3- Alkyl-5-acetamidoisothiazoles, nitrosation

Under alkaline conditions, alkyl nitrites nitrosate imidazoles which possess a free NH group in the 4-position (70AHC(12)103). Nitrosation of 3,5-dimethylpyrazole gives the 4-diazonium salt by further reaction of the nitroso compound with more NO". 5-Pyrazolinones are often nitrosated readily at the 4-position. 3-Alkyl-5-acetamidoisothiazoles undergo 4-nitrosation. 

Alkyl-5-acetamidoisothiazoles are nitrosated at the 4-position by nitrosylsulfuric acid (78JOC4154). Isothiazoles are sulfonated at the 4-position using either oleum or sulfur trioxide <72AHQ14)1). 

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