Iminium Carbonic Acid Derivative Salts. XI [1]. Synthesis of N,S-Containing Heterobicycles from N-Protected 2-Methylthio-1,3-thiazinium and 2-Methylthiothiazolium Salts. Part 3. Reaction of N-Protected 2-Methylthio-1,3-thiazinium and 2-Methylthiothiazolium Salts with 3-Amino-2-cyano-3-arylacrylonitriles

Article abstract of DOI:10.1002/jhet.5570330657

N-Boc-protected 2-methylthio-1,3-thiazinium 1 and 2-methylthiothiazolium iodides 2,3 obtained from the corresponding 3,4,5,6-tetrahydro-2H-1,3-thiazine-2-thiones and thiazolidine-2-thiones by the action of methyl iodide were reacted with 3-amino-2-cyano-3-arylacrylonitriles forming the cyclic isothioureas 5-7. The protection group was removed with trifluoroacetic acid whereupon the desired cyclisation to 3,4-dihydro-2H,6H-pyrimido[2,1-b][1,3]thiazines 8a-c, 8a′-c′ and thiazolo[3,2-b]pyrimidines 9a,b, 9a′,b′, 10a,b took place.