Thiazolo-v-triazol-5 6 -ones

Fusion of s-triazole and 4-thiazolidinone rings can be effected in two possible ways, as exemplified by thiazolo[3,2-f ]-s-triazole-5(6//)-one (83) and thiazolo[2,3-c]-.v-triazoIe-5(6//)-one (85). Only scanty work on these condensed thiazolidinone systems is available, although a considerable amount of work on their thiazole counterpart has been reported. 

Reaction of 91 and 92 with 88 furnishes the arylidene products 89 [81S635 84ZN(B)824 871JC(B)216], whereas the condensation of92a with cyanoacetic acid hydrazide yields the parent bicyclic product 93 (84JHC1885). Arylidene product 89 is presumed to have been obtained via the intermediate 5-benzylidene derivative of 91 and 92 formed by the addition of the active methylene in 91 and 92 to the activated double bond of benzylidene malononitrile with concomitant elimination of malononi-trile, which subsequently adds to the activated double bond of the interme- 

The synthesis of thiazolo[3,2-a]pyrimidin-3(2//)-ones has also been accomplished by two routes. The first, commonly followed, is one in which a 

The thione 119, on reaction with chloroacetic acid, gives a mixture of the cyclized product 120 as well as the uncyclized acid 121, the former being 

Thiones 123 react with chloroacetic acid in the presence of anhydrous sodium acetate in acetic acid and acetic anhydride to give a cyclized product for which structure 124 has been assigned (82MI1). The cyclized product could be isomeric structure 125. The same workers similarly obtained a product formulated as 126 from the reaction of the thione 123 (n = 6) with chloroacetic acid (81M12). Compound 126 reacts with aromatic aldehyde to furnish the arylidene product 127 which is also obtained from the reaction of thione 123 (n = 6), chloroacetic acid, and aldehydes as well as from the condensation reaction of thiazolidinone 124 (n = 6) 

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