Cyclopropanone enolate equivalents

The formation and decomposition of the enol sulphite (195) derived from the ketol (194) is now reported in full.174 A cyclopropanone (196), or an equivalent dipolar intermediate resulting from loss of S02, has been trapped as the diene-addition product (197) with furan. 

Vinyl cyclopropanols have been prepared by the addition of alkenyl Grignard reagents to a variety of cyclopropanone equivalents. Upon treatment with acid, the vinyl cyclopropanols rearrange to a-substituted cyclobutanones. Alternatively, a variety of a-heteroatora-substituted cyclopropyllithiura reagents have been developed. These react with aldehydes and ketones to afford cyclopropylcarbinols which also rearrange to cyclobutanones under acid catalysis.Lastly, vinyl cyclopropanols and cyclopropylcarbinols have been prepared by the cyclopropanation of enol silyl... 

Reaction of cyclopropanone ethyl hemiacetal with methylmagnesium bromide and two equivalents of cyclohexanone lithium enolate provides a very interesting and highly stereospecific synthesis of tricyclic cycloheptanones a serendipitous reaction... 

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