthermore, notably, the position of the substituents at aryl ring could influence the efficiency of this transformation. For instance, methoxy-group at meta-position gave a better transformation efficiency than it at ortho-/para-position, probably because of the electronic effect of methoxy-group impacted the reaction activities(3ea, 3ha, 3ka). For the heterocyclic derivatives, only (E)-3-(thiophen-2yl)acrylic acid successfully transformed into corresponding products, and obtained in 45% yields (3oa-3ra), which indicated that the influence of the heteroatoms in aromatic ring was not negligible. Moreover, it was found that both (2E,4E)-hexa-2,4dienoic acid 3sa and (E)-hex-2-enoic acid 3ta were not amenable to the present transformation even under O2 for 15h. Table 2. Scope of α, β-Unsaturated Carboxylic Acidsa



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a

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General reaction conditions unless otherwise pointed: 1 (0.2 mmol), 2a (1.5 ml),

K2S2O8 (0.4 mmol, 2 equiv) at 100 oC under air for 12 h, yield of isolated product.

b

under O2 for 15 h. Subsequently, we tested the scope of heterocyclic compounds (Table 3). When pentabasic cyclic compounds such as tetrahydrofuran, tetrahydrothiophene and 1methylpyrrolidine were employed as substrates, it was found that only when the C(sp3)-H bond adjacent to oxygen atom, the heterocyclic compounds could be activated successfully under the standard conditions, which might also implied that heteroatoms in heterocyclic compounds played a leadership role in this activation process (3aa-3ac). Then, other cyclic ether like 1,3-dioxolane and benzo[d]-


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[1,3]dioxole were investigated, and the desired product 3ad were obtained in 52%, but benzo[d]-[1,3]dioxole was failed yet to give the product 3ae. Fortunately, hexatomic cyclic ethers coupled well with cinnamic acids to give the corresponding products in 71-63% yields (3af-3ag). Linear ethers, such as dibutyl ether 3ah, are failed to take part into this kind of transformation. Table 3. Scope of Cyclic or Linear Coupling Componenta

a

General reaction conditions unless otherwise pointed: 1a (0.2 mmol), 2 (1.5 ml),

K2S2O8 (0.4 mmol, 2 equiv) at 100 oC under air for 12 h, yield of isolated product. b reacted at 110 oC under air for 15 h. For the possible reaction mechanism of the decarboxylative coupling process, several control experiments were carried out at the beginning (Scheme 1). Initially, 2 equiv of the radical scavenger, such as 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) or butylated hydroxytoluene (BHT), were added into the reaction mixture respectively, the model reaction was not transformed successfully according to the results of TLC and GC-MS (Scheme 1a-b), which made clear a radical process was included in this decarboxylative coupling reaction. Delightfully, trace amount of the free radical



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intermediate species 4 was detected by GC-MS, which impelled us to interpret the reaction was able to conduct via a direct activation of α-sp3 C-H bond of oxygen under nitrogen conditions (Scheme 1c, for details, see Supporting Information). No reaction products occurred and no styrene was obtained when cinnamic acid was employed as the substrate only (Scheme 1d), furthermore, we employed styrene and tetrahydrofuran as the substrates under standard conditions, and no desired products 3aa were detected (Scheme 1e). The results thus obtained showed that styrene might not take a part in this decarboxylative cross coupling process of the model transformation. While the model reaction was conducted under N2 for 12h, no desired ketone products 3aa were obtained, and the recovery rate of material was about 90%. It should be pointed out that trace amount of the alkenylation product was formed under the standard reaction conditions, which might indicate that the dioxygen was indispensable for the model transformation and was likely to act as an important role for the origin of ketone oxygen (Scheme 1f, for more details see Scheme S2.1 in Supporting Information). Subsequently, the model reaction was conducted under O2 without the existence of the K2S2O8 for 24h, to our surprise, about 16% yields of 3aa and 8% yields of the alkylation product 3aa’ were formed, and we wondered whether the alkylation compound 3aa’ was one of the intermediates to form the final ketone product, then the alkylation compound was employed as the reaction agent under air or N2 with 1 equiv of the oxidant, but no ketone products were obtained, according to these, we believed that the alkylation compound might not act as an intermediate compound for the formation of 3aa under the standard conditions (for more details, see Scheme S2.2 in Supporting Information). Scheme 1. Experiments for Mechanism


