Regioselective and Stereospecific Cu-Catalyzed Deoxygenation of Epoxides to Alkenes

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1 Supporting Information Regioselective and Stereospecific Cu-Catalyzed Deoxygenation of Epoxides to Alkenes Jingxun Yu, Yu Zhou, Zhenyang Lin*, and Rongbiao Tong* Table of Contents General Information S-2 General Procedure for the Preparation of Epoxides from Alkenes S-2 Preparation of Diepoxides 1x, 1y, and 1z S-3 Standard Procedure for Cu-Catalyzed Deoxygenation of Epoxides to Alkenes S-5 Table S1. Copper-catalyzed Deoxygenation with other Diazo Compounds S-5 NMR data of Compounds 3a 3z, S-6 Computational Details S-13 Copies of 1 H- and 13 C NMR Spectra S-20 S1

2 General Information: Reactions were carried out in oven or flame-dried glassware under a nitrogen atmosphere, unless otherwise noted. Tetrahydrofuran (THF) was freshly distilled before use from sodium using benzophenone as indicator. Dichloromethane (DCM) was freshly distilled before use from calcium hydride (CaH 2 ). All other anhydrous solvents were dried over 3Å or 4Å molecular sieves. Solvents used in workup, extraction and column chromatography were used as received from commercial suppliers without prior purification. Reactions were magnetically stirred and monitored by thin layer chromatography (TLC, 0.25 mm) on Merck precoated silica gel plates. Flash chromatography was performed with silica gel 60 (particle size mm) supplied by Grace. Infrared spectra were collected on a Bruker model TENSOR27 spectrophotometer. 1 H and 13 C NMR spectra were recorded on a Bruker AV-400 spectrometer (400 MHz for 1 H, 100 MHz for 13 C). Chemical shifts are reported in parts per million (ppm) as values relative to the internal d 6 -chloroform (7.26 ppm for 1 H and ppm for 13 C). Abbreviations for signal coupling are as follows: s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet. High resolution mass spectra were measured at the Hong Kong University of Science and Technology Mass Spectrometry Service Center on an Agilent GC/MS 5975C System. Note: compounds 3b, 3m 3r, and 3u are commercially available. General Procedure for the Preparation of Epoxides from Alkenes: General Procedure A (epoxidation with m-cpba): To a stirred solution of alkene (5 mmol) in dichloromethane (20 ml) was added m-cpba (2.03 g, 10 mmol) at room temperature. The reaction mixture was stirred for 2 h and then the reaction was quenched by addition of saturated aqueous Na 2 SO 3 (10 ml). The organic layer was collected and the aqueous layer was extracted with CH 2 Cl 2 (3 x 20 ml). The combined organic fractions were washed with brine, dried over Na 2 SO 4, filtered and concentrated under reduced pressure. The crude product was purified by flash column chromatography on silica gel to afford the desired epoxide product. This procedure was used to prepare epoxides 1a 1i, 1m 1q and 1t 1w. General Procedure B (epoxidation with H 2 O 2 ): To a stirred solution of alkene in methanol were added dropwise H 2 O 2 (30 wt%,15 mmol, 1.5 ml) and NaOH (15 wt%, 0.45 ml) at 0 o C. After the reaction mixture was stirred for 3 h, Na 2 SO 3 (10 ml) was added to quench the reaction. The organic layer was collected and the aqueous layer was extracted with CH 2 Cl 2 (3 x 20 ml). The combined organic fractions were washed with brine, dried over Na 2 SO 4, filtered and concentrated under reduced pressure. The crude product was purified by flash column S2

