A Strained Disilane-Promoted Carboxylation of Organic Halides with CO2 under Transition-Metal-Free Conditions

Transcription

1 A Strained Disilane-Promoted Carboxylation of Organic Halides with CO2 under Transition-Metal-Free Conditions Tsuyoshi Mita,* a Kenta Suga, a Kaori Sato, a and Yoshihiro Sato* ab a Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo , Japan b ACT-C, Japan Science and Technology Agency (JST), Sapporo , Japan tmita@pharm.hokudai.ac.jp biyo@pharm.hokudai.ac.jp Supporting Information S1

2 Table of Contents (A) General S3 (B) Synthesis of Substrates S3 (C) Carboxylation of Aryl Halides S4 (D) Carboxylation of Benzyl, Allyl, and Alkyl Halides S10 (E) Reaction with Benzaldehyde S13 (F) Copies of 1 H NMR and 13 C NMR S14 S2

3 (A) General All manipulations were carried out under argon atmosphere unless noted. Infrared (IR) spectra were recorded on a JASCO FT/IR 460 Plus Fourier transform infrared spectrophotometer. NMR spectra were recorded on a JEOL ECA-500 spectrometer, operating at 500 MHz ( 1 H) or 125 MHz ( 13 C). Chemical shifts in each solvents were reported in the scale relative to the following values as internal references; CDCl3: CHCl3 (7.26 ppm) for 1 H NMR, CDCl3 (77.0 ppm) for 13 C NMR; C6D6: C6H6 (7.16 ppm) for 1 H NMR, C6D6 ( ppm) for 13 C NMR; CD3OD: CH3OH (3.31 ppm) for 1 H NMR, CD3OD (49.0 ppm) for 13 C NMR; d6-dmso: DMSO (2.50 ppm) for 1 H NMR, d6-dmso (39.52 ppm) for 13 C NMR. ESI and APCI mass spectra were measured on Thermo Scientific Exactive. Column chromatography was performed with silica gel Kanto 60 ( mesh ASTM). Dry DMF was purified under argon using the Ultimate Solvent System (Glass Counter Inc.). CsF was purchased from Nacalai Tesque. Inc. A cylinder of CO2 was purchased from Hokkaido Air Water, Inc. Caution! CH2N2 is potentially explosive. (B) Synthesis of Substrates 3,4-Benzo-1,1,2,2-tetraethyldisilacyclobutene was prepared from 1,2-dibromobenzene and chlorodiethylsilane 1 according to the reported method. 2 3,4-Benzo-1,1,2,2-tetraethyldisilacyclobutene: Colorless oil; IR (neat): 2952, 2871, 1458, 1415, 1375, 1257, 1231, 1088, 1004, 695 cm -1 ; 1 H NMR (500 MHz, CDCl3) = (m, 2H), (m, 2H), (m, 12H), (m, 8H) ppm; 13 C NMR (125 MHz, CDCl3) = 155.7, 132.2, 128.8, 8.8, 5.6 ppm. 1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h, 1i, 1j, 1k, 1l, 1m, 1o, 1p, 1q, 1r, 1s, 1t, 1u, 1v, 1w, 1x, 1y, 1ff, 1hh, 4-bromoanisole, 1-bromo-4-chlorobenzene, and 1,4-diiodobenzene were commercially available. 1-Iodo-4-vinylbenzene (1n), 3 2-iodo-1H-indene (1z), 4 1-((E)-2-iodovinyl)-4-methoxybenzene (1aa), 5 1 Kunai, A.; Kawakami, T.; Toyoda, E.; Ishikawa, M. Organometallics 1992, 11, Ishikawa, M.; Sakamoto, H.; Tabuchi, T. Organometallics 1991, 10, Thiebes, C.; Prakash, G. K. S.; Petasis, N. A.; Olah, G. A. Synlett 1998, 141. S3

