2,4-Dibromothiazole 8 is a key intermediate in the synthesis of antifungal agents such as the melithiazoles.

a) Compound 8 cannot be prepared by the bromination of the parent thiazole ring system. By consideration of the intermediates involved rationalize why the 5- position is the site of the first bromination. (3 marks)

b) Fortunately compound 8 is accessible on tonne scale reactions by the following scheme. Provide a mechanism for each of the steps of the sequence. (5 marks)

S La heat + H2N NH2 ENH with aq. HCI Br, -N- excess POBr 98 % yield Br 85 % yield 8