One-Pot Synthesis of 2-Substituted 1H-Isoindole-1,3(2H)-dithiones from Secondary Benzothioamides and Isothiocyanates
摘要:
The reaction of 2,N-dilithiobenzothioamides, generated from readily available secondary benzothioamides and two equivalents of butyllithium, with isothiocyanates, followed by aqueous workup, gives the corresponding N-1,N-2-disubstituted benzene-1,2-dicarbothioamides, which undergo intramolecular attack of one of the thioamide nitrogen on the adjacent thiocarbonyl moiety with loss of primary amines to provide 2-substituted 1H-isoindole-1,3(2H)-dithiones.
Three component reactions of olefins, amines, and sulfur were studied. Thioamidation of styrenes is base-controlled, and 2-phenylethanethioamides and benzothioamides were obtained selectively in the presence of two different bases. This protocol offers a simple and efficient procedure for the synthesis of thioamides.
A new decarboxylative strategy has been developed for the synthesis of thioamides via a three-component reaction involving arylacetic or cinnamic acids, amines and elemental sulfur powder, without the need of a transition metal and an external oxidant.