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17.5.2.2.1 Method 1: Photolysis Reaction of Azidopyridines with Nucleophiles

DOI: 10.1055/sos-SD-017-01473

Herr, R. J.Science of Synthesis, (200417948.

Photolysis reactions of azidopyridines have been shown to provide 1,3-diazepines (Scheme 19). Reisinger and co-workers showed that irradiation of 2-azidopyridine (62), which is in equilibrium with the fused tetrazole 63, forms a fleeting nitrene species which inserts intramolecularly to provide an intermediate cyclic carbodiimide. In situ trapping of this intermediate with nucleophiles provides 2-substituted 1,3-diazepines as either 1H- or 5H-tautomers, depending on the nucleophile and on the substitution around the pyridine substrate.[‌72‌‌74‌] When simple alcohols are used as nucleophiles, 1H-1,3-products 64 predominate, whereas the use of secondary amine nucleophiles leads to 5H-1,3-products 65 in most cases. Another research team has shown that 6-chloropyridin-2-amines may be diazotized and photolyzed with alcohol and amine substrates to provide 2,7-disubstituted 5H-1,3-diazepines in good yields.[‌75‌] 2,4-Disubstituted 3-azidopyridines 66 may also be irradiated in the presence of sodium methoxide to provide 4-methoxy-5H-1,3-diazepines 68 via intermediate 67 in moderate yields.[‌76‌]

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