Stereoselective Synthesis of β,γ-Unsaturated Ketones by Acid-Mediated Julia-Type Transformation from 2-(1-Hydroxyalkyl)-1-alkylcyclopropanols

Abstract

An efficient transformation of 2-(1-hydroxyalkyl)-1-alkylcyclopropanols, obtained from α,β-unsaturated ketones, to β,γ-unsaturated ketones was achieved by trifluoroacetic acid (TFA)-mediated reaction.

Key words

β,γ-unsaturated ketone - methylene insertion - cyclopropanol - carbocation - stereoselective

References and Notes

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7

Treatment of diastereomixture of 2a with 5 equiv of TFA at r.t. for 6 h did not change the E/Z ratio. An addition of 1 equiv of H₂O to this system did not also change the ratio. These experiments mean that the diastereoselectivity does not come from isomerization of the initial product.