An Efficient and Convenient Synthesis of Certain 2-Thioxothiazole,2-oxo-1,2-dihydropridine, 2-Oxo-2<i>H</i>-pyran,2,4-diaminothiophene and Pyrazolo[5,1-c][1,2,4]triazine Derivatives Containing Antipyrine Moiety

Abstract

2-Thioxothiazole derivatives 5a-c were prepared by reacting a mixture of 1a-c, CS2/KOH and 4-(2-chloroacetyl)-1, 5-dimethyl-2-phenyl-1 H -pyrazol-3(2 H )-one(3). Reacting 2-cyano-N-(4-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-2 H - pyrazol-4-yl)-2-thioxothiazol-3(2 H )-yl)acetamide (5c) with mercaptoacetic acid, arylidenemalononitriles 8 and (E)- 3-(dimethylamino)-1-(furan-2-yl)prop-2-en-1-one (12) give 4-oxo-4,5-dihydrothiazole 6, 2-oxo-1,2-dihydropyridine 10 and 2-oxo-2 H -pyran 15 respectively. Heating a mixture of 5c, malononitrile and elemental sulfur yield 2,4-diaminothio- phene 19. Coupling of 5c with the diazotized aminopyrazole 20 and aryldiazonium salts 23 give pyrazolo[5,1-c][1,2,4] triazines 22 and arylhydrazones 25 respectively.