Heterocyclic systems containing bridgehead nitrogen atom : Synthesis, stereochemistry and evaluation of biological activity of thiazolo [3 ,2-<i>b</i>]-<i>s</i>-tetrazines and <i>trans</i>-dihydropyrazolo [3',4' :4,5]thiazolo[3,2-<i>b</i>]-<i>s</i>-tetrazines

Abstract

3,3-Diethyl-2<i>H</i>,4<i>H</i>-thiazolo[3,2-<i>b</i>]-<i>s</i>-tetrazin-6(7 <i>H</i>)-one 2, 3,3-diethyl -2<i>H</i>,4H -6, 7 -dihydrothiazolo[3,2-<i>b</i>]-<i>s</i>-tetrazine hydrobromide <b>4</b> and 6-aryl-3, 3-diethyl-2<i>H</i>, 4<i>H</i>-thiazolo[3,2-<i>b</i>]-<i>s</i>-tetrazine hydrobromide <b>5</b> have been synthesised by the reaction of 6,6-diethyl- l, 2, 4, 5-tetrahydro-<i>s</i>-tetrazin-3-thione <b>1</b> with chloroacetic acid, 1,2-dibromoethane and α-haloketones, respectively. 7-Arylidene-3,3-diethyl-2<i>H</i>, 4<i>H</i> -thiazolo[3,2-<i>b</i>]-<i>s</i>-tetrazin-6(7<i>H</i>)-ones <b>3</b> have been prepared either by the condensation of <b>2</b> with aldehyde or in a single step by the reaction of <b>1</b> with ethyl chloroacetate and aldehydes in the presence of pyridine and piperidine. Condensation of <b>3</b> with 2,4-dinitrophenylhydrazine in the presence of anhydrous sodium acetate furnishes 7,8-diaryl-2<i>H</i>, 4<i>H</i> -<i>trans</i>-8,8a dihydropyrazolo [3',4':4,5]thiazolo[3,2,-<i>b</i>]-<i>s</i>-tetrazines <b>6</b>. The antibacterial and antifungal activity of some of the compounds have also been evaluated.