Synthesis of Isothiocyanates by Reaction of Amines with Phenyl Chlorothionoformate via One-Pot or Two-Step Process
Zheng-Yi Li, Hong-Zhao Ma, Chen Han, Hai-Tao Xi, Qi Meng, Xin Chen*, Xiao-Qiang Sun*
*Changzhou University, Changzhou, Jiangsu 213164, P. R. of China, Germany, Email: xinchencczu.edu.cn, xqsuncczu.edu.cn
Z.-Y. Li, H.-Z. Ma, C. Han, H.-T. Xi, Q. Meng, X. Chen, X.-Q. Sun, Synthesis, 2013, 45, 1667-1674.
DOI: 10.1055/s-0033-1338744 (free Supporting Information)
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A facile and efficient synthesis of isothiocyanates involves the reaction of amines with phenyl chlorothionoformate in the presence of solid sodium hydroxide by either a one-pot process or a two-step approach. The one-pot process is useful for preparing alkyl and electron-rich aryl isothiocyanates, whereas the two-step approach is more versatile.
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Note concerning excess amine in thiocarbamoylation step:
We have tried various additional bases for the thicarbamoylation. For example
with Et3N, the reaction didn't stop at the thiocarbamate stage, and
two different results were obtained:
1. For aliphatic amines and electron-rich anilines, the corresponding isothiocyanates were obtained in moderate to good yields (please see our previous publication: Synthesis, 2011, 3991-3996)
2. For aniline and election-deficient anilines, 0%-35% yield of isothiocyanates resulted, and the major isolated product was O-phenyl diethylcarbamothioate because of the dealkylation of Et3N by phenyl chlorothionoformate (please see Scheme 2 in Synthesis, 2013, 45, 1667-1674).
Xin Chen, August 31, 2014