Synthesis of Halogenated Cyclic Enamines from Cyclic N‐2‐En‐4‐ynyl‐N‐1‐ynylamides and N‐Propargyl‐N‐1‐ynylamides via a Tandem Iron Halide Promoted N‐to‐C Shift‐Aza‐Prins Cyclization Sequence

Abstract

AbstractA facile and efficient N‐to‐C allyl shift‐aza‐Prins cyclization sequence of cyclic N‐2‐en‐4‐ynyl‐N‐1‐ynylamides is promoted by iron(III) chloride, generating chloro‐containing bridged bicyclic enamines in minutes and in high yields. This reaction involves an unprecedented formation of a ketenimine via Fe(III)‐mediated N‐to‐C allyl rearrangement, followed by aza‐Prins cyclization. This sequence can also be applied to the generation of brominated cyclobutenamine derivatives using Fe(III) bromide and N‐propargyl‐N‐1‐ynylamides.magnified image