3 chromatography on silica gel to afford the desired epoxide product. This procedure was used to prepare epoxides 1j 1l and 1r 1s. Preparation of Diepoxides 1x, 1y, and 1z Epoxide 1s 1 was prepared from (R)-carvone. To a stirred solution of 1s (5 mmol) in CH 2 Cl 2 (20 ml) was added m-cpba (2.03 g, 10 mmol) at r. The reaction mixture was stirred for 2 h and then the reaction was quenched by addition of saturated aqueous Na 2 SO 3 (10 ml). The organic layer was collected and the aqueous layer was extracted with CH 2 Cl 2 (3 x 20 ml). The combined organic fractions were washed with brine, dried over Na 2 SO 4, filtered and concentrated under reduced pressure. The crude product was purified by flash column chromatography on silica gel to afford the desired epoxide product 1x (0.91 g) with 82% yield. Epoxide 3aa 2 was prepared from geraniol. To a stirred solution of 3aa (1.06 g, 5 mmol) in THF (20 ml) and H 2 O (2 ml) were added 2 wt % of OsO 4 (0.5 ml) solution and NMO (0.88 g). The reaction was stirred at room temperature for 2 h. NaIO 4 (2.13 g, 10 mmol) was added and the reaction mixture was stirred for additional 2 h. The reaction was quenched by addition of saturated aqueous Na 2 S 2 O 3. The organic layer was collected and the aqueous layer was extracted with EtOAc (3 x 20 ml). The combined organic fractions were washed with brine, dried over Na 2 SO 4 and concentrated under reduced pressure. The crude product was purified by flash column chromatography on silica gel (hexane/etoac = 5:1) to afford the desire product S-1 3 (0.88 g) with 95% yield. 1 Weinstabl, H.; Gaich, T.; Mulzer, J. Org. Lett. 2012, 14, Ding, X.-B.; Furkert, D. P.; Capon, R. J.; Brimble, M. A. Org. Lett. 2014, 16, (a) Pettifrew, J. D.; Paquette, L. A. Heterocycles, 2010, 80, (b) Wagman, A. S.; Wang, L.; Nuss, J. M. J. Org. Chem. 2000, 65, S3

4 To a stirred solution of the ethyl sulfone tetrazole (476 mg, 2.0 mmol) in THF (10 ml) was added slowly t-buok (1.2 mmol, 1.2 ml, 1 M in THF) under -78 o C. The reaction mixture was stirred for 1 h and then S-1 (186 mg, 1.0 mmol) in THF (2 ml) was added dropwise into the reaction mixture over 30 min. After the reaction mixture was stirred under -78 o C for additional 2 h, the reaction was quenched by addition of saturated aqueous NH 4 Cl (1 ml). The organic layer was collected and the aqueous layer was extracted with CH 2 Cl 2 (3 x 2 ml). The combined organic fractions were washed with brine, dried over Na 2 SO 4, filtered and concentrated under reduced pressure. The crude product was purified by flash column chromatography on silica gel (hexane/etoac = 10:1) to afford the desired product 3y (182 mg) with 92 % yield. Epoxidation of 3y was performed with m-cpba using the General Procedure A to provide the diepoxide 1y in 85% yield. 1y: light yellow oil. 1 H NMR (400 MHz, CDCl 3 ) δ: (m, 1 H), 4.28 (dd, J = 12.1, 4.4 Hz, 1 H), 3.16 (dd, J = 7.1, 1.9 Hz, 1 H), (m, 1 H), 2.96 (dd, J = 5.2, 2.0 Hz, 1 H), (m, 5 H), (m, 2 H), (m, 3 H), 1.32 (m, 3 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 168.0, 69.1, 66.4, 63.5, 60.2, 59.7, 38.7, 28.7, 21.5, 18.4, The preparation of the diepoxide 1z 4 (172 mg, 76% yield) was performed using the same procedure for the synthesis of 1y. 1z: light yellow oil. 1 H NMR (400 MHz, CDCl 3 ) δ: (m, 1 H), 4.24 (dd, J = 12.1, 4.4 Hz, 1 H), (m, 2 H), (m, 1 H), (m, 1 H), (m, 2 H), 2.05 (s, 3 H), (m, 2 H), 1.35 (s, 3 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 165.9, 70.1, 66.2, 62.5, 60.1, 59.7, 38.7, 28.7, 18.6, Ye, Y.; Zheng, C.; Fan, R. Org. Lett. 2009, 11, S4