4 (E)-1-iodohept-1-ene (1bb), 6 1-iodohept-1-yne (1cc), 7 1-(2-iodoethynyl)benzene (1dd), 8 benzyl iodide (1ee), 9 1-(3-iodoprop-1-en-2-yl)benzene (1gg), 10 1-(4-iodobutyl)benzene (1ii), 11 6-iodohex-1-ene (1jj), 12 and (4-iodobutoxy)(tert-butyl)diphenylsilane (1kk) 13 were prepared by the reported methods. (C) Carboxylation of Aryl Halides CsF (91.1 mg, 0.6 mmol, 3 equiv) was placed to a 15 ml test tube and dried for 5 min by a heat gun under vacuum before use (<5 mmhg at ca. 400 o C), then the test tube was filled with CO2 gas (1 atm: balloon). When a substrate 1 is a solid, 1 was added before the addition of dry DMF. When 1 is liquid, DMF solution of 1 was added to the reaction tube. The resultant mixture was vigorously stirred at 0 o C, and 3,4-benzo-1,1,2,2-tetraethyldisilacyclobutene (99.4 mg, 108 L, 0.4 mmol, 2 equiv) was added in one portion. The mixture was warmed to room temperature and stirred for 2 h. After monitoring the reaction progress by TLC, H2O (10 ml) and 1 M HCl aq. (3 ml) were added to the mixture and extracted with AcOEt (10 ml x3). The combined organic layer was washed with brine and dried over Na2SO4. The solvent was removed under reduced pressure to afford the crude product. The yield was determined at this stage using 1,1,2,2-tetrachloroethane ( = 5.9 ppm in CDCl3, 2H) as an internal standard. The crude product was then purified by silica-gel column chromatography to afford carboxylic acid 2. If the property of 2 was not suitable for the isolation by silica-gel column chromatography due to its solubility and/or polarity, the crude 2 was converted to the methyl ester 3 by methyl esterification reagent. 4-Methoxybenzoic acid (2a): 1a (46.8 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 15:1) to afford 2a (30.2 mg, mol, 99% yield). 4-bromoanisole (37.4 mg, 0.2 mmol) was used as a substrate. The yield of 2a was determined by using 1,1,2,2-tetrachloroethane ( = 5.9 ppm in CDCl3, 2H) as an internal standard (35% yield). White solid; IR (nujol): 2925, 2853, 1685, 1603, 1427, 1261, 1167, 1026, 846, 773 cm -1 ; 1 H NMR (500 MHz, CDCl3) = 8.07 (d, J = 8.9, 2H), 6.95 (d, J = 8.9 Hz, 2H), 3.88 (s, 3H) ppm; 13 C NMR (125 MHz, CDCl3) = 171.6, 164.0, 132.4, 121.6, 113.7, 55.5 ppm. Aldrich product No Methoxybenzoic acid (2b): 1b (46.8 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 10:1) to afford 2b (27.3 mg, mol, 90% yield). White solid; IR (nujol): 2925, 2853, 1693, 1584, 1465, 1431, 1311, 1291, 1045, 755 cm -1 ; 1 H NMR (500 MHz, CDCl3) = (bs, 1H), 7.73 (d, J = 7.7 Hz, 1H), (m, 1H), 7.39 (dd, J = 8.4, 7.7 Hz, 1H), 7.17 (dd, J = 8.4, 2.4 Hz, 1H), 3.87 (s, 3H) ppm; 13 C NMR (125 MHz, CDCl3) = 172.2, 159.6, 130.5, 4 Hapke, M.; Kral, K.; Spannenberg, A. Synthesis 2011, Chowdhury, S.; Roy, S. J. Org. Chem. 1997, 62, Shakhmaev, R. N.; Ishbaeva, A. U.; Sunagatullina, A. S.; Zorin, V. V. Rus. J. Gen. Chem. 2011, 81, Gao, Y.; Yin, M.; Wu, W.; Huang, H.; Jiang, H. Adv. Synth. Catal. 2013, 355, Hashmi, A. S. K.; Döpp, R.; Lothschütz, C.; Rudolph, M.; Riedel, D.; Rominger, F. Adv. Synth. Catal. 2010, 352, Hoang, C. T.; Alezra, V.; Guillot, R.; Kouklovsky, C. Org. Lett. 2007, 9, Yemets, S. V.; Shubina, T. E.; Krasutsky, P. A. Org. Biomol. Chem. 2013, 11, Smith, S. M.; Takacs, J. M. J. Am. Chem. Soc. 2010, 132, Baldwin, J. E.; Bischoff, L.; Claridge, T. D. W.; Heupel, F. A.; Spring, D. R.; Whitehead, R. C. Tetrahedron 1997, 53, Ott, M. M.; Little, R. D. J. Org. Chem. 1997, 62, S4

5 129.5, 122.7, 120.5, 114.3, 55.4 ppm. Aldrich product No Methoxybenzoic acid (2c): 1c (46.8 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 15:1) to afford 2c (25.6 mg, mol, 84% yield). White solid; IR (nujol): 2924, 2853, 1694, 1669, 1599, 1464, 1377, 1315, 1261, 762 cm -1 ; 1 H NMR (500 MHz, CDCl3) = (bs, 1H), 8.17 (dd, J = 8.0, 1.7 Hz, 1H), 7.57 (dd, J = 8.0, 7.4 Hz, 1H), 7.13 (dd, J = 8.0, 7.4 Hz, 1H), 7.06 (d, J = 8.0 Hz, 1H), 4.07 (s, 3H) ppm; 13 C NMR (125 MHz, CDCl3) = 165.5, 158.0, 135.1, 133.7, 122.1, 117.5, 111.6, 56.6 ppm. Aldrich product No Methyl 4-ethoxybenzoate (3d) 14 : 1d (49.6 mg, 0.2 mmol) was used as a substrate. The crude product was dissolved in Et2O (2 ml) and treated with excess CH2N2 in Et2O and stirred for 10 min. The solvent was evaporated and the residue was purified by silica-gel column chromatography (hexane/etoac, 7:1) to afford 3d (33.2 mg, mol, 92% yield). White oil; IR (nujol): 2925, 2854, 1724, 1606, 1460, 1438, 1280, 1254, 1168, 1110 cm -1 ; 1 H NMR (500 MHz, CDCl3) = 7.98 (d, J = 9.2 Hz, 2H), 6.89 (d, J = 9.2 Hz, 2H), 4.08 (q, J = 6.9 Hz, 2H), 3.88 (s, 3H), 1.43 (t, J = 6.9 Hz, 3H) ppm; 13 C NMR (125 MHz, CDCl3) = 166.9, 162.7, 131.6, 122.4, 114.0, 63.6, 51.8, 14.7 ppm. Methyl 3,4,5-trimethoxybenzoate (3e): 1e (58.8 mg, 0.2 mmol) was used as a substrate. The crude product was dissolved in Et2O (2 ml) and treated with excess CH2N2 in Et2O and stirred for 10 min. The solvent was evaporated and the residue was purified by silica-gel column chromatography (hexane/etoac, 8:1) to afford 3e (37.6 mg, mol, 83% yield). White solid; IR (nujol): 2925, 2853, 1718, 1591, 1464, 1414, 1377, 1337, 1228, 1132 cm -1 ; 1 H NMR (500 MHz, C6D6) = 7.47 (s, 2H), 3.78 (s, 3H), 3.58 (s, 3H), 3.33 (s, 6H) ppm; 13 C NMR (125 MHz, C6D6) = 166.6, 153.9, 143.5, 125.6, 107.6, 60.5, 55.7, 51.7 ppm. Aldrich product No. M Hydroxybenzoic acid (2f): 1f (44.0 mg, 0.2 mmol) was used as a substrate. Disilane (3 equiv) was employed. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 10:1) to afford 2f (19.2 mg, mol, 70% yield). White solid; IR (nujol): 3379, 2924, 2853, 1674, 1604, 1462, 1366, 1246, 1171, 1014 cm -1 ; 1 H NMR (500 MHz, CD3OD) = 7.88 (d, J = 8.9 Hz, 2H), 6.82 (d, J = 8.9 Hz, 2H) ppm; 13 C NMR (125 MHz, CD3OD) = 170.1, 163.4, 133.0, 122.7, ppm. Aldrich product No Methylbenzoic acid (2g): 1g (43.6 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 15:1) to afford 2g (24.6 mg, mol, 90% yield). White solid; IR (nujol): 2925, 2854, 1673, 14 Node, M.; Nishide, K.; Sai, M.; Fuji, K.; Fujita, E. J. Org. Chem. 1981, 46, S5

