Copper(II)-Catalyzed Aminohalogenation of Alkynyl Carbamates

A useful aminohalogenation reaction for the cyclization of O-alkynyl carbamates under copper catalysis has been developed. N-Halosuccinimides have been used as a halogen source. The intramolecular C−N bond formation occurs selectively affording haloalkylidene substituted heterocycles. Just in the case of α,α-cyclohexyl-substituted propargyl carbamate, the alkoxyhalogenation pathway was operative. The mechanism for the two alternative reaction pathways was investigated by modeling the corresponding transition states at the DFT level.