Triphenyl(3,4,5-trimethoxybenzyl)phosphonium bromide → 4-Bromo-6-[(Z)-2-(3,4,5-trimethoxyphenyl)vinyl]-1,2-di(tert-butyldimethylsilyloxy)benzene

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A suspension of 3,4,5-trimethoxybenzyltriphenylphosphonium bromide (1.69 g, 3.23 mmol) in tetrahydrofuran (30 mL) was cooled to 0° C. and butyllithium (2 mL of a 1.6 N solution in hexane, 3.23 mmol) was added dropwise. The brick red solution was stirred at 0° C. for 20 min, then a solution of 19 (0.96 g, ca 2.2 mmol) in tetrahydrofuran (12 mL) was added dropwise. The temperature was allowed to rise to room temperature overnight, than the reaction was diluted with tert-butylmethyl ether (ca 100 mL) and washed with water (ca 50 mL, containing 1 mL 2N HCl) then brine (30 mL). The organic layer was dried over sodium sulphate and the solvent removed under reduced pressure to give a crude which was purified by column (elution with cyclohexane:AcOEt 10:1) to give 0.75 g of 20 still impure with 20% of the E isomer.

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