Rhodium-Catalyzed Enantioselective Cyclopropanation of Olefins

Significance

Diazocarbonyl compounds are well-known precursors of metal carbenes. In contrast, azavinyl carbenes 1 have not been employed in synthesis due to the limited availability of the α-diazoimines. These reactive intermediates are synthetic equivalents of formyl carbenes, from which both amine and aldehyde functions can be obtained by simple transformations, thus significantly expanding the scope of chiral molecules that can be synthesized via carbene-based methods. The authors reported a novel and efficient rhodium(II)-catalyzed asymmetric cyclopropanation that utilized stable and readily available N-sulfonyl 1,2,3-triazoles 2 as azavinyl carbene precursors. The carbenes readily react with olefins, providing cyclopropanecarboxaldehydes in excellent yield and enantioselectivity.