Cycloheptanones homoenolates

In the presence of a Lewis acid, alkyl 2-silyloxycyclopropanecarboxylates (14) react with a wide range of carbonyl compounds to give a diester (15), which has b n converted to a variety of furan derivatives (Scheme 18). An interesting use of the oxyanionic tautomer of a homoenolate involves the reaction of a magnesium cyclopropanolate (12) with the lithium enolate of cyclohexanone, from which a tricyclic ring containing a functionalized cycloheptanone (13) is formed in a single step (Scheme 18). ... 

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