General procedure for the synthesis of 4-methyl-5-thiazolecarboxaldehyde from 2-amino-4-methylthiazole-5-carboxaldehyde: A solution of tetrahydrofuran (THF, 3 mL) with amine 2 (5 mmol) was slowly added dropwise over a period of 20 min to a solution of tetrahydrofuran (THF, 3 mL) containing tert-butyl nitrite (t-BuONO, 7.5 mmol) and dimethylsulfoxide (DMSO, 0.5 mmol) in a solution of THF (7 mL). The reaction mixture was stirred continuously at 30°C until complete consumption of feedstock 2 was confirmed by thin layer chromatography (TLC) monitoring. Subsequently, the solvent was removed by evaporation and the yield of the low-boiling products was determined by gas chromatography (GC); the high-boiling products were separated and purified by silica gel column chromatography (eluent: hexane/ethyl acetate solvent mixture).
