Study on the preparation and reaction of biheterocyclic thiazolo pyrimidinium-and thiazolo diazepinium-betaines

Abstract

Biheterocyclic thiazolo [3,2-a] pyrimidine and thiazolo [3,2-a][1,3] diazepine reacted with electrophiles to form biheterocyclic betaines. When 3-substituted-6,7-dihydro-5H-thiazolo [3,2-a] pyrimidine and -5,6,7,8-tetrahydro-thiazolo [3,2-a][1,3] diazepine were reacted with isothiocyanates, isocyanates, ketene and carbon disulfide etc. in aprotic media such as acetonitrile and acetone, and corresponding betaines were obtained in good yields. It was also found that these biheterocyclic betaines are dissociated in polar organic solvents depending on temperature. These betaines react also with alkyl halide to give quarternary ammonium salts. New biheterocyclic compounds were prepared by the reaction of 3-substituted6,7-dihydro-5H-thiazolo [3,2-a] pyrimidinium-betaines and -5,6,7,8-tetrahydrothiazolo [3,2-a][1,3] diazepinium-betaines with $\alpha$-halo ketone, $\alpha$-halo ester and $\gamma$-holo keto ester via ring transformation.