Process for preparing ylid compounds

摘要

Ylid compounds of the formula II <IMAGE> where X<+> is either a trisubstituted phosphonio group or a diesterified phosphono group together with a cation, are prepared by treating an alpha -hydroxycarboxylic acid compound of the formula XI <IMAGE> where Xo is a reactive esterified hydroxyl group, with a trisubstituted phosphine compound or with a phosphite compound. The meaning of the other symbols is given in Claim 1. The ylid compounds can be used as intermediates for preparing bicyclic thiaaza compounds.