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Dichlorocyclopropanation and ring cleavage of bridgehead enol lactones. A stereocontrolled ring expansion sequence

โœ Scribed by K.J. Shea; W.M. Fruscella; W.P. England

Publisher
Elsevier Science
Year
1987
Tongue
French
Weight
246 KB
Volume
28
Category
Article
ISSN
0040-4039

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โœฆ Synopsis

Sequential dichlorocyclopropanation and ethoxide induced lactone cleavage of bridgehead enol lactones affords a stereocontrolled synthesis of 2-chlorocycloheptenones. Bridgehead enol lactones (2),' prepared by Type 2 intramolecular Diels-Alder cycloaddition of trienol esters (1) have been shown to be of value in the stereo-and regiocontrolled synthesis of six-membered rings* (eq. 1).

In an effort to develop the synthetic utility of bridgehead enol lactones, we report that the sequence of transformations involving dichlorocyclopropanation followed by reaction with ethanolic K,CO, provides a versatile synthetic entry into functionalized 2-chlorocycloheptenones.

The steps are outlined in Scheme 1.

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