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 [Rh2(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-beta-dex.
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