Diketones, with 4-aminothiazoles

Salts of 4-aminothiazoles react with chlorovinyl ketone (82) or with /3-diketones (83) at 140°C to yield the thiazoio[3.4-u]pyrimidine derivatives (84) (Scheme 58) (240). 

Simple examples of this strategy, which for the synthesis of thiazoles is known as the Hantzsch synthesis, are shown below the syntheses of 2,4-dimethylthiazole where the heteroatoms are provided by thioacetamide, " and 2-aminothiazole, in which 1,2-dichloroethyl ethyl ether is utilised as a synthon for chloroethanal and the heteroatoms derive from thiourea. " The use of thioureas as the sulfur component with 2-chloroacetamides as the second unit gives rise to 2,4-diaminothiazoles. " Conversion of 1,3-diketones into their 2-phenyliodonium derivatives and reaction of these with thioureas produces 2-amino-5-acylthiazoles. The first step in such ring syntheses is 5-alkylation. " A useful variant is the use of an a-diazo ketone in place of the a-halocarbonyl component. " ... 

Bridgedhead thiazolo[3,2-a]pyrimidines, and their isosteres occupy a unique place in medicinal chemistry due to their wide application as drug and drug-intermediates [7-11]. Several methods are known for synthesis of thiazolo[3,2-a]pyrimidine derivatives, from 2-mercaptopyrimidines and a-halo ketones, and by cyclocondensation of a-aminothiazoles with P-diketones, P-keto aldehydes, and their acetals, P-chlorovinyl ketones and aldehydes. 

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