Heterocyclic systems containing bridgehead nitrogen atom: Synthesis and evaluation of biological activity of 3-(2'-furyl)-thiazolo[3,2-b]-s-tetrazines and cis-dihydropyrazolo[3',4':4,5]thiazolo[3,2-b]-s-tetrazines

3-(2'-Furyl)-2,3-dihydro-4H-thiazolo[3,2-b]-s-tetrazin-6(7H)-one 2, 3-(2'-furyl)-2,3,6,7-tetrahydro-4H-thiazolo[3,2-b]-s-tetrazine hydrobromide 5 and 6-aryl-3-(2'-furyl)-2,3-dihydro-4H-thiazolo[3,2-6]-s-tetrazine hydrobromides 6 have been synthesised by the reaction of 6-(2'-furyl)-1,4,5,6-tetrahydro-s-tetrazine-3 (2H)-thione 1 with chloracetic acid, 1,2-dibromoethane and alpha-haloketones, respectively. 7-Arylidene-2,3,6,7-tetrahydro-3-(2'-furyl)-4H-thiazolo[3,2-b]-s-tetrazin-6-anes 3 have been prepared either by the condensation of 2 with aldehydes or in a single step by the reaction of 1 with ethyl chloroacetate and aldehydes in the presence of pyridine and piperidine. Condensation of 3 with hydrazines in the presence of anhydrous sodium acetate furnishes 7,8-diaryl-3-(2'-furyl)-2,3-cis-8,8a-tetrahydro-4H-pyrazolo[3',4' :4,5]thiazolo[3',2-b]-s-tetrazines 4. The antibacterial and antifungal activities of some of the compounds have also been evaluated.