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On the basis of the experiments mentioned above and preterit literatures,12 and in contrast to the work which selectively formed ketones via the ineluctable produce of Ni(II) carboxylate salt intermidiates,4 a possible inequable radical pathway of the decarboxylative coupling reactions under transiton-metal-free conditions is proposed (scheme 2). At the beginning, hydrogen abstraction of 2a generates α-oxyalkyl radical A with the existence of K2S2O8 under thermal conditions.13 After a radical addition of A to cinnamic acid 1a and direct O2 trapping process, then produces peroxide radical B which could potentially undergo a decomposition process to form radical intermediate C.12a,d Thereafter, a subsequent oxidation of C might adopt to form D. Finally, compound D via a cyclization-decarboxylation-aromatization process14 under



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the standard conditions, produces E (for details, see Scheme S2.1 in Supporting Information), which isomerizes and forms product 3aa. In addition, further researches are still on the way for clarifying detailed mechanisms and underway by our group. Scheme 2. Possible Mechanism

CONCLUSIONS From

above

all,

a

novel

K2S2O8-mediated

oxidative

decarboxylative

oxyalkylation of α, β-unsaturated carboxylic acids and cyclic ethers via selective activation of α-sp3 C-H bonds of oxygen to construct new C-C bonds and C=O bonds has been systematic researched. Prudently, it also invites us to utilize and improve these particular protocols and potential synthetic utility in modern organic synthesis. The vast field and mechanism of radical decarboxylative couplings with cyclic ethers in the presence of 2 equiv of K2S2O8 under mild aerobic conditions has been appropriately discussed as well. More oxidative decarboxylative coupling reactions and a broader application of transition-metal-free conditions thus mentioned above will be continuously exploited by our group. EXPERIMENTAL SECTION


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General Comments. All available compounds were purchased from commercial suppliers, and the compounds were used without further purification unless otherwise noted. All solvents were purified according to the method of Grubbs.15 1H NMR and 13

C NMR spectra were recorded at 400 and 100 MHz in CDCl3 using TMS as the

internal standard. Multiplicities were indicated as s (singlet), d (doublet), t (triplet), q (quartet), and m (multiplet). Coupling constants (J) were reported in hertz. Copies of 1

H NMR and

13

chromatography

C NMR spectra were provided as Supporting Information. Column was

performed

on

300−400

mesh

silica

gel.

Thinlayer

chromatography (TLC) was performed on Silicycle 250 mm silica gel F-254 plates. High-resolution mass spectra (HRMS) were measured on a double focusing mass spectrometer with EI source. General Procedure for the Decarboxylative Coupling reaction between various α, β-Unsaturated Carboxylic Acids and THF: To a 20 mL Schlenk tube was added α, β-unsaturated carboxylic acid (0.2 mmol), K2S2O8 (90.8 mg, 0.4 mmol), tetrahydrofuran (1.5 ml). The reaction mixture was stirred at 100 oC for 12 h in sealed conditions. Upon completion of the reaction, the resulting mixture was dilute by EtOAc and washed with equal amounts of saturated NaHCO3 solution, then the organic phase was separated and washed with water, and the water phase was extracted by EtOAc for three times. The combined organic extracts thus obtained were dried over anhydrous Na2SO4 and filtered. Finally, after concentrated in vacuum, the resulting mixture was purified by silica gel column chromatography (hexane/ethyl acetate = 15:1) to afford the desired product. General Procedure for the Decarboxylative Coupling reaction between various Cyclic Coupling Components and Cinnamic Acid: To a 20 mL Schlenk tube was added cinnamic acid (0.2 mmol), K2S2O8 (90.8 mg, 0.4 mmol), cyclic coupling



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component (1.5 ml). The reaction mixture was stirred at 100 oC for 12 h in sealed conditions. Upon completion of the reaction, the resulting mixture was dilute by EtOAc and washed with equal amounts of saturated NaHCO3 solution, then the organic phase was separated and washed with water, and the water phase was extracted by EtOAc for three times. The combined organic extracts thus obtained were dried over anhydrous Na2SO4 and filtered. Finally, after concentrated in vacuum, the resulting mixture was purified by silica gel column chromatography (hexane/ethyl acetate = 15:1) to afford the desired product. 3-oxo-3-phenyl-2-(tetrahydrofuran-2-yl)propanoic acid (C). (new) Yellow oil: 1

