Acceptor/Acceptor‐Substituted Diazo Reagents for Carbene Transfers: Cobalt‐Catalyzed Asymmetric Z‐Cyclopropanation of Alkenes with α‐Nitrodiazoacetates

Surprisingly cis-tematic! The cobalt(II) complex of a D2-symmetric chiral porphyrin is an effective catalyst for asymmetric cyclopropanation with α-nitrodiazoacetates (see scheme). The catalytic system is general and suitable for electron-sufficient, -neutral, and -deficient alkenes, forming the corresponding cyclopropane nitroesters in high yields. In addition to high diastereo- and enantioselectivity, the catalytic process exhibits atypical Z selectivity.