5 Standard Procedure for Cu-Catalyzed Deoxygenation of Epoxides to Alkenes: Deoxygenation with DAM (diazo malonate): To a solution of epoxide (0.2 mmol) in anhydrous toluene (1 ml) was added 5 mol% catalyst (IMesCuCl or Cu(TFA) 2 ). The reaction mixture was heated at reflux and DAM (0.3 mmol) was added very slowly over 2 h via syringe pump and then reaction vessel was sealed (without exclusion of air) and stirred at reflux for additional 2 h. The reaction was quenched by addition of saturated aqueous NH 4 Cl (1 ml) and extracted with CH 2 Cl 2 (3 x 2 ml). The combined organic fractions were washed with brine, dried over Na 2 SO 4, filtered and concentrated under reduced pressure. The crude product was purified by flash column chromatography on silica gel (hexane/etoac = 10:1 to 3:1) to afford the desired alkene. Note: IMes = 1,3-bis(mesity)-imidazol-2-ylidene. Table S1. Copper-catalyzed deoxygenation of 1a with other diazo compounds that have been examined Entry Diazo Comp. Cat. (5 mol%) Conv.(%) Yield(%) 1 b IMesCuCl < b Cu(TFA) 2 < IMesCuCl Cu(TFA) IMesCuCl Cu(TFA) IMesCuCl 0-8 Cu(TFA) IMesCuCl Cu(TFA) IMesCuCl S5

6 12 Cu(TFA) IMesCuCl Cu(TFA) IMesCuCl Cu(TFA) a: 5 yellow oil, 75% (with IMesCuCl, 28.8 mg), 81% (with Cu(TFA) 2, 31.1 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: (m, 2 H), (m, 2 H), 5.84 (ddt, J = 17.0, 10.2, 6.7 Hz, 1 H), (m, 2 H), 4.46 (s, 2 H), 3.81 (s, 3 H), 3.50 (t, J = 6.8 Hz, 2H), 2.37 (qt, J = 6.8, 1.4 Hz, 2 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 159.2, 135.3, 130.6, 129.3, 116.3, 113.8, 72.6, 69.3, 55.3, b: colorless oil, 85% (with IMesCuCl, 35.7 mg) and 80% (with Cu(TFA) 2, 33.6 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: (m, 1 H), (m, 2 H), (m, 2 H), (m, 21 H), (m, 4 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 139.3, 114.1, 33.9, 31.9, 29.6, 29.5, 29.4, 29.2, 29.0, 22.7, c: 6 colorless oil, 95% (with IMesCuCl, 19.8 mg) and 93% (with Cu(TFA) 2, 19.2 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: (m, 2 H), (m, 2 H), (m, 1 H), 6.74 (dd, J = 17.6, 10.8 Hz, 1 H), 5.77 (d, J = 17.6 Hz, 1 H), 5.26 (d, J = 10.9 Hz, 1 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 137.5, 136.9, 128.5, 127.8, 126.2, Yu, Z.; Eno, M. S.; Annis, A. H.; Morken, J. P. Org. Lett. 2015, 17, Mitsudome, T.; Noujima, A.; Mikami, Y.; Mizugaki, T.; Jitsukawa, K.; Kaneda, K. Angew. Chem. Int. Ed. 2010, 49, S6

7 3d: 6 colorless oil, 83% (with IMesCuCl, 19.4 mg) and 88% (with Cu(TFA) 2, 20.8 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: (m, 4 H), (m, 1 H), 6.42 (dd, J = 15.8, 1.5 Hz, 1 H), 6.26 (dq, J = 15.8, 6.6 Hz, 1 H), 1.90 (dd, J = 6.5, 1.6 Hz, 3 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 137.9, 131.0, 128.4, 126.7, 125.8, 125.7, e: 6 white powder, 78% (with IMesCuCl, 19.8 mg) and 70% (with Cu(TFA) 2, 15.8 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: (m, 4 H), 7.37 (t, J = 7.7 Hz, 2 H), (m, 1 H), 7.13 (s, 2 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 137.3, 128.7, 128.7, 127.6, f: 6 white powder, 75% (with IMesCuCl, 27.0 mg) and 72% (with Cu(TFA) 2, 25.8 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: (m, 10 H), 6.67 (d, J = 1.68 Hz, 2 H). 13 C NMR (101 MHz, CDCl 3 ) δ: 137.2, 130.2, 128.8, 128.2, g: 7 colorless oil, 76% (with IMesCuCl, 40.7 mg) and 74% (with Cu(TFA) 2, 39.6 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: 7.40 (s, 8 H), (m, 2 H), 5.84 (t, J = 3.7, 1.8 Hz, 2 H), 4.53 (s, 4 H), 4.11 (d, J = 4.2 Hz, 4 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 138.1, 129.4, 128.3, 127.7, 127.6, 72.2, h: 7 colorless oil, 82% (with IMesCuCl, 54.1 mg) and 85% (with Cu(TFA) 2, 56.8 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: (m, 5 H), (m, 1 H), 5.74 (dd, J = 6.4, 4.9 Hz, 1 H), 4.52 (d, J = 5.0 Hz, 2 H), (m, 2 H), (m, 2 H), (m, 21 H). 7 Kour, H.; Paul, S.; Singh, P.P.; Gupta, M.; Gupta, R. Tetrahedron. Lett. 2013, 54, S7

