Palladium-mediated synthesis of novel meso-chiral porphyrins: cobalt-catalyzed cyclopropanation

A series of novel meso-chiral porphyrins were effectively synthesized from reactions of 5,15-dibromo-10,20-diarylporphyrins with readily available chiral alcohols and amides via palladium-mediated C–N and C–O bond formations. Cobalt complexes of these chiral porphyrins were prepared and shown to be effective catalysts for cyclopropanation of styrene with ethyl diazoacetate under mild and practical conditions, affording the desired cyclopropane ester as a trans-dominant form in excellent yields. Due to orientation and flexibility of the chiral appendages, only low enantioselectivity was observed.