1,10‐Phenanthroline Copper(I) Complexes with A3 Coupling to Access Allenes for Cycloaddition Reactions

Abstract

AbstractPropargylamines are significant building blocks for the generation of polyfunctional amino analogues, natural products, and pharmacologically active drugs. Herein we report the most straightforward approach is to use 1,10‐phenanthroline copper(I) complexes as a catalyst to promote the (Alkyne‐Alkyne‐Amine) A3 coupling reaction between cyclic secondary amines and two terminal alkynes that generates a ketimine intermediate in situ through hydroamination, which subsequently interacts with the alkenyl copper complex to produce tetrasubstituted propargylamine. In the addition of zinc halide, the propargylamines converted into trisubstituted allenes with up to 90% yield. When Sc(OTf)3 is used to perform the [4+2] cycloaddition reaction with enophile (alkene), the cyclized product obtained in up to 72% yield. On the other hand, the allene was subjected to a metal‐free intermolecular cyclization reaction to produce the highly substituted pyridine derivative, although this provides only up to 30% yield.