8 13 C NMR (100 MHz, CDCl 3 ) δ: 133.2, 132.8, 128.4, 128.3, 127.8, 127.7, 127.6, 127.5, 72.2, 71.9, 59.8, 18.0, 18.0, 17.7, 12.3, 12.0, i: colorless oil, 85% (with IMesCuCl, 18.4 mg) and 82% (with Cu(TFA) 2, 17.7 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: 5.59 (s, 4 H), 2.37 (s, 8 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 128.7, j: colorless oil, 82% (with IMesCuCl, 15.7 mg) and 86% (with Cu(TFA) 2, 16.9 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: 6.95 (dt, J = 10.1, 4.1 Hz, 1 H), 5.96 (dt, J = 10.1, 2.1 Hz, 1 H), (m, 2 H), (m, 2 H), (m, 2 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 199.6, 150.6, 129.8, 38.0, 25.5, k: 8 colorless oil, 92% (with IMesCuCl, 18.1 mg) and 84% (with Cu(TFA) 2, 12.3 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: 7.70 (d, J = 16.0 Hz, 1 H), (m, 2 H), (m, 3 H), 6.45 (d, J = 16.0 Hz, 1 H), 3.81 (s, 3 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 167.4, 144.9, 134.4, 130.3, 128.9, 128.1, 117.8, l: 9 white solid, 67% (with IMesCuCl, 41.9 mg) and 72% (with Cu(TFA) 2, 44.9 mg). 8 Liu, J.-B.; Chen, F.-J.; Liu, N.; Hu, J. RSC Advances, 2015, 57, Song, L.; Liu, Y.; Tong, R. Org. Lett. 2013, 15, S8

9 1 H NMR (400 MHz, CDCl 3 ) δ: 6.08 (d, J = 11.8 Hz, 1 H), 5.64 (dd, J = 11.8, 8.9 Hz, 1 H), (m, 1 H), (m, 1 H), 2.76 (dd, J = 14.9, 5.7 Hz, 1 H), 2.43 (ddd, J = 13.3, 9.8, 3.0 Hz, 1 H), (m, 3 H), (m, 1 H), (m, 1 H), 1.23 (d, J = 6.3 Hz, 3 H), 0.88 (s, 9 H), 0.14 (s, 3 H), 0.11 (s, 3 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 204.5, 169.1, 139.4, 131.4, 71.4, 64.8, 44.5, 38.7, 32.2, 25.7, 19.1, 18.0, -4.6, m: colorless oil, 72% (with IMesCuCl, 18.2 mg) and 72% (with Cu(TFA) 2, 20.1 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: (m, 1 H), (m, 2 H), 5.76 (d, J = 15.3 Hz, 1 H), 4.19 (q, J = 7.1 Hz, 2 H), 1.84 (d, J = 5.8 Hz, 3 H), 1.28 (t, J = 7.1 Hz, 3 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 167.3, 144.9, 139.2, 129.8, 119.0, 60.1, 18.6, n: colorless oil, 80% (with IMesCuCl, 18.8 mg) and 92% (with Cu(TFA) 2, 21.4 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: 7.53 (dd, J = 7.7, 2.3 Hz, 2 H), 7.39 (td, J = 8.0, 7.6, 2.1 Hz, 2 H), 7.32 (dt, J = 8.1, 3.8 Hz, 1 H), 5.43 (s, 1 H), 5.15 (s, 1 H), 2.22 (s, 3 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 143.3, 141.2, 128.2, 127.4, 125.5, 112.4, o: white solid, 88% (with IMesCuCl, 31.6 mg) and 74% (with Cu(TFA) 2, 27.7 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: (m, 10 H), 5.48 (s, 2 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 150.0, 141.5, 128.3, 128.1, 127.7, p: colorless oil, 64% (with IMesCuCl, 13.6 mg) and 48% (with Cu(TFA) 2, 7.7 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: 4.80 (s, 1 H), 4.62 (s, 1 H), (m, 1 H), (m, 1 H), (m, 2 H), 1.59 (d, J = 5.8 Hz, 1 H), (m, 1 H), 0.95 (d, J = 6.8 Hz, 3 H), 0.88 (d, J = 6.9 Hz, 3 H), (m, 2 H). S9