H NMR (400 MHz, CDCl3) δ 8.04 – 7.96 (m, 1H), 7.58 – 7.55 (m, 1H), 7.52 – 7.45

(m, 2H), 4.30 – 4.23 (m, 1H), 3.94 – 3.88 (dd, J = 14.7, 7.3 Hz, 1H), 3.82 – 3.76 (dd, J = 14.7, 7.5 Hz, 1H), 2.63 – 2.56 (m, 1H), 2.16 – 2.08 (dt, J = 12.4, 6.5 Hz, 1H), 1.95 – 1.91 (m, 2H), 1.62 – 1.53 (dt, J = 19.8, 7.7 Hz, 1H). 13C NMR (100 MHz, CDCl3) δ 25.5, 31.2, 40.2, 68.1, 75.0, 128.1, 128.6, 133.1, 137.0, 175.7, 199.9. HRMS (EI) Calcd for C13H14O4 (M+) 234.0892; Found, 234.0880. 1-phenyl-2-(tetrahydrofuran-2-yl)ethanone

(3aa).16b

Following

the

general

procedure, the product was isolated as yellow oil in 88% yields (33.4 mg). 1H NMR (400 MHz, CDCl3) δ: 7.97 (d, J = 7.7 Hz, 2H), 7.56 (t, J = 7.3 Hz, 1H), 7.46 (t, J = 7.5 Hz, 2H), 4.44 – 4.38 (m, 1H), 3.91– 3.87 (dd, J = 14.6, 7.2 Hz, 1H), 3.76 – 3.75 (dd, J = 14.8, 7.4 Hz, 1H), 3.43 – 3.37 (dd, J = 16.3, 6.1 Hz, 1H), 3.09 – 3.03 (dd, J = 16.3, 6.7 Hz, 1H), 2.23 – 2.16 (dt, J = 13.0, 6.5 Hz, 1H), 1.98 – 1.88 (m, 2H), 1.61 – 1.52 (m, 1H).

13

C NMR (100 MHz, CDCl3) δ: 25.6, 31.6, 44.6, 67.8, 75.4, 128.2,

128.6, 133.1, 137.0, 198.4. 1-(4-fluorophenyl)-2-(tetrahydrofuran-2-yl)ethanone (3ba).

16b

Following the

general procedure, the product was isolated as yellow oil in 90% yields (37.4 mg).


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1

H NMR (400 MHz, CDCl3) δ: 8.01 – 7.98 (dd, J = 8.5, 5.5 Hz, 2H), 7.13 (t, J = 8.5

Hz, 2H), 4.44 – 4.35 (m, 1H), 3.90 – 3.86 (dd, J = 14.8, 7.0 Hz, 1H), 3.76 – 3.74 (dd, J = 14.8, 7.4 Hz, 1H), 3.37 – 3.33 (dd, J = 16.1, 6.3 Hz, 1H), 3.05 – 3.00 (dd, J = 16.1, 6.4 Hz, 1H), 2.22 – 2.16 (td, J = 12.8, 6.5 Hz, 1H), 1.98 – 1.89 (m, 2H), 1.62 – 1.53 (ddd, J = 16.1, 12.5, 7.9 Hz, 1H).

13

C NMR (100 MHz, CDCl3) δ: 25.5, 31.6, 44.5,

67.8, 75.3, 115.6 (d, JC-F = 22.0 Hz), 130.8 (d, JC-F = 9.3 Hz), 133.5 (d, JC-F = 3.0 Hz), 165.7 (d, JC-F = 254.0 Hz), 196.8. 1-(4-chlorophenyl)-2-(tetrahydrofuran-2-yl)ethanone (3ca).

