Beilstein Journal of Organic Chemistry (Apr 2021)

A chromatography-free and aqueous waste-free process for thioamide preparation with Lawesson’s reagent

  • Ke Wu,
  • Yichen Ling,
  • An Ding,
  • Liqun Jin,
  • Nan Sun,
  • Baoxiang Hu,
  • Zhenlu Shen,
  • Xinquan Hu

DOI
https://doi.org/10.3762/bjoc.17.69
Journal volume & issue
Vol. 17, no. 1
pp. 805 – 812

Abstract

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After completing the thio-substitution with Lawesson’s reagent, ethanol was found to be effective in the decomposition of the inherent stoichiometric six-membered-ring byproduct from the Lawesson’s reagent to a highly polarized diethyl thiophosphonate. The treatment significantly simplified the following chromatography purification of the desired thioamide in a small scale preparation. As scaling up the preparation of two pincer-type thioamides, we have successfully developed a convenient process with ethylene glycol to replace ethanol during the workup, including a traditional phase separation, extraction, and recrystallization. The newly developed chromatography-free procedure did not generate P-containing aqueous waste, and only organic effluents were discharged. It is believed that the optimized procedure offers the great opportunity of applying the Lawesson’s reagent for various thio-substitution reactions on a large scale.

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