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Synlett 2005(10): 1535-1538  
DOI: 10.1055/s-2005-869839
LETTER
© Georg Thieme Verlag Stuttgart · New York

A Novel One-Pot Solvent-Free, Triethylamine-Assisted, Selenium-Catalyzed Synthesis of Thiocarbamates from Nitroarenes, Carbon Monoxide, and Thiols

Xiaopeng Zhanga,b, Shiwei Lu*a,b
a National Engineering Research Center for Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 161 Zhongshan Road, Dalian 116011, Liaoning, P. R. China
b Graduate School of Chinese Academy of Sciences, Beijing, P. R. China
Fax: +86(411)83698749; e-Mail: lusw@dicp.ac.cn;
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Publication History

Received 15 March 2005
Publication Date:
12 May 2005 (online)

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Abstract

A novel one-pot solvent-free synthesis of a series of thiocarbamates is reported. Nitroarenes, carbon monoxide, and thiols are the starting materials, with cheap element selenium as catalyst; this method offers a simple access to thiocarbamates mostly in moderate to good yields. The selenium catalyst can be easily recovered and recycled.

Key words

thiocarbamates - carbon monoxide - selenium - thiols - carbonylation - nitroarenes

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Preparation of dithiocarbonic acid S , S ′-dibenzyl ester. To a 100 mL stainless steel autoclave, selenium (10 mmol), phenyl-methanethiol (20 mmol), and triethylamine (10 mmol) were added. The reactor was then sealed, flushed three times with carbon monoxide. Then carbon monoxide was introduced to the autoclave (0.8 MPa) and the reactor was placed in the oil bath preheated to 60 °C with stirring. After 10 h, the apparatus was cooled to room temperature and degassed. The pure dithiocarbonic acid S,S′-dibenzyl ester was obtained by column chromatography (silica gel, petroleum ether) in 96% yield. Recrystallization from ethanol gave colorless needles; mp 69-70 ° C (lit. [22] mp 45-46 °C); 1H NMR (400 MHz, CDCl3): δ = 7.31-7.21 (m, 10 H), 3.58 (s, 4 H).

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Preparation of phenyl-thiocarbamic acid S-benzyl ester(2i) by the reaction of aniline with dithiocarbonic acid S , S ′-dibenzyl ester. To a 100 mL stainless steel autoclave, dithiocarbonic acid S,S′-dibenzyl ester (5 mmol), aniline (5 mmol) and chloroform (5 mL) were added. The reactor was then sealed and flushed three times with carbon monoxide. Then carbon monoxide was introduced to the autoclave (0.8 MPa, approximately 30-35 mmol), and the reactor was placed in the oil bath preheated to 60 °C with stirring. After 10 h, the apparatus was cooled to room temperature and degassed. The pure phenyl-thiocarbamic acid S-benzyl ester (2i) was obtained by column chromatography (silica gel, petroleum-chloroform, 1:1) in 86% yield. Recrystallization from chloroform-petroleum ether gave to colorless needles; mp 97-98 °C (lit. [25] mp 96-97 °C); 1H NMR (400 MHz, CDCl3): δ = 7.40-7.08 (m, 11 H), 4.22 (s, 2 H).

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Typical experimental procedure is as follows (Table 1, entry 2): To a 100 mL stainless steel autoclave, selenium (0.5 mmol), nitrobenzene (10 mmol), propane-1-thiol (10 mmol), and triethylamine (5 mmol) were added. The reactor was then sealed, flushed three times with carbon monoxide. Then carbon monoxide was introduced to the autoclave (0.8 MPa, approximately 30-35 mmol), and the reactor was placed in the oil bath preheated to 60 °C with stirring. After 10 h, the apparatus was cooled to room temperature and degassed. The crude product was then dissolved in THF and stirred for 30 min to precipitate selenium. The catalyst was then recovered by filtration. The filtrate was concentrated. The pure phenyl-thiocarbamic acid S-propyl ester (2b) was obtained either by column chromatography (silica gel, chloroform-petroleum ether, 2:1) in 84% yield or by recrystallization from light petroleum ether in 72% yield as colorless needles; mp 83-84 °C (lit. [27] mp 84 °C); 1H NMR (400 MHz, CDCl3): δ = 7.42-7.07 (m, 6 H), 2.95 (t, J = 8.0 Hz, 2 H), 1.68 (sextet, J = 8.0 Hz, 2 H), 0.99 (t, J = 8.0 Hz, 3 H).