16b

Following the

general procedure, the product was isolated as yellow oil in 92% yields (41.2 mg). 1

H NMR (400 MHz, CDCl3) δ: 7.90 (d, J = 8.2 Hz, 2H), 7.43 (d, J = 8.2 Hz, 2H), 4.42

– 4.35 (m, 1H), 3.90 – 3.88 (dd, J = 14.6, 7.3 Hz, 1H), 3.78 –3.74 (dd, J = 14.9, 7.4 Hz, 1H), 3.37 – 3.31 (dd, J = 16.2, 6.3 Hz, 1H), 3.03 – 2.99 (dd, J = 16.2, 6.3 Hz, 1H), 2.22 – 2.15 (td, J = 12.8, 6.5 Hz, 1H), 1.98 – 1.88 (m, 2H), 1.61 – 1.52 (dq, J = 12.5, 8.0 Hz, 1H). 13C NMR (100 MHz, CDCl3) δ: 25.5 31.5, 44.5, 67.8, 75.3, 128.8, 129.6, 135.3, 139.5, 197.2. 1-(4-bromophenyl)-2-(tetrahydrofuran-2-yl)ethanone (3da).

16b

Following the



– 4.36 (m, 1H), 3.90 – 3.88 (dd, J = 14.7, 7.2 Hz, 1H), 3.78 – 3.76 (dd, J = 14.8, 7.4 Hz, 1H), 3.36 – 3.31 (dd, J = 16.1, 6.3 Hz, 1H), 3.05 – 2.99 (dd, J = 16.2, 6.3 Hz, 1H), 2.22 – 2.15 (dt, J = 12.9, 6.4 Hz, 1H), 1.97 – 1.90 (dt, J = 13.4, 6.9 Hz, 2H), 1.57 – 1.52 (dd, J = 14.2, 6.2 Hz, 1H). 13C NMR (100 MHz, CDCl3) δ: 25.6 31.6, 44.6, 67.9, 75.3, 128.3, 129.7, 131.9, 135.8, 197.5. 1-(4-methoxyphenyl)-2-(tetrahydrofuran-2-yl)ethanone (3ea).

16b

Following the




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1

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– 4.36 (m, 1H), 3.91 – 3.87 (m, 4H), 3.79 – 3.77 (m, 1H), 3.38 – 3.33 (dd, J = 15.9, 6.0 Hz, 1H), 3.03 – 2.98 (dd, J = 16.0, 6.8 Hz, 1H), 2.21 – 2.15 (dt, J = 19.1, 6.6 Hz, 1H), 1.97 – 1.88 (m, 2H), 1.62 – 1.55 (dd, J = 12.3, 8.0 Hz, 1H). 13C NMR (100 MHz, CDCl3) δ: 25.6, 31.6, 44.3, 55.7, 67.8, 75.6, 114.8, 130.2, 130.5, 163.5, 197.1. 1-(4-nitrophenyl)-2-(tetrahydrofuran-2-yl)ethanone

(3fa).(new)

Following

the



– 4.37 (m, 1H), 3.90 – 3.87 (dd, J = 14.8, 7.1 Hz, 1H), 3.77 – 3.75 (dd, J = 14.9, 7.4 Hz, 1H), 3.42 – 3.36 (dd, J = 16.2, 6.7 Hz, 1H), 3.13 – 3.04 (dd, J = 16.2, 5.8 Hz, 1H), 2.24 – 2.18 (td, J = 12.8, 6.5 Hz, 1H), 1.99 – 1.92 (m, 2H), 1.62 – 1.57 (m, 1H). 13C NMR (100 MHz, CDCl3) δ: 25.6, 31.6, 45.1, 68.0, 75.1, 123.8, 129.3, 141.5, 150.3, 197.1. HRMS (EI) Calcd for C12H13NO4 (M+) 235.0845; Found, 235.0840. 2-(tetrahydrofuran-2-yl)-1-(4-(trifluoromethyl)phenyl)ethanone

(3ga).

16c

Following the general procedure, the product was isolated as white solid in 34% yields (17.6 mg). 1H NMR (400 MHz, CDCl3) δ: 8.07 (d, J = 8.1 Hz, 2H), 7.73 (d, J = 8.2 Hz, 2H), 4.44 – 4.37 (m, 1H), 3.90 – 3.88 (m, 1H), 3.77 – 3.75 (dd, J = 14.9, 7.4 Hz, 1H), 3.42 – 3.36 (dd, J = 16.2, 6.4 Hz, 1H), 3.11 – 3.05 (dd, J = 16.2, 6.1 Hz, 1H), 2.23 – 2.17 (td, J = 12.8, 6.5 Hz, 1H), 1.98 – 1.91 (m, 2H), 1.63 – 1.54 (ddd, J = 16.0, 12.4, 8.0 Hz, 1H). 13C NMR (100 MHz, CDCl3) δ: 25.6, 31.6, 44.9, 67.9, 75.2, 122.2, 125.6 (q, JC-F = 3.6 Hz), 128.5, 134.5 (d, JC-F = 33 Hz) 139.7, 197.5. 1-(3-methoxyphenyl)-2-(tetrahydrofuran-2-yl)ethanone (3ha).

