Reactivity of a Cationic Bismuth Amide towards Unsymmetric Heterocumulenes

Abstract

The reactivity of a literature-known, ring-strained bismuth amide cation towards a range of unsymmetric heterocumulene substrates has been investigated. Reactions with ketenes R2C=C=O (R=Me, Ph), isocyanates R'N=C=O, and isothiocyanates R'N=C=S (R’=Ph, 4-CF3-C6H4) proceed via facile insertion of the heterocumulene in the Bi−N bond of the cationic bismuth amide. Unexpectedly pronounced differences in the regioselectivity of these insertion reactions have been observed, yielding a rich variety of heterocycle motifs (BiC2NC2, BiC2NCO, BiC2NCS, BiC2NCN), some of which are unprecedented. Parameters that control the regioselectivity of the insertion reactions have been identified and are discussed based on experimental and theoretical investigations. Analytical techniques applied in this work include heteronuclear and two-dimensional NMR spectroscopy, IR spectroscopy, elemental analysis, single-crystal X-ray diffraction analyses, and DFT calculations.