Substituted imidazo[2,1-b]thiazoles from 2-aminothiazoles and α-bromo ketones: efficient preparation and proof of structure

Abstract

The salts formed from α-aminothiazoles and α-bromo ketones (RCOCH2Br) have been basified, and the products converted into amides. Examination of the amides established that they are 2-acylimino-2,3-dihydrothiazoles rather than 2-acylaminothiazoles. Thus the α-bromo ketones attack the endo-N of the 2-aminothiazoles, and the imidazo[2,1-b]thiazoles obtained by cyclising the salts have the substituent (R) of the bromo ketone at position 6. Efficient procedures have been developed for preparing a range of imidazo[2,1-b]thiazoles.Related reactions of 2-aminothiazoles, with an α-bromo aldehyde and with ethyl bromoacetate, have been studied.