Facile Conversion of Cyclopropanols into Linear Conjugate Enones

Photocatalytic Stoichiometric Oxidant-Free Synthesis of Linear Unsaturated Ketones from 1,2-Disubstituted Cyclopropanols

A one-step catalytic oxidant-free synthesis of unsaturated ketones from 1,2-disubstituted cyclopropanols is reported. Previously for this transformation, only two- and three-step protocols have been developed. The reaction proceeds under irradiation with visible light in the presence of catalytic amounts of both an acridinium photocatalyst and a cobaloxime complex. 2-Aryl-substituted cyclopropanols react giving α,β-unsaturated ketones, while dehydrogenative ring opening of 2-alkyl-substituted substrates affords mixtures of α,β- and β,γ-enones. The reaction starts with one-electron oxidation of a cyclopropanol to cyclopropyloxy radical, presumably, by the photoexcited acridinium catalyst. We also found that Co(dmgBF2)2(MeCN)2 complex under an air atmosphere and irradiation with blue LEDs or upon heating can serve as a hydroxycyclopropane oxidant.

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

The ring-opening/cyclization of cyclopropane derivatives has drawn great attention in the past several decades. In this review, recent efforts in the development of oxidative radical ring-opening/cyclization of cyclopropane derivatives, including methylenecyclopropanes, cyclopropyl olefins and cyclopropanols, are described. We hope this review will be of sufficient interest for the scientific community to further advance the application of oxidative radical strategies in the ring-opening/cyclization of cyclopropane derivatives.

Stereoselective synthesis of α-methyl and α-alkyl ketones from esters and alkenes via cyclopropanol intermediates

Alkenes bearing a stereocenter in the allylic position were found to undergo Kulinkovich hydroxycyclopropanation with good diastereoselectivity. For the isomerization of the resulting cyclopropanols to diastereomerically enriched α-methyl ketones, a new mild regioselective method has been developed. A sequence of stereoselective cyclopropanation and cyclopropanol ring opening was successfully employed for the construction of the C20 stereocenter in steroids.

Synthesis of γ-keto sulfones by copper-catalyzed oxidative sulfonylation of tertiary cyclopropanols

Preparation of γ-keto sulfones via ring-opening sulfonylation of cyclopropanols.