VINYLTRIPHENYLPHOSPHONIUM SALT MEDIATED PREPARATION OF DIALKYL 2H-1-BENZOPYRAN-2,3-DICARBOXYLATES - AN EFFICIENT ONE-POT SYNTHESIS OF 2H-CHROMENE DERIVATIVES

Protonation of the highly reactive 1:1 intermediates produced in the r eaction between triphenylphosphine and dialkyl acetylenedicarboxylates by 2-hydroxybenzaldehyde leads to vinyltriphenylphosphonium salts, wh ich undergo an intramolecular Wittig reaction to produce dialkyl 2H-1- benzopyran-2,3-dicarboxylates in high yields.