Compound 35
(S)-benzyl (2-formyl-4-phenylbutyl)carbamate
From: Direct, enantioselective α-alkylation of aldehydes using simple olefins
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Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.
Prepared according to the general procedure outlined for compound 13 with aldehyde (0.32 mmol),2equiv. water (11.5 µL), 0.02 equiv. Ir(ppy)2(dtbbpy)PF6(5.9 mg), 0.25 equiv. α,α-bis[3,5-bistrifluoromethyl)phenyl]-2-pyrrolidinemethanol trimethylsilyl ether (47.8 mg), and 2 equiv. 1-butyl-3-methyl-1H-imidazol-3-ium tetrafluoroborate (120 µL) in dimethoxyethane (1.07 mL, 0.3M). Purified by flash chromatography (25% EtOAc/hexanes) after reduction to the corresponding alcohol to provide the title compound (60 mg, 60% yield, 90% ee) as a colorless oil. Analytical data: [α]D22+8.8 (c = 0.93, CHCl3); 1H NMR (500 MHz, CDCl3) δ 7.40–7.31 (m, 5H), 7.30–7.26 (m, 2H), 7.18 (dd, J = 10.1, 7.9 Hz, 3H), 5.11 (s, 2H), 5.02 (s, 1H), 3.65 (dd, J = 11.6, 3.0 Hz, 1H), 3.49 (dd, J = 11.6, 5.9 Hz, 1H), 3.38 (ddd, J = 14.3, 6.4, 3.6 Hz, 1H), 3.28–3.20 (m, 1H), 2.74–2.60 (m, 2H), 1.71–1.49 (m, 4H); 13C NMR (125 MHz, CDCl3) δ 157.9, 142.0, 136.4, 128.7, 128.6, 128.5, 128.4, 128.3, 126.1, 67.2, 62.6, 41.7, 40.9, 33.4, 30.4; HRMS (ESI+) Calcd. for C19H23NO3+H, 313.1678; Found, 313.1674; IR (thin film, cm-1) 3353, 3028, 2931, 1693, 1520, 1497, 1454, 1250, 1138, 1029, 980, 741; HPLC analysis of the alcohol (OJ, 20% IPA/Hexanes, 1.0 mL/min) indicates 90% ee: tR= 14.7 (major), 16.4 (minor) min.
