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Homologation of Isocyanates with Lithium Carbenoids: A Straightforward Access to α-Halomethyl- and α,α-Dihalomethylamides

Vittorio Pace*, Laura Castoldi, Ashenafi Damtew Mamuye, Wolfgang Holzer

*Department of Pharmaceutical Chemistry – Division of Drug Synthesis, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria, Email: vittorio.paceunivie.ac.at

V. Pace, L. Castoldi, A. D. Mamuye, W. Holzer, Synthesis, 2014, 46, 2897-2909.

DOI: 10.1055/s-0034-1379209 (free Supporting Information)



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Abstract

Treatment of widely available isocyanates with monohalolithium and dihalolithium carbenoids provides α-halo- and α,α-dihaloacetamide derivatives. While monohalolithium carbenoids can be prepared by a smooth lithium-halogen exchange, the preparation of the corresponding dihalo compounds proved to be highly dependent on the base used to realize the deprotonation, with lithium 2,2,6,6-tetramethylpiperidine emerging as optimal.


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Key Words

amides, α-chloromethylamides, α-bromomethylamides, α-iodomethylamides, carbenoids, lithiation, halides, nucleophilic addition


ID: J66-Y2014