Preparation and structure of some sulfanylpropenylidene derivatives of Meldrum’s acid

Abstract

Condensation of Meldrum’s acid with the 3-sulfanylpropenal derivatives 7a and 7b gives the 3-sulfanylpropenylidene derivatives 2a and 2b, respectively. NMR and X-ray analysis of 2a and 2b show that the electron-donating group conjugates with the electron-withdrawing dioxanedione moiety but the effect is much less pronounced than in analogous dialkylamino derivatives 1. There is little or no conjugation of the ortho-alkylsulfanyl group to the dioxanedione moiety in the benzylidene derivatives 4a and 4b.