10 13 C NMR (100 MHz, CDCl 3 ) δ: 154.5, 101.5, 37.6, 32.6, 30.1, 29.0, 27.5, 19.8, 19.7, q: colorless oil, 65% (with IMesCuCl, 7.6 mg) and 46% (with Cu(TFA) 2, 5.7 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: 5.55 (dq, J = 4.7, 1.6 Hz, 1 H), (m, 1 H), (m, 1 H), (m, 5 H), 1.09 (s, 3 H), 0.95 (dd, J = 8.8, 4.4 Hz, 1 H), (m, 4 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 133.6, 119.5, 28.5, 27.4, 24.0, 23.8, 22.9, 21.0, 17.8, r: light yellow oil, 88% (with IMesCuCl, 18.2 mg) and 84% (with Cu(TFA) 2, 18.8 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: 6.73 (d, J = 5.7 Hz, 1 H), (m, 1 H), (m, 1 H), (m, 2 H), (m, 4 H), (m, 1 H), 0.88 (dd, J = 6.7, 1.5 Hz, 6 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 200.7, 145.3, 135.3, 42.0, 42.0, 32.0, 29.9, 19.5, 19.5, s: 5 colorless oil, 84% (with IMesCuCl, 11.1 mg) and 74% (with Cu(TFA) 2, 8.4 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: (m, 1 H), 4.75 (s, 1 H), 4.70 (s, 1 H), 2.63 (ddd, J = 14.4, 10.3, 4.4 Hz, 1 H), 2.52 (ddd, J = 16.0, 3.7, 1.5 Hz, 1 H), 2.40 (dt, J = 18.3, 5.4 Hz, 1 H), (m, 2 H), 1.73 (s, 3 H), 1.70 (s, 3 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 199.6, 146.6, 144.5, 135.4, 110.4, 43.1, 42.4, 31.2, 20.5, t: colorless oil, 84% (with IMesCuCl, 31.7 mg) and 80% (with Cu(TFA) 2, 30.2 mg). S10

