Ni-Catalyzed direct iminoalkynylation of unactivated olefins with terminal alkynes: facile access to alkyne-labelled pyrrolines

Abstract

The direct iminoalkynylation of unactivated olefins with terminal alkynes is achieved for the first time by nickel-catalyzed cascade iminyl-radical cyclization/Sonogashira-type coupling of γ,δ-unsaturated oxime esters under mild conditions. This transformation allows for rapid construction of two challenging C(sp³)–N and C(sp³)–C(sp) bonds in a single step and enables facile access to various N-heterocycles including the challenging fused and spiro ones. Furthermore, the avoidance of using pre-activated alkynylating reagents and the tolerance of γ-H in oxime esters make it a straightforward and practical approach for the synthesis of alkyne-labelled pyrrolines, which widely exist in pharmaceutically relevant architectures. The use of readily available coupling partners, broad substrate scope, good functional group compatibility and versatile product derivatizations bode well for the widespread applications of this method in synthetic chemistry, biochemistry and materials science.