n-Butyllithium (0.37 mL, 0.59 mmol, 1.6 M in hexanes) was added dropwise over 5 min to a solution of 3,4,5-trimethoxybenzylphosphonium bromide (0.27 g, 0.52 mmol) in THF (3 mL) at −10° C. The reaction mixture was stirred at this temperature for 15 min then cooled to −70° C. and a solution of 41 (0.10 g, 0.24 mmol) in THF (3 mL) was added and the reaction mixture was allowed to warm to rt with stirring overnight (16 h). The reaction mixture was cooled to 0° C. and water was added. The reaction mixture was extracted with t-BuOMe (3×) and the organic phase was washed successively with water and brine, dried (Na2SO4) and evaporated to dryness to give crude product (0.3 g). Purification by column chromatography (SiO2 2:98 EtOAc:cyclohexane) gave 42 (83 mg, 60%) as an 85:15 mixture of Z:E isomers.
