Abstract

Protonation of the highly reactive 1:1 intermediates produced in the reaction between triphenylphosphine (or tributylphosphine) and dialkyl acetylenedicarboxylates by acetylacetone leads to sterically congested phosphorus ylides, which undergo an intermolecular Wittig reaction with ninhydrin and concomitant annulation in CH temperature to produce dialkyl 3,3-diacetyl-3   2Cl2 at room a-hydroxy-8-oxo-2,3,3a,8-a]indene-1,2-dicarboxylates in fairly high yields. tetrahydrocyclopenta[