A mixture of (10c), (2.30.g, 6.94 mmol) and pyridinium dichromate (10.62 g, 28.2 mmol) in 20 mL of N,N-dimethylformamide is stirred under argon for 18 h. The reaction mixture is diluted with 100 mL of water and extracted with ethyl acetate (3×40 mL). The organic layer is separated, washed with water and brine, dried and evaporated to give 1.87 g of a residual brown liquid. The liquid is purified by chromatography using 1:6 ethyl acetate/hexane to give 997 mg of the desired product as an oil. NMR δ 0.83 (s, 9H), 1.61 (m, 2H), 2.22 (t, 2H), 2.23 (s, 3H), 3.82 (dd, 1H), 4.09 (dd, 1H), 4.57 (m, 1H), 6.42 (brd, 1H); MS (FAB) m/z 330 (M+H calc'd. for C17H36NO3Si 330).