11 1 H NMR (400 MHz, CDCl 3 ) δ: 5.44 (d, J = 5.2 Hz, 1 H), 3.87 (dd, J = 10.1, 2.7 Hz, 1 H), 3.65 (dd, J = 10.1, 6.7 Hz, 1 H), (m, 1 H), (s, 1 H), 1.78 (s, 3 H), (m, 2 H), (m, 25 H), 0.88 (s, 3 H), 0.86 (s, 3 H), 0.77 (s, 2 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 134.7, 122.4, 62.1, 57.4, 49.9, 42.2, 39.7, 35.9, 33.3, 33.0, 23.7, 22.4, 22.0, 18.9, 18.2, 17.7, 14.4, HRMS (TOF, CI ) m/z calc. for C 24 H 46 OSi, [M+H] , found u: white powder, 85% (with IMesCuCl, 36.3 mg) and 83% (with Cu(TFA) 2, 33.0 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: (m, 1 H), (m, 1 H), (m, 1 H), (m, 2 H), (m, 2 H), 2.03 (s, 3 H), (m, 4 H), (m, 6 H), (m, 2 H), (m, 1 H), (s, 4 H), 0.88 (s, 3 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 170.5, 139.9, 121.9, 73.7, 51.7, 50.1, 47.5, 38.1, 36.9, 36.7, 35.8, 31.5, 31.4, 30.8, 27.7, 21.9, 21.4, 20.3, 19.3, s: colorless oil, 85% (IMesCuCl, 28.2 mg) and 80% (Cu(TFA) 2, 26.6 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: 4.77 (s, 1 H), 4.70 (s, 1 H), 3.43 (dd, J = 3.1, 1.2 Hz, 1 H), 2.70 (ddd, J = 15.9, 11.2, 4.6 Hz, 1 H), 2.57 (ddd, J = 17.6, 4.7, 1.4 Hz, 1 H), 2.35 (ddd, J = 14.7, 5.2, 2.3 Hz, 1 H), 2.01 (dd, J = 17.6, 11.6 Hz, 1 H), 1.88 (ddd, J = 14.8, 11.1, 1.2, 1 H), (m, 3 H), 1.39 (s, 3 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 205.5, 146.3, 110.5, 61.3, 58.8, 41.8, 35.0, 28.7, 20.6, y: light yellow oil, 86% (with IMesCuCl, 34.1 mg) and 77% (with Cu(TFA) 2, 30.5 mg). S11

12 1 H NMR (400 MHz, CDCl 3 ) δ: (m, 2 H), 4.34 (dt, J = 12.1, 4.4 Hz, 1 H), 4.05 (ddd, J = 12.1, 7.0, 4.2 Hz, 1H), (m, 1 H), (m, 5 H), (m, 2 H), 1.45 (d, J = 1.2 Hz, 3 H), 1.32 (s, 3 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 165.9, 133.0, 125.6, 63.4, 60.5, 59.7, 38.2, 28.1, 20.8, 17.9, HRMS (TOF, CI ) m/z calc. for C 11 H 18 O 3, [M+H] , found z: colorless oil, 93% (with IMesCuCl, 34.2 mg) and 91% (with Cu(TFA) 2, 33.2 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: 5.79 (ddt, J = 16.8, 10.3, 6.5 Hz, 1 H), (m, 2H), (m, 1 H), 4.03 (ddd, J = 12.1, 6.9, 1.2 Hz, 1 H), (m, 1 H), (m, 2 H), 2.07 (s, 3 H), (m, 2 H), 1.32 (s, 3 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 164.3, 137.6, 115.1, 63.4, 60.0, 59.7, 37.5, 29.3, 20.8, HRMS (TOF, CI ) m/z calc. for C 10 H 16 O 3, [M+H] , found aa: 10 yellow oil, 27.5% (with IMesCuCl, 11.6 mg). 1 H NMR (400 MHz, CDCl 3 ) δ: (m, 1 H), 4.31 (ddd, J = 12.2, 4.4, 1.8 Hz, 1 H), 4.02 (ddt, J = 12.3, 7.0, 1.7 Hz, 1 H), (m, 2 H), 2.10 (s, 3 H), (m, 2 H), 1.68 (d, J = 2.1 Hz, 3 H), 1.60 (d, J = 2.6 Hz, 3 H), 1.47 (tdd, J = 9.5, 7.3, 3.7 Hz, 1 H), 1.31 (s, 3 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 170.9, 132.2, 123.2, 63.4, 60.6, 59.7, 38.3, 25.7, 23.6, 20.8, 17.6, aa : 10 light yellow oil, 11.5% (with IMesCuCl, 4.87 mg). 10 (a) Smith, B. M.; Skellam, E. J.; Oxley, S. J.; Graham, A. E. Org. Biomol. Chem. 2007, 5, (b) Oliver, J. E.; Dickens, J. C.; Glass, T. E. Tetrahedron Lett. 2002, 43, S12

