Sulphate tribromide

The reaction of a-aminonitriles and carbon disulphide was stated by Cook and Heilbron to give 5-amino-2-mercaptothiazoles however, they later found that the same reaction with aminoacetonitrile was more complex. When aminoacetonitrile sulphate in ethanolic solution was treated with carbon disulphide, the dithiodicarbamate 9 was formed. Benzylation was then carried out treatment of the resulting ester 10 with phosphorus tribromide with subsequent loss of water gave 5-amino-2-benzylthiothiazole 11 in a quantitative fashion. The rapid reaction was thought to be the first example of the formation of a 5-aminothiazole from an a-aminoamide. 

Methylating agents for phenolic groups are a) diazomethane (the reaction time varies from minutes to 24 hours), b) dimethyl sulphate (DMS) - potassium carbonate in acetone or dimethylformamide (DMF) and c) methyl iodide - potassium carbonate in acetone. For demethylation of a methyl ether group ortho to a methyl ester group boron tribromide is used, while demethylation of a methyl ether para to a methyl ester group is carried out with boron trichloride (see Scheme 8). 

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