Reactions of diazoalkanes with unsaturated compounds 15. Catalytic reactions of unsaturated carbonyl compounds and their derivatives with diazomethane

The present study concerned with the influence of the nature of the acetal fragment in unsaturated compounds on the reactivity of the C=C bond in cyclopropanation reactions with diazomethane catalyzed by copper and palladium compounds. The acetal substituents at the α- or γ-position with respect to the C=C bond were found to exert an activating effect on the yields of cyclopropanation products compared to the starting unsaturated carbonyl compounds, which give 1,3-dipolar cycloaddition adducts with CH₂N₂ as by-products. Cyclopropanation of the double bonds appeared to be most efficiently catalyzed by Pd(acac)₂. Dedicated to Corresponding Member of the Russian Academy of Sciences E. P. Serebryakov on the occasion of his 70th birthday. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 979–983, April, 2005.     

Synthesis of 1,2,3-trisubstituted cyclopropanes by MIRC reactions of dithianyllithiums with monocarboxylic vinyl epoxide analogues

A variety of cyclopropane derivatives bearing stereochemistry at all three positions on the ring were readily obtained in a high yield of 76-92% and high stereoselectivity (trans:cis > 95:5) when the monocarboxylic vinyl epoxide analogues reacted with dithianyllithiums in the presence of HMPA. This reaction was supposed to be a tandem conjugation addition-opening epoxide ring sequence.     

Allylgallation of cyclopropenes. Crystal structure of a novel cyclopropylgallium compound prepared by allylgallation of hydroxy-bearing cyclopropene

Allylgallation of cyclopropenes with allylgallium sesquibromide has been investigated; a novel cyclopropylgallium compound was isolated via allylgallation of hydroxy-bearing cyclopropene, and its structure was fully characterized by X-ray crystallography.     

Stereoselective CH Borylations of Cyclopropanes and Cyclobutanes with Silica‐Supported Monophosphane–Ir Catalysts

Heteroatom‐directed C?H borylation of cyclopropanes and cyclobutanes was achieved with silica‐supported monophosphane–Ir catalysts. Borylation occurred at the C?H bonds located γ to the directing N or O atoms with exceptional cis stereoselectivity relative to the directing groups. This protocol was applied to the borylation of a tertiary C?H bond of a ring‐fused cyclopropane.     

Facile,Highly Stereoselective Synthesis of Cyclopropyl Benzoimidazoles via Cyclopropanation of Olefin with Arsonium Ylides

A facile and highly stereoselective methodology for the preparation of highly functionalized trans-1,2-cyclopropanes containing benzoimidazolyl, cyano, aryl, and carbonyl groups 3 is described. Arsonium bromides 2 reacted with electron-deficient olefins 1 in the presence of KF·2H₂O to provide 3 exclusively with high stereoselectivity in moderate to good yields.     

Synthesis of (Het)aryl 2-(2-hydroxyaryl)cyclopropyl Ketones

A simple general method for the synthesis of 1-acyl-2-(ortho-hydroxyaryl)cyclopropanes, which belong to the donor–acceptor cyclopropane family, has been developed. This method, based on the Corey–Chaykovsky cyclopropanation of 2-hydroxychalcones, allows for the preparation of a large diversity of hydroxy-substituted cyclopropanes, which can serve as promising building blocks for the synthesis of various bioactive compounds.