13 1 H NMR (400 MHz, CDCl 3 ) δ: (m, 1 H), 4.56 (d, J = 7.2 Hz, 2 H), (m, 2 H), (m, 2 H), 2.04 (s, 3 H), (m, 1 H), 1.70 (s, 3 H), 1.09 (s, 3 H), 1.08 (s, 3 H). 13 C NMR (100 MHz, CDCl 3 ) δ: 170.6, 131.8, 128.6, 63.8, 58.5, 56.5, 38.7, 25.7, 23.9, 20.9, 17.5, Computational Details: All the calculations were performed with the Gaussian 09 program. 11 Geometry optimization was carried out using the DFT M06 functional. 12 In the DFT calculations, the 6-31G basis set was used for the methyl groups of the NHC ligand, while 6-311G* was employed for Cu, the Lanl2dz basis set 13 with polarization functions (ζ d =0.640) for Cl, and 6-31G* for the remaining C, H, O and N atoms. The IEFPCM model 14 was employed to stimulate the solvent effect, and all the structures were optimized considering the solvation effect. Frequencies were calculated to make sure that all the intermediates had no imaginary frequency and the transition state contained only one imaginary frequency. Intrinsic reaction coordinates (IRC) 15 were performed to ensure that a transition state did connect two 11 (1) 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, Jr., J. A.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; 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.; Daniels, A. D.; Farkas, Ö.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09, Revision D.01; Gaussian, Inc.: Wallingford, CT, Zhao, Y.; Truhlar, D. Theor. Chem. Acc. 2008, 120, (a) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 299; (b) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, Mennucci, B.; Cancès, E.; Tomasi, J. J. Phys. Chem. B 1997, 101, (a) Fukui, K. Acc. Chem. Res. 1981, 14, 363; (b) Fukui, K. J. Phys. Chem. 1970, 74, S13

14 relevant local minima. For simplicity, the IMes ligand was replaced by IMe ligand. Figure S1. Energy profiles calculated for different pathways leading to deoxygenation of epoxide. The relative free energies and electronic energies in parenthesis are given in kcal/mol. Cartesian coordinates and electronic energies for the calculated structures. Energies in Hartree Catalyst SCF Done: Cu C N N C C H H C H H H C H H H Cl Diazo compound SCF Done: S14 C C O O C O O C H H H C H H H N N TS SCF Done: Cu C N

15 N C C H H C H H H C H H H Cl O O O O N N C C C C C H H H H H H Cu carbene SCF Done: Cu C N N C C H H C H H H C H H H Cl O O O O C C C C C H H H H H H S15 Nitrogen gas SCF Done: N N Epoxide SCF Done: C C O H H H C H H H A SCF Done: Cu C N N C C H H C H H H C H H H Cl O O O O C C C C C H H H H H H C C O H H H C H H H TS AC

16 SCF Done: Cu C N N C C H H C H H H C H H H Cl O O O O C C C C C H H H H H H C C O H H H C H H H C SCF Done: Cu C N N C C H H C H H H C H H H Cl C C O O S16 C O O C H H H C H H H C C O H H H C H H H TS CD SCF Done: Cu C N N C C H H C H H H C H H H Cl C C O O C O O C H H H C H H H C C O H H H C H H H

17 D SCF Done: Cu C N N C C H H C H H H C H H H Cl C C O O C O O C H H H C H H H C C O H H H C H H H TS DF SCF Done: Cu C N N C C H H C H H H C H H H Cl C C O S17 O C O O C H H H C H H H C C O H H H C H H H TS CF SCF Done: Cu C N N C C H H C H H H C H H H Cl C C O O C O O C H H H C H H H C C O H H H C H H H

18 TS AB SCF Done: Cu C N N C C H H C H H H C H H H Cl C C O O C O O C H H H C H H H C C O H H H C H H H B SCF Done: Cu C N N C C H H C H H H C H H H Cl C S18 C O O C O O C H H H C H H H C C O H H H C H H H TS BF SCF Done: Cu C N N C C H H C H H O C O O C H H H C H H H O H C H H H Cl C C O O C O O C H

19 H H C H H H C C O H H H C H H H F SCF Done: C C H H H C H H H Dimethyl 2-oxomalonate SCF Done: C C O S19

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