6 1610, 1463, 1417, 1377, 1284, 1182, 755 cm -1 ; 1 H NMR (500 MHz, CDCl3) = 8.02 (d, J = 8.3 Hz, 2H), 7.28 (d, J = 8.3 Hz, 2H), 2.44 (s, 3H) ppm; 13 C NMR (125 MHz, CDCl3) = 172.6, 144.6, 130.2, 129.2, 126.6, 21.7 ppm. Aldrich product No. T Butylbenzoic acid (2h): 1h (52.0 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 15:1) to afford 2h (34.2 mg, mol, 96% yield). White solid; IR (nujol): 2925, 2854, 1693, 1610, 1465, 1426, 1377, 1319, 1290, 1179 cm -1 ; 1 H NMR (500 MHz, CDCl3) = 8.04 (d, J = 8.0 Hz, 2H), 7.29 (d, J = 8.0 Hz, 2H), 2.69 (t, J = 7.7 Hz 2H), (m, 2H), (m, 2H), 0.94 (t, J = 7.4 Hz, 3H) ppm; 13 C NMR (125 MHz, CDCl3) = 172.6, 149.5, 130.3, 128.5, 126.8, 35.8, 33.2, 22.3, 13.9 ppm. Aldrich product No ,5-Dimethylbenzoic acid (2i): 1i (46.2 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 15:1) to afford 2i (26.2 mg, mol, 87% yield). White solid; IR (nujol): 2924, 2854, 1687, 1607, 1457, 1377, 1314, 1246, 935, 726 cm -1 ; 1 H NMR (500 MHz, CDCl3) = 7.74 (s, 2H), 7.25 (s, 1H), 2.38 (s, 6H) ppm; 13 C NMR (125 MHz, CDCl3) = 172.7, 138.2, 135.5, 129.1, 127.9, 21.1 ppm. Aldrich product No. D Benzoic acid (2j): 1j (40.8 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (hexane/etoac, 4:1) to afford 2j (22.0 mg, mol, 90% yield).white solid; IR (nujol): 2925, 2853, 1692, 1455, 1377, 1326, 1291, 1179, 935, 709 cm -1 ; 1 H NMR (500 MHz, CDCl3) = 8.11 (dd, J = 8.3, 1.1 Hz, 2H), 7.62 (t, J = 7.4 Hz, 1H), 7.48 (dd, J = 8.3, 7.4 Hz, 2H) ppm; 13 C NMR (125 MHz, CDCl3) = 172.4, 133.8, 130.2, 129.3, ppm. Aldrich product No Naphthoic acid (2k): 1k (50.8 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 15:1) to afford 2k (29.9 mg, mol, 87% yield). White solid; IR (nujol): 2925, 2854, 1673, 1592, 1513, 1462, 1377, 1301, 1251, 773 cm -1 ; 1 H NMR (500 MHz, CDCl3) = 9.11 (d, J = 8.6 Hz, 1H), 8.43 (dd, J = 7.4, 1.1 Hz, 1H), 8.11 (d, J = 8.6 Hz, 1H), 7.93 (d, J = 8.6 Hz, 1H), (m, 1H), (m, 2H) ppm; 13 C NMR (125 MHz, CDCl3) = 173.1, 134.7, 134.0, 131.9, 131.6, 128.7, 128.1, 126.3, 125.9, 125.6, ppm. Aldrich product No. N Naphthoic acid (2l): 1l (50.8 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 15:1) to afford 2l (31.0 mg, mol, 90% yield). White solid; IR (nujol): 2925, 2854, 1682, 1464, 1376, 1306, 1240, 1201, 1047, 781 cm -1 ; 1 H NMR (500 MHz, CDCl3) = 8.74 (s, 1H), 8.14 (dd, J = 8.6, 1.7 Hz, 1H), 8.00 (d, J = 8.0 Hz, 1H), (m, 2H), (m, 2H) ppm; 13 C NMR (125 MHz, CDCl3) = 172.4, 135.9, 132.4, 132.2, 129.6, 128.7, 128.3, 127.8, 126.8, 126.5, ppm. Aldrich product No S6

