Abstract
Multicomponent reactions (MCRs) represent one of the most elegant and powerful synthetic strategies for constructing complex molecular scaffolds in natural products and bioactive molecules. By combining radical cascade reactions, the rapid development of multicomponent methodologies involving the radical 1,4-addition of 1,3-enynes has been notable in the synthetic chemistry of complex unsaturated molecules. In this study, an iron-catalyzed 1,4-alkylarylation of 1,3-enynes with lithium aryl borates and unactivated alkyl bromides has been achieved using an iron-NiXantphos catalyst, delivering various densely substituted allenes in high yield with excellent regioselectivity. Remarkably, the mild reaction conditions ensure high chemoselectivity and compatibility with different functional groups. Furthermore, mechanistic investigations employing radical probes have substantiated the involvement of propargylic and allenylic radical intermediates. This finding signifies the process as a radical cascade of multicomponent couplings poised to become an effective strategy for synthesizing complex organic compounds.