Stereodivergent Intramolecular C(sp3)-H Functionalization of Azavinyl Carbenes: Synthesis of Saturated Heterocycles and Fused N-Heterotricycles

A general approach for the formation of five-membered saturated heterocycles by intramolecular C(sp(3))-H functionalization is reported. Using N-sulfonyl-triazoles as Rh(II) azavinyl carbene equivalents, a wide variety of stereo defined cis-2,3-disubstiiuted tetrahydrofurans were obtained with good to excellent diastereoselectivity from readily available acyclic precursors. The reaction is shown to be amenable to gram scale, and judicious choice of reaction conditions allowed for stereodivergence, providing selective access to the trans diastereomer in good yield. The resulting products were shown to be valuable intermediates for the direct preparation of fused N-heterotricydes in one step by intramolecular C-H amination or Pictet-Spengler cyclization.