7 Methyl 4-phenylbenzoate (3m): 1m (56.0 mg, 0.2 mmol) was used as a substrate. Disilane (3 equiv) was employed. The crude product was dissolved in Et2O (2 ml) and treated with excess CH2N2 in Et2O and stirred for 10 min. The solvent was evaporated and the residue was purified by silica-gel column chromatography (hexane/etoac, 7:1) to afford 3m (38.9 mg, mol, 92% yield). White solid; IR (nujol): 2925, 2854, 1718, 1457, 1439, 1377, 1289, 1270, 1115, 751 cm -1 ; 1 H NMR (500 MHz, CDCl3) = 8.11 (d, J = 8.5 Hz, 2H), 7.67 (d, J = 8.5 Hz, 2H), 7.63 (d, J = 7.7 Hz, 2H), 7.47 (dd, J = 7.7, 7.3 Hz, 2H), 7.40 (t, J = 7.3 Hz, 1H), 3.95 (s, 3H) ppm; 13 C NMR (125 MHz, CDCl3) = 167.0, 145.6, 140.0, 130.1, , , 128.1, 127.3, 127.0, 52.1 ppm. Aldrich product No. P Vinylbenzoic acid (2n): 1n (46.0 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 15:1) to afford 2n (25.8 mg, mol, 87% yield). White solid; IR (nujol): 2925, 2854, 1678, 1604, 1464, 1419, 1319, 1290, 1180, 924 cm -1 ; 1 H NMR (500 MHz, CDCl3) = (bs, 1H), 8.09 (d, J = 8.0 Hz, 2H), 7.50 (d, J = 8.0 Hz, 2H), 6.78 (dd, J = 17.8, 10.9 Hz, 1H), 5.90 (d, J = 17.8 Hz, 1H), 5.42 (d, J = 10.9 Hz, 1H) ppm; 13 C NMR (125 MHz, CDCl3) = 172.2, 142.8, 135.9, 130.5, 128.4, 126.2, ppm. Aldrich product No Chlorobenzoic acid (2o): 1o (47.7 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 15:1) to afford 2o (28.2 mg, mol, 90% yield). 1-bromo-4-chlorobenzene (38.3 mg, 0.2 mmol) was used as a substrate. 4-bromoanisole (37.4 mg, 0.2 mmol) was used as a substrate. The yield of 2o was determined by using 1,1,2,2-tetrachloroethane ( = 5.9 ppm in CDCl3, 2H) as an internal standard (71% yield). White solid; IR (nujol): 2925, 2853, 1682, 1592, 1463, 1425, 1373, 1321, 1283, 1092 cm -1 ; 1 H NMR (500 MHz, CD3OD) = 8.00 (d, J = 8.6 Hz, 2H), 7.49 (d, J = 8.6 Hz, 2H) ppm; 13 C NMR (125 MHz, CD3OD) = 168.7, 140.2, 132.3, 130.7, ppm. Aldrich product No Chlorobenzoic acid (2p): 1p (47.7 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 15:1) to afford 2p (24.8 mg, mol, 79% yield). White solid; IR (nujol): 2924, 2854, 1689, 1592, 1463, 1410, 1377, 1316, 1268, 745 cm -1 ; 1 H NMR (500 MHz, CDCl3) = 8.04 (d, J = 8.0 Hz, 1H), (m, 2H), (m, 1H) ppm; 13 C NMR (125 MHz, CDCl3) = 170.9, 134.8, 133.6, 132.5, 131.5, 128.4, ppm. Aldrich product No Trifluoromethylbenzoic acid (2q): 1q (54.4 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 10:1) to afford 2q (33.5 mg, mol, 88% yield). White solid; IR (nujol): 2924, 2853, 1697, 1462, 1376, 1318, 1289, 1170, 1144, 1063 cm -1 ; 1 H NMR (500 MHz, CD3OD) = 8.19 (d, J = 7.5 Hz, 2H), 7.78 (d, J = 7.5 Hz, 2H) ppm; 13 C NMR (125 MHz, CD3OD) = 168.0, 136.2, (q, J = 32 Hz), 131.4, (q, J = 4 Hz), (q, J = 271 Hz) S7

8 ppm. Aldrich product No (35.8 mg, mol, 92% yield). Dimethyl terephthalate (3r): 1r (52.4 mg, 0.2 mmol) was used as a substrate. The crude product was dissolved in Et2O (2 ml) and treated with excess CH2N2 in Et2O and stirred for 10 min. The solvent was evaporated and the residue was purified by silica-gel column chromatography (hexane/etoac, 6:1) to afford 3r 1,4-diiodobenezne (66.0 mg, 0.2 mmol) was used as a substrate. Disilane (4 equiv) and CsF (6 equiv) were employed. The crude product was dissolved in Et2O (2 ml) and treated with excess CH2N2 in Et2O and stirred for 10 min. The solvent was evaporated and the residue was purified by silica-gel column chromatography (hexane/etoac, 6:1) to afford 3r (26.4 mg, mol, 68% yield). White solid; IR (nujol): 2925, 2854, 1719, 1448, 1434, 1408, 1280, 1193, 1108, 734 cm -1 ; 1 H NMR (500 MHz, CDCl3) = 8.08 (s, 4H), 3.93 (s, 6H) ppm; 13 C NMR (125 MHz, CDCl3) = 166.2, 133.8, 129.5, 52.4 ppm. Aldrich product No Acetylbenzoic acid (2s): 1s (49.2 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 15:1) to afford 2s (24.9 mg, mol, 76% yield). Yellow solid; IR (nujol): 2925, 2854, 1681, 1506, 1463, 1430, 1377, 1291, 935, 772 cm -1 ; 1 H NMR (500 MHz, d6-dmso) = (s, 4H), 2.63 (s, 3H) ppm; 13 C NMR (125 MHz, d6-dmso) = 197.8, 166.7, 139.9, 134.5, 129.6, 128.4, 27.0 ppm. Aldrich product No Nitrobenzoic acid (2t): 1t (49.8 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (EtOAc/MeOH, 9:1) to afford 2t (30.8 mg, mol, 92% yield). Yellow solid; IR (nujol): 2925, 2854, 1694, 1605, 1523, 1462, 1346, 1312, 1295, 719 cm -1 ; 1 H NMR (500 MHz, d6-dmso) = 8.32 (d, J = 8.6 Hz, 2H), 8.16 (d, J = 8.6 Hz, 2H) ppm; 13 C NMR (125 MHz, d6-dmso) = 165.8, 150.0, 136.6, 130.7, ppm. Aldrich product No Methyl ferrocenecarboxylate (3u): 1u (52.9 mg, 0.2 mmol) was used as a substrate. Disilane (3 equiv) was employed. The crude product was dissolved in Et2O (2 ml) and treated with excess CH2N2 in Et2O and stirred for 10 min. The solvent was evaporated and the residue was purified by silica-gel column chromatography (hexane/etoac, 8:1) to afford 3u (25.0 mg, mol, 51% yield). Yellow solid; IR (nujol): 2925, 2854, 1725, 1712, 1701, 1464, 1376, 1281, 1190, 1140 cm -1 ; 1 H NMR (500 MHz, CDCl3) = (m, 2H), (m, 2H), 4.20 (s, 5H), 3.80 (s, 3H) ppm; 13 C NMR (125 MHz, CDCl3) = 172.2, 71.2, 71.0, 70.1, 69.7, 51.6 ppm. Aldrich product No. S Thiophene-2-carboxylic acid (2v): 1v (42.0 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (hexane/etoac, 3:1) to afford 2v (22.4 mg, mol, 88% yield). White solid; IR (nujol): 3097, 2924, 2854, S8

