The BF3×OEt2-AssistedConversion of Nitriles into Thioamides with Lawesson’sReagent

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