The reaction of vinyl selenones with di-(-)-bornyl malonate and sodium hydride occurred with low diastereoselectivity and afforded a mixture of two diastereomeric cyclopropane derivatives in comparable yields. These, however, could be easily separated by chromatography. Removal of the bornyl group afforded highly enantiomerically enriched cyclopropanes. An example of the simple conversions of these cyclopropanes into useful cyclopropane alpha-amino acids is also illustrated. The syntheses of several vinyl selenides and selenones are also described. (C) 2009 Elsevier Ltd. All rights reserved.
Asymmetric Rh(II)-Catalyzed Cyclopropanation of Alkenes with Diacceptor Diazo Compounds: <i>p</i>-Methoxyphenyl Ketone as a General Stereoselectivity Controlling Group
作者:Vincent N. G. Lindsay、Cyril Nicolas、André B. Charette
DOI:10.1021/ja201237j
日期:2011.6.15
α-PMP-ketone group were found to be effective carbene precursors for the highly stereoselective Rh(2)(S-TCPTTL)(4)-catalyzed cyclopropanation of alkenes (EWG = NO(2), CN, CO(2)Me). The resulting products were readily transformed into a variety of biologically relevant enantiopure molecules, such as cyclopropane α- and β-amino acid derivatives. Different mechanistic studies carried out led to a rationale for the