9 1686, 1530, 1459, 1436, 1286, 737, 723 cm -1 ; 1 H NMR (500 MHz, CDCl3) = (bs, 1H), 7.91 (dd, J = 3.9, 1.3 Hz, 1H), 7.66 (dd, J = 4.9, 1.3 Hz, 1H), 7.15 (dd, J = 4.9, 3.9 Hz, 1H) ppm; 13 C NMR (125 MHz, CDCl3) = 167.8, 135.0, 134.0, 132.9, ppm. Aldrich product No. T Thiophene-3-carboxylic acid (2w): 1w (42.0 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 15:1) to afford 2w (22.6 mg, mol, 85% yield). White solid; IR (nujol): 3106, 2924, 2854, 1686, 1523, 1459, 1377, 1279, 1111, 748 cm -1 ; 1 H NMR (500 MHz, CDCl3) = 8.25 (dd, J = 3.1, 1.1 Hz, 1H), 7.58 (dd, J = 5.2, 1.1 Hz, 1H), 7.34 (dd, J = 5.2, 3.1 Hz, 1H) ppm; 13 C NMR (125 MHz, CDCl3) = 168.1, 134.6, 132.8, 128.1, ppm. Aldrich product No Methyl nicotinate (3x): 1x (41.0 mg, 0.2 mmol) was used as a substrate. After the reaction, Cs2CO3 (130.3 mg, 0.4 mmol, 2 equiv) and MeI (34.1 mg, 15 L, 0.24 mmol, 1.2 equiv) were added to the reaction mixture and stirred for 1 h at room temperature. After monitoring the reaction progress by TLC, H2O (10 ml) was added and extracted by AcOEt (10 ml x3). The combined organic layer was washed with brine and dried over Na2SO4. The solvent was evaporated and the residue was purified by silica-gel column chromatography (hexane/etoac, 4:1) to afford 3x (21.9 mg, mol, 80% yield). White solid; IR (nujol): 2925, 2854, 1736, 1590, 1456, 1425, 1285, 1117, 741, 703 cm -1 ; 1 H NMR (500 MHz, CDCl3) = 9.22 (s, 1H), 8.77 (dd, J = 4.4, 1.7 Hz, 1H), (m, 1H), (m, 1H), 3.96 (s, 3H) ppm; 13 C NMR (125 MHz, CDCl3) = 165.8, 153.4, 150.9, 137.0, 126.0, 123.3, 52.4 ppm. Aldrich product No. M Methyl 1H-indole-5-carboxylate (3y): 1y (48.6 mg, 0.2 mmol) was used as a substrate. Disilane (3 equiv) was employed. The crude product was dissolved in Et2O (2 ml) and treated with excess CH2N2 in Et2O and stirred for 10 min. The solvent was evaporated and the residue was purified by silica-gel column chromatography (hexane/etoac, 4:1) to afford 3y (15.7 mg, 89.6 mol, 45% yield). White solid; IR (nujol): 3332, 2925, 2854, 1698, 1614, 1459, 1435, 1294, 1271, 1199 cm -1 ; 1 H NMR (500 MHz, CDCl3) = (m, 2H), 7.91 (dd, J = 8.6, 1.7 Hz, 1H), 7.41 (d, J = 8.6 Hz, 1H), (m, 1H), (m, 1H), 3.94 (s, 3H) ppm; 13 C NMR (125 MHz, CDCl3) = 168.2, 138.4, 127.4, 125.5, 123.8, 123.4, 121.9, 110.7, 104.0, 51.9 ppm. Aldrich product No H-Indene-2-carboxylic acid (2z) 15 : 1z (48.4 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 10:1) to afford 2z (29.8 mg, mol, 93% yield). White solid; IR (nujol): 2925, 2854, 1662, 1591, 1567, 1463, 1378, 1353, 1273, 758 cm -1 ; 1 H NMR (500 MHz, CDCl3) = 7.88 (s, 1H), (m, 2H), (m, 2H), 3.73 (s, 2H) ppm; 13 C NMR (125 MHz, CDCl3) = 169.4, 145.2, 143.6, 142.5, 136.2, 128.1, 127.0, 124.4, 123.7, 38.1 ppm. 15 Fujihara, T.; Nogi, K.; Xu, T.; Terao, J.; Tsuji, Y. J. Am. Chem. Soc. 2012, 134, S9

