Rh2(II)-Catalyzed Ring Expansion of Cyclobutanol-Substituted Aryl Azides To Access Medium-Sized N-Heterocycles

J Am Chem Soc. 2017 Apr 12;139(14):5031-5034. doi: 10.1021/jacs.7b01833. Epub 2017 Mar 29.

Abstract

A new reactivity pattern of Rh2(II)-N-arylnitrenes was discovered that facilitates the synthesis of medium-sized N-heterocycles from ortho-cyclobutanol-substituted aryl azides. The key ring-expansion step of the catalytic cycle is both chemoselective and stereospecific. Our mechanistic experiments implicate the formation of a rhodium N-arylnitrene catalytic intermediate and reveal that sp3 C-H bond amination of this electrophilic species is competitive with the ring-expansion process.