Thiourea 2-bromothiazole

Bromothiazole (1) reacts with thiourea in alcohol to yield a mixture of dithiazolyl monosulfide (2) and A-4-thiazoline-2-thione (3) (Scheme 1) (4-6). Treatment of 2-bromo-4-methvlthiazole with potassium hydrogen sulfide in alcohol is reported to result in the formation of bis(4-methyl-2-thiazolylisulfide (7). which probably results from the reaction between the initially formed 2-mercaptothiazole and the initial 2-bromo-4-methylthiazole. 

Now we must put the molecule together again. 2-Bromothiazole is available so lithiation and carbonylation with DMF gives 213 and an aldol (Knoevenagel) reaction with malonic acid gives 214 without a separate decarboxylation step. The best one-carbon electrophile is ethyl formate (HC02Et) and thiourea makes a suitable derivative of 209 for displacement. 

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