10 (E)-Methyl 3-(4-methoxyphenyl)acrylate (3aa) 16 : 1aa (33.2 mg, 0.2 mmol) was used as a substrate. The crude product was dissolved in Et2O (2 ml) and treated with excess CH2N2 in Et2O and stirred for 10 min. The solvent was evaporated and the residue was purified by silica-gel column chromatography (hexane/etoac, 8:1) to afford 3aa (33.2 mg, mol, 86% yield). White solid; IR (nujol): 2925, 2853, 1716, 1637, 1604, 1514, 1463, 1288, 1206, 1171 cm -1 ; 1 H NMR (500 MHz, CDCl3) = 7.65 (d, J = 16.0 Hz, 1H), 7.47 (d, J = 9.3 Hz, 2H), 6.90 (d, J = 9.3 Hz, 2H), 6.31 (d, J = 16.0 Hz, 1H), 3.84 (s, 3H), 3.79 (s, 3H) ppm; 13 C NMR (125 MHz, CDCl3) = 167.8, 161.4, 144.5, 129.7, 127.1, 115.2, 114.3, 55.4, 51.6 ppm. (E)-Oct-2-enoic acid (2bb): 1bb (44.8 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 15:1) to afford 2bb (13.6 mg, 95.6 mol, 48% yield). Colorless oil; IR (neat): 2958, 2931, 2860, 1697, 1651, 1420, 1284, 1235, 987, 936 cm -1 ; 1 H NMR (500 MHz, CDCl3) = 7.09 (dt, J = 15.6, 7.0 Hz, 1H), 5.82 (d, J = 15.6 Hz, 1H), (m, 2H), (m, 2H), (m, 4H), 0.89 (t, J = 7.0 Hz, 3H) ppm; 13 C NMR (125 MHz, CDCl3) = 172.0, 152.5, 120.5, 32.3, 31.3, 27.5, 22.4, 13.9 ppm. Aldrich product No. O5209. Oct-2-ynoic acid (2cc): 1cc (44.4 mg, 0.2 mmol) was used as a substrate. Disilane (3 equiv) was employed. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 15:1) to afford 2cc (24.0 mg, mol, 86% yield). Colorless oil; IR (neat): 2959, 2934, 2864, 2238, 1687, 1411, 1281, 1077, 756, 727 cm -1 ; 1 H NMR (500 MHz, CDCl3) = (bs, 1H), 2.35 (t, J = 7.2 Hz, 2H), (m, 2H), (m, 4H), 0.90 (t, J = 7.2 Hz, 3H) ppm; 13 C NMR (125 MHz, CDCl3) = 158.5, 92.9, 72.6, 30.9, 27.0, 22.1, 18.7, 13.8 ppm; HRMS (APCI): m/z calcd for C8H12O2 [M-H] + : , Found: Methyl 3-phenylpropiolate (3dd): 1dd (45.6 mg, 0.2 mmol) was used as a substrate. Disilane (3 equiv) was employed. The crude product was dissolved in Et2O (2 ml) and treated with excess CH2N2 in Et2O and stirred for 10 min. The solvent was evaporated and the residue was purified by silica-gel column chromatography (hexane/ch2cl2, 3:1) to afford 3dd (26.2 mg, mol, 82% yield). Colorless oil; IR (neat): 3060, 2953, 2226, 1714, 1490, 1435, 1289, 1203, 1172, 758 cm -1 ; 1 H NMR (500 MHz, CDCl3) = 7.58 (d, J = 7.5 Hz, 2H), 7.45 (t, J = 7.4 Hz, 1H), 7.37 (dd, J = 7.5, 7.4 Hz, 2H), 3.84 (s, 3H) ppm; 13 C NMR (125 MHz, CDCl3) = 154.4, 133.0, 130.7, 128.6, 119.5, 86.5, 80.3, 52.8 ppm. Aldrich product No (D) Carboxylation of Benzyl, Allyl, and Alkyl Halides CsF (91.1 mg, 0.6 mmol, 3 equiv) was placed to a 15 ml test tube and dried for 5 min by a heat gun under vacuum before use (<5 mmhg at ca. 400 o C), then the test tube was filled with CO2 gas (1 atm: balloon). DMF solution of 1 was added to the reaction tube. The resultant mixture was vigorously stirred 16 Youn, S. W.; Kim, B. S.; Jagdale, A. R. J. Am. Chem. Soc, 2012, 134, S10

11 at 0 o C, and 3,4-benzo-1,1,2,2-tetraethyldisilacyclobutene (99.4 mg, 108 L, 0.4 mmol, 2 equiv) was added in one portion. The mixture was warmed to room temperature and stirred for 2 h. After monitoring the reaction progress by TLC, H2O (10 ml) and 1 M HCl aq. (3 ml) were added to the mixture and extracted with AcOEt (10 ml x3). The combined organic layer was washed with brine and dried over Na2SO4. The solvent was removed under reduced pressure to afford the crude product. The yield was determined at this stage using 1,1,2,2-tetrachloroethane ( = 5.9 ppm in CDCl3, 2H) as an internal standard. The crude product was then purified by silica-gel column chromatography to afford carboxylic acid 2 and/or ester 4. 2-Phenylacetic acid (2ee) 17 : 1ee (43.6 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 10:1) to afford 2ee (10.0 mg, 73.4 mol, 37% yield). White solid; IR (nujol): 2925, 2854, 1699, 1456, 1408, 1377, 1229, 927, 752, 701 cm -1 ; 1 H NMR (500 MHz, CDCl3) = (m, 2H), (m, 3H), 3.66 (s, 2H) ppm; 13 C NMR (125 MHz, CDCl3) = 177.5, 133.2, 129.4, 128.6, 127.3, 41.0 ppm. Benzyl 2-phenylacetate (4ee): 1ee (43.6 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 10:1) to afford 4ee (4.5 mg, 19.9 mol, 20% yield). Colorless oil; IR (neat): 3064, 3032, 2927, 1736, 1496, 1455, 1258, 1146, 724, 696 cm -1 ; 1 H NMR (500 MHz, CDCl3) = (m, 10H), 5.14 (s, 2H), 3.68 (s, 2H) ppm; 13 C NMR (125 MHz, CDCl3) = 171.4, 135.8, 133.9, 129.3, 128.6, 128.5, 128.2, 128.1, 127.1, 66.6, 41.3 ppm. Aldrich product No. W Butenoic acid (2ff): 1ff (33.6 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 15:1) to afford 2ff (5.8 mg, 67.4 mol, 34% yield). However, this compound was volatile and hard to separate from DMF. Colorless oil; IR (neat): 2931, 1719, 1647, 1415, 1387, 1256, 1188, 1104, 994, 924 cm -1 ; 1 H NMR (500 MHz, CDCl3) = (m, 1H), (m, 1H), (m, 1H), 3.14 (d, J = 6.9 Hz, 2H) ppm; 13 C NMR (125 MHz, CDCl3) = 176.7, 129.7, 119.0, 38.7 ppm. Aldrich product No Phenylbut-3-enoic acid (2gg) 18 : 1gg (48.8 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 10:1) to afford 2gg (9.8 mg, 60.4 mol, 30% yield). Yellow solid; IR (nujol): 2924, 2854, 1713, 1462, 1377, 1304, 1236, 908, 782, 698 cm -1 ; 1 H NMR (500 MHz, CDCl3) (m, 2H), (m, 3H), 5.59 (s, 1H), 5.26 (s, 1H), 3.55 (s, 2H) ppm; 13 C NMR (125 MHz, CDCl3) = 177.4, 140.1, 139.4, 128.5, 127.9, 125.7, 116.8, 40.8 ppm. 17 Korsager, S.; Taaning, R. H.; Skrydstrup, T. J. Am. Chem. Soc. 2013, 135, Miao, B.; Ma, S. Chem. Commun. 2014, 50, S11

