Synthesis of cyclopropanols via cyclopropanation of zinc enolates

Diethylzinc-Mediated Radical 1,2-Addition of Alkenes and Alkynes

A novel diethylzinc-mediated radical 1,2-addition of perfluoroalkyl iodides to unactivated alkenes and alkynes is presented, which demonstrates a novel way to generate an ethyl difluoroacetate radical. This method is highly efficient and gives full conversions of the substrates, high yields of the products, and negligible byproducts and requires no column chromatography purifications. The mild conditions enable this protocol to exhibit excellent functional group compatibility.

General Synthesis of Cyclopropanols via Organometallic Addition to 1-Sulfonylcyclopropanols as Cyclopropanone Precursors

The addition of organometallic reagents to ketones constitutes one of the most straightforward synthetic approaches to tertiary alcohols. However, due to the absence of a well-behaved class of cyclopropanone surrogates accessible in enantioenriched form, such a trivial synthetic disconnection has received very little attention in the literature for the formation of tertiary cyclopropanols. In this work, we report a simple and high-yielding synthesis of 1-substituted cyclopropanols via the addition of diverse organometallic reagents to 1-phenylsulfonylcyclopropanols, acting here as in situ precursors of the corresponding cyclopropanones. The transformation is shown to be amenable to sp-, sp²-, or sp³-hybridized organometallic C-nucleophiles under mild conditions, and the use of enantioenriched substrates led to highly diastereoselective additions and the formation of optically active cyclopropanols.

Diastereo- and enantioselective preparation of cyclopropanol derivatives

The diastereoselective carbocupration reaction of alkoxy-functionalized cyclopropene derivatives, followed by a subsequent trapping of the resulting cyclopropylmetal species with an electrophilic source of oxygen (oxenoid) afforded various tetrasubstituted cyclopropanol derivatives in high diastereo- and enantiomeric ratios. Similarly, the enantioselective copper-catalyzed carbomagnesiation/oxidation (or amination) sequence on achiral nonfunctionalized cyclopropenes provided the desired cyclopropanol (and cyclopropylamine) derivatives in excellent diastereo- and enantiomeric excesses.

Zinc-Mediated C−C Bond Sigmatropic Rearrangement: A New and Efficient Methodology for the Synthesis of β-Diketones

A new and efficient methodology has been developed for the synthesis of beta-diketones from aromatic alpha-bromo ketones in the presence of Furukawa reagent under mild conditions. The present transformation is proposed to proceed via a Reformatsky-type reaction of alpha-bromo ketones, followed by C-C bond sigmatropic rearrangement of the aldolate intermediate to give beta-diketones in moderate to good isolated yields, while aliphatic alpha-bromomethyl ketones resulted in the formation of 2,4-disubstituted furans or cis-1,2-disubstituted cyclopropanols in moderate yields. The scope of this process was investigated, and a tentative mechanism was proposed.