反应详情

Following the general procedure for methylenation via Wittig-olefination of Description 8, a phosphorous ylide generated from 17.86 g (50.0 mmol) of methyltriphenylphosphonium bromide and 31.0 mmol of n-BuLi in 125 mL of anhydrous tetrahydrofuran (THF), was reacted with 5.5 g (25.0 mmol) of (4R)-5,5-dimethyl-2-phenyl-1,3-dioxan-4-carbaldehyde (7b). Aqueous work-up followed by purification using column chromatography with mixtures of methyl tert-butyl ether (MTBE) and hexanes (Hxn) as eluent (MTBE/Hxn=9:1→MTBE/Hxn=6:1) provided 4.67 g (86% yield) of the title compound (7c) as a yellowish liquid. Rf=0.66 (MTBE/Hxn=1:6). 1H NMR (400 MHz, CHCl3): δ=0.82 (s, 3H), 1.16 (s, 3H), 3.67 (d, J=10.8 Hz, 1H), 3.78 (d, J=10.8 Hz, 1H), 4.05 (d, J=6.0 Hz, 1H), 5.24-528 (m, 1H), 5.31-5.37 (m, 1H), 5.55 (s, 1H), 5.87 (ddd, J=17.6, 10.4, 6.0 Hz, 1H), 7.30-7.40 (m, 3H), 7.52-7.55 (m, 2H) ppm. MS (ESI) m/z: 219.1 (M+H)+. The analytical data was consistent with that given in the literature (Ito, et al., Synthesis 1993, 137-140).

1. customAqueous work-up followed by purification