(new)

Following the


H NMR (400 MHz, CDCl3) δ: 7.54 (d, J = 7.6 Hz, 1H), 7.49 (s, 1H), 7.37 (t, J = 7.9

Hz, 1H), 7.12 – 7.09 (dd, J = 8.2, 2.4 Hz, 1H), 4.44 – 4.37 (m, 1H), 3.90 – 3.85 (m,


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4H), 3.76 – 3.74 (dd, J = 14.9, 7.4 Hz, 1H), 3.40 – 3.35 (dd, J = 16.2, 6.1 Hz, 1H), 3.07 – 3.02 (dd, J = 16.2, 6.7 Hz, 1H), 2.22 – 2.16 (td, J = 12.8, 6.5 Hz, 1H), 1.97 – 1.89 (m, 2H), 1.61 – 1.52 (ddd, J = 16.0, 12.4, 7.9 Hz, 1H). 13C NMR (100 MHz, CDCl3) δ: 25.6, 31.6, 44.7, 55.3, 67.8, 75.4, 112.2, 119.6, 120.8, 129.5, 138.4, 159.8, 198.2. HRMS (EI) Calcd for C13H16O3 (M+) 220.1099; Found, 220.1098. 2-(tetrahydrofuran-2-yl)-1-(m-tolyl)ethanone (3ia).

16b

Following the general

procedure, the product was isolated as brown oil in 79% yields (32.2 mg). 1

H NMR (400 MHz, CDCl3) δ: 7.76 (d, J = 9.9 Hz, 2H), 7.38 – 7.32 (m, 2H), 4.44 –

4.37 (m, 1H), 3.90 – 3.88 (dd, J = 14.8, 7.1 Hz, 1H), 3.78 – 3.74 (dd, J = 14.9, 7.4 Hz, 1H), 3.41 – 3.36 (dd, J = 16.2, 6.0 Hz, 1H), 3.07 – 3.01 (dd, J = 16.2, 6.8 Hz, 1H), 2.41 (s, 3H), 2.22 – 2.17 (dt, J = 12.6, 6.4 Hz, 1H), 1.97 – 1.90 (m, 2H), 1.61 – 1.52 (ddd, J = 16.1, 12.4, 7.9 Hz, 1H).

13

C NMR (100 MHz, CDCl3) δ: 21.3, 25.6, 31.6,

44.7, 67.8, 75.4, 125.4, 128.4, 128.7, 133.8, 137.1, 138.3, 198.6. 1-(3-bromophenyl)-2-(tetrahydrofuran-2-yl)ethanone (3ja).

(new)

Following the


H NMR (400 MHz, CDCl3) δ: 7.87 (s, 1H), 7.77 (d, J = 7.7 Hz, 1H), 7.46 (d, J = 7.9

Hz, 1H), 7.36 – 7.32 (t, J = 7.9 Hz, 1H), 4.36 – 4.29 (m, 1H), 3.82 (dd, J = 14.6, 7.3 Hz, 1H), 3.83 – 3.68 (dd, J = 14.9, 7.4 Hz, 1H), 3.30 – 3.25 (dd, J = 16.2, 6.3 Hz, 1H), 2.99 – 2.93 (dd, J = 16.2, 6.3 Hz, 1H), 2.15 – 2.09 (td, J = 12.8, 6.5 Hz, 1H), 1.90 – 1.83 (m, 2H), 1.50 – 1.45 (m, 1H). 13C NMR (100 MHz, CDCl3) δ: 25.6, 31.6, 44.7, 67.9, 75.2, 126.3, 128.3, 129.9, 133.0, 134.9, 138.6, 197.1. HRMS (EI) Calcd for C12H13BrO2 (M+) 268.0099; Found, 268.0103. 1-(2-methoxyphenyl)-2-(tetrahydrofuran-2-yl)ethanone (3ka).

