Pyridyl nitrous acid

In a much poorer yield, compound (8) was the product from the thermal decomposition of 5-(2-pyridyl)tetrazole (305) at 400°C/10 Torr (78HCA1755). Compound (305) was prepared by treating pyridine-2-carbonitrile with hydrazoic acid. [l,2,3]Triazolo[l,5-a]pyridines are also the products from the treatment of 1-aminoquinolizinium salts (306a) with nitrous acid in a process proceeding via (306b) (69TL1549). 

Indoxyls (140) have been reported to be oxidized under a variety of conditions to indolones (158). However, the literature claims are conflicting. Ruggli claimed to oxidize 2-phenyl-6-nitroindoxyI to the corresponding indolone with nitrous acid, but attempts to repeat this reaction failed.Benzoyl peroxide oxidized 2-(4-aminophenyl)-4,6-dinitroindoxyl to the corresponding indolone, but methyl indoxyl-2-carboxylate to the diindoxyl (141 R = COjMe). Isatogens are reduced under a variety of conditions to a number of different products which include some indolones (158 R = Ph, 4-methoxyphenyl) and indolone hydrates (139 R = COjMe, 2-pyridyl R = H) for a detailed discussion see Section II1,B and Table I. 

Nitro-3-picoline (MI-368) is hydrolyzed on standing to l-(3 -methyl-4 -pyridyl)-3-methyl-4-pyridone and 3-methyl-4-pyridone. 4-Nitropyridine and benzyl bromide give iV-benzyl-3,5-dibromo-4-pyridone (MI-369) in 33% yield. The quaternary salt first formed is hydrolyzed to the 4-pyridone. Oxidation of hydrogen bromide by the nitrous acid product provides the bromine and water. The yield is increased to 71%by the addition of bromine. 3,5-Dibromo-4-chloro-pyridine and benzyl bromide in base also give XII-369. Similarly, 3-methyl-4-nitropyridine and benzyl bromide give W-benzyl-3-bromo-5-methyl-4-... 

Bis-(2-pyridyl)pyridines. An aq. soln. of excess nitrous acid prepared by adding 10%-H2SO4 at 0° to aq. NaNO, covered with ether, 2,6-bis-(2-pyridyl)-3,5-dicarbethoxy-l,4-dihydropyridine added to the upper layer, and allowed to stand overnight at room temp. 2,6-bis-(2-pyridyi)-3,5-dicarbethoxypyridine. Y 80%. F. 2,6-bis-(2-pyridyl)pyridines s. F. H. Case and W. A. Butlc, J. Org. Chem. 26, 4415 (1961). 

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