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Please login or sign up for a free trial to access the full content. Method 6: Modification of Nitrogen Functionalities

DOI: 10.1055/sos-SD-017-00353

Döpp, H.; Döpp, D.Science of Synthesis, (200417316.

Triazinamines 379 (R1=2-deoxy-β-d-ribofuranosyl) are benzoylated to give the amides 380 or transformed into (dialkylamino)methylidene derivatives 381 by reactions with form­amide dimethylacetals giving protected 2-azaadenosines used in oligodeoxynucleotide syntheses (Scheme 111).[‌391‌] Treatment of diimidazo[1,2-c:4,5-e][1,2,3]triazines 382 with N-bromosuccinimide under mild conditions cleaves the etheno bridge, and provides another efficient route to 2-azaadenosines 383 (Scheme 111).[‌390‌,‌391‌] Application of the ­normal procedure for the conversion of a hydrazino into an azido group by reaction with nitrous acid fails when the substrate is 4-hydrazino-1,2,3-benzotriazine. Instead ring opening to the diazonium salt occurs even under very mild reaction conditions.[‌356‌] However, 4-azido-1,2,3-benzotriazine (384) is obtained when the hydazide is treated with isopentyl nitrite in glacial acetic acid (Scheme 111).[‌356‌] For thiazolo[2,3:1,6]pyr­ido[2,3-d][1,2,3]triazine derivatives the conversion of the hydrazinyl unit into an azide group by reactions with nitrous acid do take place,[‌374‌] and reactions of 4-hydrazinopyr­ido[3,2:4,5]thieno[3,2-d][1,2,3]triazines,[‌369‌] or 4-hydrazinoimidazo[4,5-d][1,2,3]tri­azines,[‌196‌] with aromatic aldehydes afford the corresponding 4-benzylidenehydrazino-1,2,3-triazines.

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