A study of the stereochemistry of the dealkoxycarbonylation of some sulfur-substituted cyclopropanes.

Bernard AM;Piras PP;Cocco MT;CONGIU, CENZO;ONNIS, VALENTINA

1997-01-01

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Abstract

2-sulfenyl- and 2-sulfonyl-phenyl groups can affect the stereochemistry of the products in the reaction of some ester-stabilized cyclopropyl carbanions. As these substituents are not particularly effective chelating groups, the possibility of the intervention of a ct anomeric effect 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-phenylsulfonyl-1,1-cyclopropane dicarboxylate 12 undergoes dealkoxycarbonylation, probably through a ring-opening ring-closure process, to give the corresponding monoester 15 with complete control of the relative stereochemistry of the three substituents.