12 2-Phenylprop-2-en-1-yl 3-phenyl-3-butenoate (4gg) 19 : 1g (48.8 mg, 0.2 mmol) was used as a substrate. The yield of 4gg was determined by using 1,1,2,2-tetrachloroethane ( = 5.9 ppm in CDCl3, 2H) as an internal standard (15% yield). White solid; IR (neat): 3056, 2932, 1739, 1630, 1263, 1247, 1151, 898, 776, 703 cm -1 ; 1 H NMR (500 MHz, CDCl3) = (m, 10H), 5.53 (s, 1H), 5.49 (s, 1H), 5.26 (s, 1H), 5.22 (s, 1H), 4.96 (s, 2H), 3.54 (s, 2H) ppm; 13 C NMR (125 MHz, CDCl3) = 171.0, 142.3, 140.6, 139.6, 138.0, , , 128.0, 127.8, 126.0, 125.8, 116.4, 115.4, 66.1, 41.2 ppm. Hexyl heptanoate (4hh): 1hh (42.4 mg, 0.2 mmol) was used as a substrate. The yield of 4hh was determined by using 1,1,2,2-tetrachloroethane ( = 5.9 ppm in CDCl3, 2H) as an internal standard (42% yield). Colorless oil; IR (neat): 2957, 2930, 2859, 1739, 1467, 1379, 1258, 1236, 1171, 1103 cm -1 ; 1 H NMR (500 MHz, CDCl3) = 4.06 (t, J = 6.9 Hz, 2H), 2.29 (t, J = 7.7 Hz, 2H), (m, 4H), (m, 12H), (m, 6H) ppm; 13 C NMR (125 MHz, CDCl3) = 174.0, 64.4, 34.4, 31.45, 31.43, 28.8, 28.6, 25.6, 25.0, 22.53, 22.48, 14.01, ppm; HRMS (APCI): m/z calcd for C13H26O2 [M+H] + : , Found: Phenylbutyl 5-phenylpentanoate (4ii): 1ii (52.0 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (hexane/etoac, 15:1) to afford 4ii (16.4 mg, 52.9 mol, 53% yield). Colorless oil; IR (neat): 3026, 2937, 2859, 1733, 1604, 1496, 1454, 1174, 747, 699 cm -1 ; 1 H NMR (500 MHz, CDCl3) = (m, 4H), (m, 6H), 4.17 (t, J = 6.3 Hz, 2H), (m, 4H), 2.40 (t, J = 7.2 Hz, 2H), (m, 8H) ppm; 13 C NMR (125 MHz, CDCl3) = 173.7, 142.1, 142.0, 128.4, , , 125.8, 125.7, 64.1, 35.5, 35.4, 34.2, 30.9, 28.2, 27.7, 24.6 ppm; HRMS (APCI): m/z calcd for C21H26O2 [M+H] + : , Found: Hex-5-enyl hept-6-enoate (4jj): 1jj (42.0 mg, 0.2 mmol) was used as a substrate. The crude mixture was purified by silica-gel column chromatography (CH2Cl2/MeOH, 15:1) to afford 4jj (10.4 mg, 49.4 mol, 49% yield). Yellow oil; IR (neat): 3078, 2935, 2861, 1737, 1641, 1457, 1417, 1171, 994, 912 cm -1 ; 1 H NMR (500 MHz, CDCl3) = (m, 2H), (m, 4H), 4.07 (t, J = 6.9 Hz, 2H), (m, 2H), (m, 4H), (m, 4H), (m, 4H) ppm; 13 C NMR (125 MHz, CDCl3) = 173.8, , , 114.8, 114.7, 64.2, 34.2, 33.4, 33.3, 28.3, 28.1, 25.2, 24.4 ppm; HRMS (APCI): m/z calcd for C13H22O2 [M+H] + : , Found: (tert-Butyldiphenylsiloxy)butyl 5-(tert-butyldiphenylsiloxy)pentanoate (4kk): 1kk (87.7 mg, 0.2 mmol) was used as a substrate. The crude mixture 19 Kiyokawa, K.; Yahata, S.; Kojima, T.; Minakata, S. Org. Lett. 2014, 16, S12

