Synthesis of Secondary Amides from Thiocarbamates
Pieter Mampuys, Eelco Ruijter, Romano V. A. Orru and Bert U. W. Maes*
*Organic Synthesis, Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium, Email: bert.maesuantwerpen.be
P. Mampuys, E. Ruijter, R. V. A. Orru, B. U. W. Maes, Org. Lett., 2018, 20, 4235-4239.
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The reaction of readily accessible and bench-stable substituted S-phenyl thiocarbamates and Grignard reactants provides secondary amides. Oxidative workup allows recycling of the thiolate leaving group. This amide synthesis is especially suitable for the preparation of challenging amides.
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You could also stop the reaction after two hours if you are not interested in the recuperation of the disulfide and obtain the amide in the same yield as reported in our publication. This would of course reduce the total reaction time from 20 hours to 2 hours. A disadvantage of not performing the second step is that thiophenol is still present in the reaction mixture, with its well known unpleasant odour. This is not so nice for the researcher to perform the work-up. Moreover, after the transformation into phenyl disulfide the thiophenol smell disappears and we could recover our waste component.
Pieter Mampuys, May 15, 2019