16a

Following the




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1

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H NMR (400 MHz, CDCl3) δ 7.72 – 7.70 (dd, J = 7.6, 1.3 Hz, 1H), 7.45 – 7.43 (m,

1H), 7.02 – 6.95 (m, 2H), 4.40 – 4.29 (m, 1H), 3.90 – 3.86 (m, 4H), 3.74 – 3.72 (dd, J = 14.9, 7.4 Hz, 1H), 3.42 – 3.36 (dd, J = 16.8, 6.1 Hz, 1H), 3.17 – 3.11 (dd, J = 16.8, 6.9 Hz, 1H), 2.18 – 2.14 (m, 1H), 1.94 – 1.86 (m, 2H), 1.58 – 1.49 (m, 1H). 13C NMR (100 MHz, CDCl3) δ: 25.6, 31.5, 49.9, 55.4, 67.7, 75.4, 111.5, 120.7, 128.3, 130.4, 133.5, 158.6, 200.3. 1-(2-fluorophenyl)-2-(tetrahydrofuran-2-yl)ethanone (3ma).

16b

Following the


H NMR (400 MHz, CDCl3) δ: 7.87 (t, J = 7.4 Hz, 1H), 7.52 – 7.48 (dd, J = 13.3, 6.7

Hz, 1H), 7.22 (t, J = 7.5 Hz, 1H), 7.15 – 7.10 (dd, J = 10.8, 8.8 Hz, 1H), 4.45 – 4.38 (m, 1H), 3.89 – 3.85 (dd, J = 14.6, 7.2 Hz, 1H), 3.77 – 3.74 (dd, J = 14.7, 7.4 Hz, 1H), 3.33 – 3.31 (ddd, J = 17.0, 6.6, 2.4 Hz, 1H), 3.16 – 3.14 (ddd, J = 17.0, 5.7, 2.9 Hz, 1H), 2.20 – 2.16 (m, 1H), 1.95 – 1.90 (dd, J = 14.3, 7.3 Hz, 2H), 1.61 – 1.52 (m, 1H). 13

C NMR (100 MHz, CDCl3) δ: 25.6, 31.6, 49.5 (d, JC-F = 6.9 Hz), 67.8, 74.8 (d, JC-F

= 1.9 Hz), 116.6 (d, JC-F = 24 Hz), 124.4 (d, JC-F = 3.4 Hz), 125.7, 130.6 (d, JC-F = 2.5 Hz), 134.5 (d, JC-F = 9.0 Hz), 161.9 (d, JC-F = 253.0 Hz), 196.5 (d, JC-F = 3.8 Hz). 1-(2-chlorophenyl)-2-(tetrahydrofuran-2-yl)ethanone (3na).

16a

Following the


H NMR (400 MHz, CDCl3) δ: 7.51 – 7.50 (d, J = 7.5 Hz, 1H), 7.41 – 7.37 (t, J = 7.6

Hz, 2H), 7.35 – 7.30 (dd, J = 14.4, 7.2 Hz, 1H), 4.38 – 4.32 (p, J = 6.7 Hz, 1H), 3.87 – 3.84 (dd, J = 14.6, 7.3 Hz, 1H), 3.74 – 3.72 (dd, J = 14.8, 7.5 Hz, 1H), 3.31 – 3.25 (dd, J = 16.3, 6.9 Hz, 1H), 3.14 – 3.09 (dd, J = 16.3, 6.0 Hz, 1H), 2.18 – 2.13 (td, J = 12.7, 6.5 Hz, 1H), 1.95 – 1.90 (m, 2H), 1.62 – 1.53 (m, 1H). 13C NMR (100 MHz, CDCl3) δ: 25.6, 31.4, 48.9, 67.8, 75.1, 126.9, 129.1, 130.4, 130.8, 131.7, 139.4, 201.4.


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2-(tetrahydrofuran-2-yl)-1-(thiophen-2-yl)ethanone (3pa).

