2- mercapto-5-thiazolone

The most commonly used method for the preparation of fused thiazoles involves the reaction of a-mercapto N-heterocyclic compounds of type (138) with an a-halocarbonyl compound or ester to give S-alkylated intermediates (139) which can be dehydrated to (140). When R2 is alkoxy, thiazolones (141) are formed (Hantzsch synthesis). Strong dehydrating agents are necessary to cyclize aldehydes and ketones (139) to fused thiazoles. The method has been used to prepare (dihydro) imidazo[2,l-6]thiazoIes and thiazolo[3,2- ]-s-triazoles (80JHC1321, 78JHC401, 82IJC(B)243). 

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