Compound 39
(R)-2-(2-(1-benzyl-1H-pyrazol-4-yl)ethyl)octanal
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. Purified by flash chromatography (10% Et2O/hexanes) using Davisil to provide the title compound (134 mg, 86% yield, 92% ee) as a colorless oil. Analytical data: [α]D22+4.9 (c = 0.50, CHCl3); 1H NMR (500 MHz, CDCl3) δ 9.56 (d, J = 2.9 Hz, 1H), 7.37 (s, 1H), 7.34 (ddd, J = 7.3, 4.5, 1.5 Hz, 2H), 7.30 (ddd, J = 7.4, 3.5, 1.4 Hz, 1H), 7.23–7.19 (m, 2H), 7.17 (s, 1H), 5.26 (s, 2H), 2.52–2.38 (m, 2H), 2.27 (dqd, J = 10.9, 5.4, 2.9 Hz, 1H), 1.94–1.84 (m, 1H), 1.70– 1.60 (m, 2H), 1.51–1.43 (m, 1H), 1.26 (s, 8H), 0.87 (t, J = 6.9 Hz, 3H); 13C NMR (125 MHz, CDCl3) δ 205.3, 138.9, 136.8, 128.9, 128.2, 127.8, 127.8, 121.3, 56.1, 51.4, 31.7, 30.1, 29.5, 29.0, 27.1, 22.7, 21.9, 14.2; HRMS (ESI+) Calcd. for C20H28ON2+H, 312.2202; Found, 312.2203; IR (thin film, cm-1) 2926, 2856, 1721, 1455, 1396, 1156, 994, 726, 702; HPLC analysis of the corresponding alcohol (AS, 5% IPA/Hexanes, 1.0 mL/min) indicates 92% ee: tR= 15.7 (major), 17.7 (minor) min.