13 was purified by silica-gel column chromatography (hexane/etoac, 20:1) to afford 4kk (27.0 mg, 40.4 mol, 40% yield). Colorless oil; IR (neat): 3071, 2955, 2931, 2858, 1736, 1472, 1428, 1167, 1111, 702 cm -1 ; 1 H NMR (500 MHz, CDCl3) = (m, 8H), (m, 12H), 4.07 (t, J = 6.6 Hz, 2H), (m, 4H), 2.29 (t, J = 7.4 Hz, 2H), (m, 4H), (m, 4H), (s, 9H), (s, 9H) ppm; 13 C NMR (125 MHz, CDCl3) = 173.7, 135.5, , , , , , , 64.2, 63.4, 63.3, 34.0, 31.9, 29.0, 26.8, 25.2, 21.4, 19.2 ppm; HRMS (ESI): m/z calcd for C41H54O4Si2 [M+Na] + : , Found: The crude product contained compound V, which was purified by silica-gel column chromatography. 1,1,3,3-Tetraethyl-1,3-dihydrobenzo[c][1,2,5]oxadisilole (V) 2 : Colorless oil; IR (neat): 3048, 2956, 2876, 1460, 1411, 1235, 1113, 1007, 919, 734 cm -1 ; 1 H NMR (500 MHz, CDCl3) = (m, 2H), (m, 2H), (m, 12H), (m, 8H) ppm; 13 C NMR (125 MHz, CDCl3) = 146.8, 131.6, 128.7, 7.3, 6.6 ppm; MS (APCI): m/z calcd for C14H24OSi2 [M+H] + : , Found: (E) Reaction with Benzaldehyde CsF (91.1 mg, 0.6 mmol, 3 equiv) was placed to a 15 ml test tube and dried for 5 min by a heat gun under vacuum before use (<5 mmhg at ca. 400 o C), then the test tube was filled with argon. To the reaction tube were added 1a (46.8 mg, 0.2 mmol, 1 equiv), dry DMF (1.4 ml), and benzaldehyde (21.2 mg, 20.4 L, 0.2 mmol, 1 equiv). The resultant mixture was vigorously stirred at 0 o C, and 3,4-benzo-1,1,2,2-tetraethyldisilacyclobutene (99.4 mg, 108 L, 0.4 mmol, 2 equiv) was added in one portion. The mixture was warmed to room temperature and stirred for 2 h. H2O (10 ml) was added to the mixture and extracted with AcOEt (10 ml x3). The combined organic layer was washed with brine and dried over Na2SO4. The solvent was removed under reduced pressure to afford the crude product. The yield of 5 and anisaldehyde were determined using 1,1,2,2-tetrachloroethane ( = 5.9 ppm in CDCl3, 2H) as an internal standard (22% and 10% yield, respectively). 1,1,4,4-Tetraethyl-3,4-dihydro-3-phenyl-1H-benzo[c][1,2,5]oxadisiline (5) 2 : Colorless oil; IR (neat): 2955, 2875, 1459, 1414, 1234, 1119, 1042, 1026, 830, 700 cm -1 ; 1 H NMR (500 MHz, CDCl3) = (m, 8H), (m, 1H), 5.20 (s, 1H), (m, 20H) ppm; 13 C NMR (125 MHz, CDCl3) = 143.7, 143.4, 141.8, 134.0, 132.8, , , 128.1, 125.4, 124.4, 67.9, 7.5, 7.3, 7.1, 6.8, 6.7, 6.5, 2.6, 1.8 ppm; MS (APCI): m/z calcd for C21H30OSi2 [M+H] + : , Found: When benzaldehyde was used as an electrophile, 3,4-benzo-1,1,2,2-tetraethyldisilacyclobutene was prefer to react with benzaldehyde rather than 1a, affording the six-membered ring product 5. An inert character of this disilane over CO2 resulted in the selective activation of halocarbons to generate reactive carbanions under a CO2 atmosphere. S13

14 500 MHz, CDCl SiEt 2 SiEt 2 S

15 125 MHz, CDCl SiEt 2 SiEt 2 S

16 500 MHz, CDCl CO 2 H MeO 2a S

17 125 MHz, CDCl CO 2 H MeO 2a S

18 500 MHz, CDCl MeO CO 2 H 2b S

19 125 MHz, CDCl MeO CO 2 H 2b S

20 500 MHz, CDCl OMe CO 2 H 2c S

21 125 MHz, CDCl OMe CO 2 H 2c S

22 500 MHz, CDCl CO 2 Me EtO 3d S

23 125 MHz, CDCl CO 2 Me EtO 3d S

24 500 MHz, C6D MeO CO 2 Me MeO OMe 3e S

25 125 MHz, C6D MeO CO 2 Me MeO OMe 3e S

26 500 MHz, CD3OD CO 2 H HO 2f S

27 125 MHz, CD3OD CO 2 H HO 2f S

28 500 MHz, CDCl CO 2 H 2g S

29 125 MHz, CDCl CO 2 H 2g S

30 500 MHz, CDCl CO 2 H Bu 2h S

31 125 MHz, CDCl CO 2 H Bu 2h S

32 500 MHz, CDCl CO 2 H 2i S

33 125 MHz, CDCl CO 2 H 2i S

34 500 MHz, CDCl CO 2 H 2j S

35 125 MHz, CDCl CO 2 H 2j S

36 500 MHz, CDCl CO 2 H 2k S

37 125 MHz, CDCl CO 2 H 2k S

38 500 MHz, CDCl CO 2 H 2l S

39 125 MHz, CDCl CO 2 H 2l S

40 500 MHz, CDCl CO 2 Me Ph 3m S

41 125 MHz, CDCl CO 2 Me Ph 3m S

42 500 MHz, CDCl CO 2 H 2n S

43 125 MHz, CDCl CO 2 H 2n S

44 500 MHz, CD3OD CO 2 H Cl 2o S

45 125 MHz, CD3OD CO 2 H Cl 2o S

46 500 MHz, CDCl CO 2 H 2p Cl S

47 125 MHz, CDCl CO 2 H 2p Cl S

48 500 MHz, CD3OD CO 2 H F 3 C 2q S

49 S49 2q F 3 C CO 2 H MHz, CD3OD

50 500 MHz, CDCl CO 2 Me MeO 2 C 3r S

51 125 MHz, CDCl CO 2 Me MeO 2 C 3r S

52 500 MHz, d6-dmso CO 2 H Ac 2s S

53 125 MHz, d6-dmso CO 2 H Ac 2s S

54 500 MHz, d6-dmso CO 2 H O 2 N 2t S

55 125 MHz, d6-dmso CO 2 H O 2 N 2t S

56 500 MHz, CDCl Fe CO 2 Me 3u S

57 125 MHz, CDCl Fe CO 2 Me 3u S

58 500 MHz, CDCl S 2v CO 2 H S

59 125 MHz, CDCl S 2v CO 2 H S

60 500 MHz, CDCl CO 2 H S 2w S

61 125 MHz, CDCl CO 2 H S 2w S

62 500 MHz, CDCl CO 2 Me N 3x S

63 125 MHz, CDCl CO 2 Me N 3x S

64 500 MHz, CDCl CO 2 Me N H 3y S

65 125 MHz, CDCl CO 2 Me N H 3y S

66 500 MHz, CDCl CO 2 H 2z S

67 125 MHz, CDCl CO 2 H 2z S

68 500 MHz, CDCl CO 2 Me MeO 3aa S

69 125 MHz, CDCl CO 2 Me MeO 3aa S