ASYMMETRIC CYCLOPROPANATION OF ALKENES CATALYZED BY A RHODIUM CHIRAL FORTRESS PORPHYRIN

While a number of efficient asymmetric catalysts exist for the cyclopropanation of alkenes by diazo esters, all provide diastereomeric mixtures in which the anti product predominantes. We report here the synthesis and characterization of a chiral rhodium porphyrin catalyst that provides predominantly the syn isomers, with very good diastereoselectivity in some cases. However, the enantioselectivities observed are modest.