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13.29.1.1.2.6.2 Variation 2: 1,2,3,4-Thiatriazol-5-amines from Isothiocyanates and Trimethylsilyl Azide

DOI: 10.1055/sos-SD-013-01396

Begtrup, M.Science of Synthesis, (200413841.

Trimethylsilyl azide also reacts with isothiocyanates to give thiatriazol-5-amines 11 (Scheme 17).[‌40‌] The yields with this reagent are approximately the same as with hydrazoic acid but the reaction is much faster (2 days) and avoids working with the more hazardous hydrazoic acid. The first step in this reaction is claimed to be the cycloaddition of trimethylsilyl azide to isothiocyanate leading to a 1:1 cycloadduct which in aqueous methanolic solution decomposes into the thiatriazole and hexamethyldisiloxane. A much lower reactivity between isothiocyanate and trimethylsilyl azide in dry benzene was reported,[‌51‌] stressing the need for a hydroxylic solvent in the thiatriazole forming process. Trimethylsilyl azide can be prepared in situ. Thus N-phenyl-1,2,3,4-thiatriazol-5-amine (11, R1=Ph) was obtained in a single step from chlorotrimethylsilane, sodium azide, and phenyl isothiocyanate in dimethylformamide (83%).[‌52‌]

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