Reactions of Thioacetamide Derivatives with Sulfonyl Azides: An Approach to Active‐Methylene N‐Sulfonylacetamidines

Reactions of functionalized [CN, CO2Et, C(O)NHR, C(S)NR1R2] derivatives of thiomalonic acid and 2-arylthioacetamides with sulfonyl azides were shown to give active-methylene N-sulfonylamidines in 62–98 % yields. Various procedures for the reactions, including the use of pyridine, boiling ethanol, and water, or running the reactions in the absence of a base and solvent at 80 °C, were carried out and compared. The solvent-free variant was the best in terms of yield, and also because it does not require the use of an excess of the toxic and hazardous azides. The reaction was shown to tolerate electron-withdrawing substituents such as carbonyl, cyano, and aryl groups at the C-2 position. The presence of alkyl and phenyl groups on the nitrogen atom of the thioacetamide fragment, and the presence of substituents on the sulfonyl group were also tolerated. Thus, an efficient solvent-free, catalyst-free, and base-free synthetic approach for the synthesis of N-sulfonylmalonacetamidines and 2-arylacetamidines was found.