[25] Preparation of thiamine derivatives and analogs

Publisher Summary This chapter discusses the preparation of a number of thiamine homologs and analogs. For the preparation of pyrimidine, 4-amino-5-bromomethyl-2-methylpyrimidine hydrobromide, the methods of Andersag and Grewe are excellent. And for the preparation of the thiazole, 4-methyl-5-(2-hydroxyethyl)thiazole, the method of Buchmann is outstanding. These methods can be applied to the preparation of a number of thiamine homologs and analogs. A practical method for the preparation of the 4,5-dimethyl compound (V: R = CH 3 ) as well as pyrithiamine is presented in the chapter. The intermediate, thiothiamine, formed by the condensation of 4-amino-5-aminomethyl-2-methylpyrimidine, CS 2 , and 3-acetyl-3-chloro-1-propanol is a water-insoluble crystalline compound and is easily converted by oxidation into thiamine in good yield. This method is very useful not only in the laboratory but also in industry and can be applied to the preparation of thiamine homologs and analogs by allowing the various 5-aminomethylpyrimidines to react with various α-chloroketones.