HETEROCYCLIC SULFUR COMPOUNDS-LXXXV Steric Effects in the Reaction of Primary Amines upon 3,1-Benzothiazine-4-thiones

The reaction of primary amines with 3,1-benzothiazine-4-thiones is known to be a good synthesis of 3H-quinazoline-4-thiones. This paper shows that, depending on the steric characteristics of the amine group and of the substituent carried in position 2 by the benzothiazinethione, 4-imino-4H-3,1-benzothiazines can be obtained. Preparation and identification of the 3H-quinazoline-4-thiones and of their isomers, 4-imino-4H-3,1-benzothiazines are described. In acidic ethanol it has been found difficult to isomerize the above mentioned imines into the corresponding thiones and ethyl-2-(thioaroylamino)benzoates have been obtained.