Lithium amide → (3S,alphaR)-t-Butyl 3-(N-allyl-alpha-methylbenzylamino)-4-pentenoate

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Reaction Steps

A solution of (R)-N-allyl-α-methylbenzylamine (24) (1.78 g, 11.1 mmol) in anhydrous tetrahydrofuran (20 ml) was cooled to -78° C. and 1.6M butyllithium (6.00 ml, 9.5 mmol) was added dropwise via a syringe. The resulting orange lithium amide solution was stirred at -78° C. for 1 hour. A solution of t-butyl pentadienoate (25) (1.137 g, 7.4 mmol) in anhydrous tetrahydrofuran (15 ml) was then added via a cannula and the solution was stirred for a further 1 hour. The reaction was quenched by the addition of saturated aqueous ammonium chloride solution and the solution was allowed to warm to room temperature. Ethyl acetate (50 ml) was added, followed by brine (10 ml). The organic layer was separated, dried (magnesium sulphate) and filtered and the solvent evaporated under reduced pressure to afford a pale yellow oil. This was purified by flash chromatography on silica gel [ethyl acetate/petroleum ether (1:49)] to afford the title compound (Rf 0.25) as a colourless oil (1.97 g, 85%). δH (300 MHz; CDCl3) 7.40-7.19 (5H, m, Ph), 5.94-5.74 (2H, m, CH2 =CHCH and NCH2CH=CH2), 5.16-5.00 (4H, m, CH2 =CHCH and NCH2CH=CH2), 4.02 (1H, q, J=6.8, PhCHCH3), 3.90 (1H, app. q, J=7.1, NCHCH2), 3.15 (2H, d, J=6.1, NCH2CH=CH2), 2.41 (1H, dd, J=6.4 and 14.5, CH2CO2), 2.31 (1H, dd, J=14.5 and 8.3, CH2CO2), 1.42 (9H, s, (CH3)3C), 1.39 (3H, d, J=6.8, PhCHCH3).

Provenance & Evidence