Tetrafluoroboric acid → 5-bromo-2-nitroThiazole

Participants

Reaction Conditions

Reaction Steps

Scheme 3 depicts a method for preparing compounds of formula 1 wherein R1 is ABN-. An aqueous solution consisting of 5-bromo-2-aminothiazole (6) and 20% tetrafluoroboric acid are added to an aqueous slurry of copper powder and sodium nitrite at about 0° C., followed by warming to about 23° C. Standard work-up and purification by radial chromatography afford 5-bromo-2-nitrothiazole 7. Treatment of 7 with triethylamine and ABNH hydrochloride in dimethylsulfoxide at about 60° C. affords 8. Dissolution of 8 in a solvent such as ethyl acetate and treatment with palladium on carbon and hydrogen gas (3 atmospheres) affords aminothiazole 4. The aminothiazoles thus obtained can be treated with a carboxylic acid (HO(═O)C(CR10R11)nR4), propanephosphonic acid cyclic anhydride, and triethylamine in a solvent such as ethyl acetate or dichloromethane to afford compounds of formula 1.

Provenance & Evidence