One‐pot synthesis and chiral analysis of cyclopropane derivatives

A user‐friendly, one‐pot procedure was developed to access racemic as well as enantiomerically enriched cyclopropanes. Thus, the cyclopropanation of olefin ( 3 ) was performed using Meldrum's acid ( 4 ) or dimethyl malonate ( 5 ) and diacetoxyiodobenzene PhI(OAc) 2 ( 6 ) or iodosyl benzene PhI=O ( 7 ) for in situ generation and decomposition of the phenyliodonium ylide 1 and 2, respectively. The reaction proceeds well with 5 mol% of achiral rhodium (II)‐catalyst [Rh 2 (OAc) 4 ] and a 10‐fold excess of olefin affording the cyclopropane derivates 10 and 11, respectively, with high yield. The system is compatible with chiral Rh(II)‐catalysts 8 and 9 and an enantiomeric excess up to 66% was achieved. An effective baseline separation of the enantiomers of the resulting cyclopropane derivatives was achieved using gas chromatography on the chiral stationary phase Chirasil‐β‐dex. Chirality 17:44–50, 2005. © 2004 Wiley‐Liss, Inc.