A STUDY OF THE STEREOCHEMISTRY OF THE DEALKOXYCARBONYLATION OF SOME SULFUR-SUBSTITUTED CYCLOPROPANES

2-sulfenyl- and 2-sulfonyl-phenyl groups can affect the stereochemistr y of the products in the reaction of some ester-stabilized cyclopropyl carbanions. As these substituents are not particularly effective chel ating groups, the possibility of the intervention of a ct anomeric eff ect between the sulfur atom and the more extended orbital lobe of the cyclopropyl carbanion is considered. Evidences of the intermediacy of a pyramidal ester enolate are presented. The dimethyl 3-isopropyl-2-ph enylsulfonyl-1,1-cyclopropane dicarboxylate 12 undergoes dealkoxycarbo nylation, probably through a ring-opening ring-closure process, to giv e the corresponding monoester 15 with complete control of the relative stereochemistry of the three substituents.