Alcohols, carbonylation cyclopropylcarbinyl

Later Julia and coworkers developed another important mode of ring breaking addition of Grignard compounds or reduction converts the ester 22 to the corresponding alcohols which are startingpoints for a cyclopropylcarbinyl/homoallyl cation rearrangement. After acid treatment p/y-unsaturated carbonyl compounds (e.g. 23) can be isolated, which sometimes isomerize to the oc,(3-unsaturated systems 10). 

The reduction of methyl 2-siloxycyclopropanecarboxylates can also be started at the ester function when lithium aluminum hydride in ether is the reagent. The resulting alcohols undergo the wellknown cyclopropylcarbinyl/homoallyl rearrangement upon treatment with acid to provide P/y-unsaturated carbonyl compounds 117. These are synthesized isomerically pure and in good yields in a number of cases, if the two-phase-system 2N hydrochloric acid/pentane is employed 78). Otherwise the very easy isomerization to the conjugated a,p-unsaturated compounds 118 occurs to some extend, which can intentionally be completed by base catalysis. 

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