Iron-catalyzed synthesis of cyclopropanes by <i>in situ</i> generation and decomposition of electronically diversified diazo compounds
作者:Emmanuelle M. D. Allouche、Afnan Al-Saleh、André B. Charette
DOI:10.1039/c8cc07060a
日期:——
The modular synthesis of a variety of trans 1,2-disubstituted cyclopropanes in a safe and user-friendly one-pot iron-catalyzed cyclopropanation reaction is described. Easily synthesized N-nosylhydrazones are used as diazo precursors, allowing the in situ generation of electron-rich diazo compounds under mild reaction conditions and their direct participation in the cyclopropanation reaction.
We describe the first general method for the metal-free cyclopropanation of alkenes by using N-tosylhydrazones as an in situ source of diazo compounds. This new method works with a wide variety of alkenes (styrene derivatives, dienes, enynes, and electron-deficient alkenes) by using N-tosylhydrazones derived from various ketones or aldehydes (aromatic, aliphatic, enones). The reaction is performed
Cyclopropane–alkene metathesis by gold(<scp>i</scp>)-catalyzed decarbenation of persistent cyclopropanes
作者:Mauro Mato、Inmaculada Martín-Torres、Bart Herlé、Antonio M. Echavarren
DOI:10.1039/c9ob00359b
日期:——
A gold(I)-catalyzed cyclopropane–alkene metathesis has been demonstrated with two new families of cyclopropane derivatives of naphthalene and phenanthrene (benzo-fused norcaradienes). In this process, metal carbene units are transferred from a persistent cyclopropane to an alkene, upon release of naphthalene or phenanthrene, allowing the diastereoselective synthesis of a wide range of aryl and vinyl
A dirhodium(II) complex with N-perfluorooctylsulfonylprolinate ligands is found to catalyze the cyclopropanation of olefins with simple aryl diazomethanes. In contrast to previously reported dirhodium(II) catalysts, the present complex works well not only with very electron-rich olefins such as enol ethers, but also with styrenes. Consequently, the present catalyst allows to prepare functionalized diarylcyclopropanes in moderate yields with good diastereoselectivity for the cis product, whereas the enantioselectivity of the reaction appears negligible. (C) 2011 Elsevier Ltd. All rights reserved.
Electronic properties of three-membered rings. II. Transmission of conjugation by the cyclopropane ring