Pyridinium reaction with alkyl nitrite

Pyridinium salts of type (57) are smoothly converted into iV-substituted pyridones (58) on reaction with pentyl nitrite and sodium methoxide, in an average yield of 64% (Scheme 24). 3-Phenacylpyridinium salts, e.g. (59), react with hydrazine and potassium hydroxide to give 4-alkyl-6-phenylpyridazines, e.g. (60), by a process involving ring-opening, ring-closure, and Wolff-Kishner reduction (Scheme 25). ... 

In 2011, Driver and coworkers synthesized dimebolin by utilizing a ruthenium-catalyzed nitrenoid insertion reaction that they developed (Scheme 16.10) [21]. Azide 49 was readily prepared from 48 by a two-step sequence, consisting of treatment with sodium nitrite and sodium azide, and alkylation of pyridine. Addition of catalytic RuClg hydrate to 49 formed putative ruthenium nitrenoid 50 [22], which then underwent regioselective C-H amination at the C4 position of the pyridinium ion to give y-carbolinium salt 51 in 91% yield. Deprotonation of the N-H group of 51, followed by alkylation with 52, appended the requisite pyridine... 

Primary alkyl amines RNHi can be convertedto alkyl halides by (1) conversion to RNTs2 (p. 447) and treatment of this with I or Br in DMF, or to N(Ts)—NH2 derivatives followed by treatment with NBS under photolysis conditions, (2) diazotization with terr-butyl nitrite and a metal halide such as TiCU in DMF, or (3) the Katritzky pyrylium-pyridinium method (pp. 447,489). Alkyl groups can be cleaved from secondary and tertiary aromatic amines by concentrated HBr in a reaction similar to 10-71, for example,... 

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