(new)

Following the

general procedure, the product was isolated as yellow oil in 45% yields (17.6 mg). 1H NMR (400 MHz, CDCl3) δ: 7.74 – 7.71 (dd, J = 7.2, 3.8 Hz, 1H), 7.64 (d, J = 4.9 Hz, 1H), 7.13 (t, J = 4.3 Hz, 1H), 4.42 – 4.35 (m, 1H), 3.90 – 3.87 (dd, J = 14.5, 7.2 Hz, 1H), 3.76 – 3.74 (dd, J = 14.8, 7.5 Hz, 1H), 3.33 – 3.27 (dd, J = 15.4, 6.3 Hz, 1H), 3.01 – 2.96 (dd, J = 15.2, 6.5 Hz, 1H), 2.17 (dt, J = 12.5, 6.5 Hz, 1H), 1.93 (dt, J = 10.3, 8.5 Hz, 2H), 1.84 – 1.75 (m, 1H).

13

C NMR (100 MHz, CDCl3) δ: 25.6, 31.5,

45.4, 67.9, 75.5, 128.1, 132.3, 133.8, 144.6, 191.1. HRMS (EI) Calcd for C10H12O2S (M+) 196.0558; Found, 196.0563. 2-(1,3-dioxolan-2-yl)-1-phenylethanone (3ad). 16b Following the general procedure, the product was isolated as yellow oil in 52% yields (20.0 mg). 1

H NMR (400 MHz, CDCl3) δ: 7.90 (d, J = 7.9 Hz, 2H), 7.50 (t, J = 7.2 Hz, 1H), 7.40

(t, J = 7.4 Hz, 2H), 5.38 (t, J = 4.8 Hz, 1H), 3.96 – 3.88 (m, 2H), 3.85 – 3.82 (m, 2H), 13

3.28 (d, J = 4.9 Hz, 2H).

C NMR (100 MHz, CDCl3) δ: 43.4, 65.0, 101.4, 128.3,

128.6, 133.3, 136.9, 196.5. 1-phenyl-2-(tetrahydro-2H-pyran-2-yl)ethanone (3af).

16b

Following the general

procedure, the product was isolated as yellow oil in 71% yields (29.0 mg). 1

H NMR (400 MHz, CDCl3) δ: 7.96 (d, J = 7.9 Hz, 2H), 7.56 (t, J = 7.2 Hz, 1H), 7.45

(t, J = 7.6 Hz, 2H), 3.98 – 3.93 (m, 2H), 3.48 (t, J = 11.2 Hz, 1H), 3.32 – 3.26 (dd, J = 16.0, 6.7 Hz, 1H), 2.95 – 2.90 (dd, J = 16.0, 5.7 Hz, 1H), 1.86 – 1.84 (m, 1H), 1.75 (d, J = 12.9 Hz, 1H), 1.60 – 1.50 (m, 3H), 1.41 – 1.33 (m, 1H).

13

C NMR (100 MHz,

CDCl3) δ: 23.4, 25.8, 32.0, 45.4, 68.6, 74.3, 128.2, 128.5, 133.0, 137.3, 198.4. 2-(1,4-dioxan-2-yl)-1-phenylethanone (3ag).

16b

Following the general procedure,

the product was isolated as yellow oil in 63% yields (26.0 mg).



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1

H NMR (400 MHz, CDCl3) δ 7.95 (d, J = 7.9 Hz, 2H), 7.58 (t, J = 7.2 Hz, 1H), 7.47

(t, J = 7.6 Hz, 2H), 4.28 – 4.22 (m, 1H), 3.93 – 3.89 (m, 1H), 3.80 – 3.71 (m, 3H), 3.66 – 3.60 (m, 1H), 3.39 (t, J = 10.6 Hz, 1H), 3.23 – 3.22 (dd, J = 16.5, 6.5 Hz, 1H), 2.92 – 2.86 (dd, J = 16.5, 6.0 Hz, 1H).

