反应详情

The preparation of XIII begins with the known methyl 3-(bromomethyl)benzoate. This halide is heated in xylene solution with triphenylphosphine to yield (3-methoxycarbonylbenzyl)triphenylphosphonium bromide. The phosphonium salt is converted to the ylide with sodium ethoxide in ethanol and the ylide caused to react with acetaldehyde to yield ethyl 3-(1-propenyl)benzoate. [Note that the ethyl ester has been obtained as a result of transesterification with solvent ethanol.] The ester is heated with N-bromosuccinimide in carbon tetrachloride for an extended period to yield ethyl 3-(3-bromo-1-propenyl)benzoate. This compound is treated with the anion derived from methyl methylthiomethyl sulfoxide as described in previous examples. The resulting dimethyl mercaptal S-oxide is hydrolyzed with acid catalysis to the aldehyde reagent XIII.