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Regioselective cyclopropanation of 2-phenylsulfonyl 1,3-dienes

✍ Scribed by Jan-E. Bäckvall; Claes Löfström; Seppo K. Juntunen; Matthew Mattson

Publisher
Elsevier Science
Year
1993
Tongue
French
Weight
253 KB
Volume
34
Category
Article
ISSN
0040-4039

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✦ Synopsis

Begioselective cyclopropanation of 2-phenylsulfonyl 13-dienes at either double bond was achieved by employing two different reagents. Sulfur ylide 1 cesulted in a regiospeciKc cyclopropanation at the electron deficient double bond whereas an iron carbene, thermally generated from Sn, gave cyclopropanation exclusively at the electron rich double bond.

Electron-defiiient conjugated dienes have recently attracted considemble interest in organic synthesis.'" We 1*5 and others 2*3 have explored the synthetic utility of 2-phenylsulfonyl1.3~dienes and demonstrated their use in cycloaddition teactions and as multicoupling reagents. Fmtbermore, regioselective functionahxation of one of the double bonds of these sulfonyl dienes leads to useful synthetic intermediates.1b~5 previously we reported selective epoxidation reactionslb which allow the pteparation of either regioisomer of the monoepoxide. One objective with our studies was to extend these epoxidations to related regioselective cyclopropanation reactions. This would lead to the corresponding vinylcyclopropanes. which are an important class of ~ompotmds.~ In this communication we report that reaction of 2-phenylsulfonyl 1.3~dienes with electrophilic and nucleophilic cyclopropanation reagents lead to highly mgioselective cyclopropanation of either double bond (Scheme J).

ZPhenylsulfonyl 134enes have one electron-deficient and one electron-rich double bond. For the cyclopropanation of the former double bond we chose the sulfur ylid magent l,s which is known to cyclopropanate the double bond of @-unsaturated ketones and esters. Reaction of Z(phenylsulfonyl)-

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