13

C NMR (100 MHz, CDCl3) δ: 40.7, 66.4,

66.8, 70.9, 71.8, 128.2, 128.6, 133.3, 136.8, 197.1. ASSOCIATED CONTENTS Supporting Information Copies of 1H and 13C spectra for all products and the mechanism-related experiments are available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]. Notes The authors declare no competing financial interest. Acknowledgements Financial supports from the National Science Foundations of China (No.21372068, 21572049) are gratefully acknowledged. REFERENCES (1) For some selected examples, see: (a) Ritleng, V.; Sirlin, C.; Pfeffer, M.; Chem. Rev. 2002, 102, 1731. (b) Beccalli, E. M.; Broggini, G.; Martinelli, M.; Sottocornola, S.; Chem. Rev. 2007, 107, 5318. (c) Cao, H.; Liu, X.; Liao, J.; Huang, J.; Qiu, H,; Chen, Q.; Chen, Y.; J. Org. Chem., 2014, 79, 11209. (d) Liu, Y.; Zhu, J.; Qian, J.; Xu, Z.; J. Org. Chem., 2012, 77, 5411. (2) For some selected examples, see: Rodriguez, N.; (a) Goossen, L. J.; Chem. Soc. Rev. 2011, 40, 5030. (b) Arun, J. B.; Yan, G.; Org. Biomol. Chem. 2015, 13, 8094.


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(9) For some selected examples, see: (a) Dohi, T.; Kita, Y.; Topics in Current Chemistry: Hypervalent Iodine Chemistry. 2016, 373, 1–24. (b) Xu, J. H.; Jiang, Q.; Guo, C. C.; J. Org. Chem. 2013, 78, 11881. (c) Purkait, N., Okumura, S.; Souto, J. A.; Muniz, K.; Org. Lett. 2014, 16, 4750. (d) Kiyokawa, K.; Yahata, S.; Kojima, T.; Minakata, S.; Org. Lett. 2014, 16, 4646. (e) Dohi, T.; Ito, M.; Morimoto, K.; Iwata, M.; Kita Y.; Angew. Chem. Int. Ed. 2008, 47, 1301. (10) (a) Ji, J.; Liu, P.; Sun, P.; Chem. Commun. 2015, 51, 7546. (b) Park, K.; Lee, S.; RSC Adv. 2013, 3, 14165. (c) Liu, L.; Zhang-Negrerie, D.; Du, Y.; Zhao, K.; Synthesis. 2015, 47, 2924. (d) Wang, J.; Wang, N.; Zhang, W.; Bai, C. B.; Li, Y. H.; Wen, J. L.; Synlett. 2014, 25, 1621. (11) (a) Jiang, Q.; Jia, J.; Xu, B.; Zhao, A.; Guo, C. C.; J. Org. Chem. 2015, 80, 3586. (b) Jiang, Q.; Xu, B.; Jia, J.; Zhao, A.; Zhao, Y. R.; Li, Y. Y.; He, N. N.; Guo, C. C.; J. Org. Chem. 2014, 79, 7372. (12) (a) Lu, Q.; Zhang, J.; Zhao, G.; Qi, Y.; Wang, H.; Lei, A.; J. Am. Chem. Soc. 2013, 135, 11481. (b) Handa, S.; Fennewald, J. C.; Lipshutz, B. H.; Angew. Chem. Int. Ed. 2014, 53, 3432. (13) For some selected examples, see: (a) Kapileswar, S.; Manesh, N.; Priyank, P.; Naisargee, P.; Asit, K. C.; Chem. Commun., 2015, 51, 191. (b) Basickes, N.; Hogan, T. E.; Sen, A.; J. Am. Chem. Soc. 1996, 118, 13111. (c) Lin, M.; Sen, A.; J. Chem. Soc. Chem. Commun. 1992, 892. (d) Minisci, F.; Citterio A.; Giordano, C.; Acc. Chem. Res. 1983, 16, 27.

(14) (a) Dickstein, J. S.; Mulrooney, C. A.; O’Brien, E. M.; Morgan, B. J.; Kozlowski, M. C.; Org. Lett., 2007, 9, 13. (b) Klahn, P.; Erhardt, H.; Kotthaus, A.; Kirsch, S. F.; Angew. Chem. Int. Ed. 2014, 53, 7913. (15) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.; Timmers, F. J.; Organometallics, 1996, 15, 1518.


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(16) (a) Sun, H.; Zhang, Y.; Guo, F.; Zha, Z.; Wang, Z.; J. Org. Chem. 2012, 77, 3563. (b) Cheng, K.; Huang, L.; Zhang, Y.; Org. Lett. 2009, 11, 2908. (c) Asano, K.; Matsubara, S.; J. Am. Chem. Soc., 2011, 133, 16711. (17) Li, Z.; Yu, R.; Li, H.; Angew. Chem. Int. Ed. 2008, 47, 7497.


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