A solution of 2-(benzhydrylidene-amino)-hex-5-enoic acid tert-butyl ester (350 mg, 1 mmol) in THF (5 mL, 0.2 M) was cooled to −78° C. and treated with sodium bis(trimethylsilyl)amide (2.2 mL, 1.0 M, 2.2 equiv) drop wise over 5 min and stirred for 30 min. After adding benzoyl chloride (140 μl, 1.2 mmol, 1.2 eq), the reaction mixture was warmed up to room temperature and stirred for an additional 1.5 h. The solution was cooled to 0° C. and quenched with water (5 mL). The resulting solution was diluted with ethyl acetate and washed successively with water and saturated aqueous NaCl, dried over MgSO4, filtered and concentrated. Purification by MPLC (1-40% ethyl acetate in heptane gave 2-(benzhydrylidene-amino)-2-benzoyl-hex-5-enoic acid tert-butyl ester (477 mg, 1 mmol, 100%).
