Abstract

Protonation of the highly reactive 1:1 intermediates produced in the reaction between tributylphosphine and dimethyl acetylenedicarboxylate by 3-hydroxy-2-methyl-4   H-pyran-4-one leads to vinyltributylphosphonium2Cl2 at room temperature to produce dimethyl 2-[(2-methyl-4-oxo-4 3-yl)oxy]-2-butenedioate (1:1 mixtures of yields. H-pyran-Eand Z isomers) in fairly good salts, which undergo an addition-elimination reaction in CH