The first example for the asymmetric synthesis of allenes by the Doering–LaFlamme allene synthesis with enantiopure cyclopropylmagnesium carbenoids

The reaction of lithium α-sulfinyl carbanion of enantiopure dichloromethyl p-tolyl sulfoxide with α,β-unsaturated carbonyl compounds gave optically active 1-chlorocyclopropyl p-tolyl sulfoxides having a carbonyl group with high asymmetric induction from the sulfur chiral center. Reduction of the carbonyl group followed by treatment with Grignard reagent, the 1-chlorocyclopropyl p-tolyl sulfoxides resulted in the formation of enantiopure allenic alcohols via the Doering–LaFlamme-type rearrangement of enantiopure cyclopropylmagnesium carbenoid intermediates. This is the first example for the asymmetric synthesis of allenes by the Doering–LaFlamme allene synthesis.

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