Asymmetric Cyclopropanation with 4-Aryloxy-1-sulfonyl-1,2,3-triazoles: Expanding the Range of Rhodium-Stabilized Donor/Acceptor Carbenes to Systems with an Oxygen Donor Group

Rhodium-catalyzed enantioselective synthesis of 1-phenoxycyclopropane-1-carbaldehydes by intermolecular cyclopropanation of terminal alkenes followed by imine hydrolysis is described. This methodology utilizes 4-aryloxy-1-sulfonyl-1,2,3-triazoles as the carbene precursors and the chiral dirhodium(II) tetracarboxylates Rh2(S-NTTL)4 or Rh2(S-DPCP)4 as the catalysts. These reactions are considered to proceed via rhodium-stabilized donor/acceptor carbene intermediates, and these studies demonstrate that a heteroatom donor group is compatible with an enantioselective transformation.