Synthesis of novel pyridothienopyrimidines, pyridothienopyrimidothiazines,pyridothienopyrimidobenzthiazoles and triazolopyridothienopyrimidines

The reaction of 3-amino-4,6-dimethylthieno[2,3-b]pyridine-2-carboxamide (1a ) or its N-aryl derivatives 1b-d with carbon disulphide gave the pyridothie nopyrimidines 2a-d, whilst when the same reaction was carried out using N-1 -arylidene-3-amino-4,6-dimethylthieno[2,3-b]pyridine-2-carbohydrazides (1e- h), pyridothienothiazine 3 was obtained. Also, refluxing of 1b-d with aceti c anhydride afforded oxazinone derivative 4. Compounds 2a and 2b-d were als o obtained by the treatment of thiazine 3 with ammonium acetate or aromatic amines, respectively. When compound 2a was allowed to react with arylidene malononitriles or ethyl alpha -cyanocinnamate, novel pyrido[3",2":4',5']th ieno[3',2' :4,5]pyrimido[2,1-b][1,3] thiazines 5a-c were obtained. Treatmen t of 2b-d with bromine in acetic acid furnished the disulphide derivatives 6a-c. U.V. irradiation of 2b-d resulted in the formation of pyrido [3",2":4 ',5']thieno[3',2':4,5]pyrimido[2,1-b]benzthiazoles 7a-c. The reaction of 2a -d with some halocarbonyl compounds afforded the corresponding S-substitute d thiopyrido thienopyrimidines 8a-j. Compound 8b was readily cyclized into the corresponding thiazolo[3",2"-a]pyrido[3',2':4,5]thieno[3,2-d]pyrimidine 9 upon treatment with cone, sulphuric acid. Heating of 2a,b with hydrazine hydrate in pyridine afforded the hydrazino derivatives 11a,b. Reaction of ester Sc with hydrazine hydrate in ethanol gave acethydrazide 10. Compounds 10 and 11a,b were used as versatile synthons for other new pyridothienopyr imidines 12-15 as well as [1,2,4] triazolopyridothienopyrimidines 16-19.