A facile one-pot synthesis of 6,7,8,9-tetrahydrobenzo[4,5] thieno[2,3-d]-1,2,4-triazolo[4,5-a]pyrimidin-5-ones

The reaction of 2-mercapto-6,7,8,9-tetrahydro3H-benzo[4,5]thieno[2,3- d] pyrimidin-4-one or its 2-methylthio derivative with hydrazonoyl halides, in the presence of triethylamine, yielded 6,7,8,9-tetrahydrobenzo[4,5] thieno [2,3- d]-1,2,4-triazolo[4,5-a] pyrimidin-5-ones. The structure of the latter compounds was further confirmed by reaction of 2-mercapto-6,7,8,9-tetrahydro-3H- benzo[4,5] thieno[2,3- d] pyrimidin-4-one with the appropriate active chloromethylenes followed by coupling of the products with benzenediazonium chloride to afford the non-isolable azocoupling products which converted, in situ, to 6,7,8, 9-tetrahydrobenzo[4,5] thieno[2,3- d]-1,2,4-triazolo[4,5- a] pyrimidin- 5- ones. The reaction mechanism was proposed and the products were screened for their biological activity. Some of the newly synthesized compounds had a moderate effect against some bacterial and fungal species.