Ammonium Chloride → Methyl 8-(p-chlorophenylsulfonamido)-4-[3-(3-pyridyl)-2-propenyl]octanoate

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Reaction Steps

To a suspension of 0.545 g of 3-pyridylmethyltriphenylphosphonium chloride in 6 mL tetrahydrofuran is added slowly 1.6 mL of 1.61 M potassium t-butoxide in tetrahydrofuran and the mixture is stirred at room temperature for 1 hour. A solution of 0.454 g of methyl 8-(p-chlorophenylsulfonamido)-4-(formylmethyl)octanoate in 1 mL tetrahydrofuran is added slowly and then stirred for 18 hours at room temperature. The reaction mixture is poured into saturated ammonium chloride and extracted with ethyl acetate (3×15 mL). The combined organic extracts are dried, filtered and evaporated to give a dark residue which is purified by flash chromatography to obtain, as a light amber oil, methyl 8-(p-chlorophenylsulfonamido)-4-[3-(3- pyridyl)-2-propenyl]-octanoate. The product is a mixture of cis and trans isomers, the major component being the cis isomer. The above product is dissolved in 5 mL methylene chloride in a crystallizing dish and the solution is irradiated for 5 hours under UV light. The organic layer is diluted with methylene chloride and washed with aqueous sodium thiosulfate. The organic phase is dried, filtered and evaporated. The residue is purified by preparative thin layer chromatography to obtain a clear oil identified as about a 1:1 mixture of cis and trans isomers.

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