Synthesis 2008(24): 4012-4018  
DOI: 10.1055/s-0028-1083253
PAPER
© Georg Thieme Verlag Stuttgart ˙ New York

The BF3×OEt2-Assisted Conversion of Nitriles into Thioamides with Lawesson’s Reagent

Michael Nagla,1, Claudia Panuschkab,1, Andrea Bartab, Walther Schmid*a
a Institute of Organic Chemistry, University of Vienna, Währingerstr. 38, 1090 Vienna, Austria
Fax: +43(1)42779521; e-Mail: walther.schmid@univie.ac.at;
b Max F. Perutz Laboratories, Department of Medical Biochemistry, Medical University of Vienna, Dr. Bohrgasse 9, 1030 Vienna, Austria
Further Information

Publication History

Received 17 June 2008
Publication Date:
01 December 2008 (online)

Abstract

A method for the thiolysis of nitriles by applying Lawesson­’s reagent and facilitated by the addition of boron trifluor­ide-diethyl ether complex is reported. The method opens an easy access to primary thioamides. Aromatic, benzylic, and aliphatic nitriles were converted into the corresponding thioamides in high to quantitative yields (even in unfavorable cases, e.g., ortho-substituted benzonitriles). The reaction was performed in 1,2-dimethoxyethane-tetrahydrofuran or toluene-diethyl ether solvent mixtures at 20-50 ˚C, and exhibited considerable selectivity in the case of multifunctional nitrile substrates, such as cyanomethyl N-acetylphenyl­alaninate, benzoylacetonitrile, 4-cyanobenzamide, 4-acetyl­-benzonitrile, or pent-3-enenitrile.

1

These authors contributed equally.

18

NMR spectroscopic data of 4-cyanothiobenzamide: ¹H NMR (400 MHz, CDCl3): δ = 7.21 (s, CSNH), 7.70 (d, J = 8.4 Hz, 2 H, H2, H6), 7.76 (s, CSNH), 7.93 (d, J = 8.5 Hz, 2 H, H3, H5). ¹³C NMR (400 MHz, CDCl3): δ = 115.5 (s, CCN), 118.3 (s, CN), 127.8 (d, CHCCSNH2), 132.7 (d, CHCCN), 143.3 (s, CCSNH2), 201.0 (s, CSNH2).