Selective Synthesis of Unsaturated Imines via [py2TiI2(NPh)]2-Catalyzed Alkyne Carboamination

Strongly Lewis acidic titanium iodo complexes catalyze selective inter- and intramolecular carboamination of alkynes to give unsaturated imines. Computations and mechanistic experiments indicate that unsaturated imines are not the direct product of alkyne carboamination as previously reported, but result from the ring-opening rearrangement of cyclopropylimines instead. Reactions of cyclopropylimines with titanium complexes confirm the generation of acyclic imines from an iminocyclopropane rearrangement, however it is noted that this rearrangement is specific to titanium-iodide species.