In the Chichibabin reaction

The Chichibabin reaction for the synthesis of indolizines has been revisited and some variations have been proposed. The modified benzotriazole 168 reacted with substituted pyridines 167 in refluxing dimethylformamide (DMF). The indolizine 169 bears a triazole moiety that proved useful for the construction of benzo-annulated indolizines <2000JOC8059>. Also, cyclic iminium ylides like 170 can be used in the Chichibabin reaction. Their solvolysis produced the corresponding indolizinones 171 (Scheme 40). 

In general, the 1,3-diazoles do not react by nucleophilic substitution, although imidazole can participate in the Chichibabin reaction with substitution at C-2 the position of substitution is eqmvalent to that noted with pyridine (see Section 11.4.1). Nucleophilic species that are strong bases, like... 

Bipyridyls are by-products in the Chichibabin reaction. The dimerization of methyl-pyridinium salts has been patented, as it provides a route to the important herbicide paraquat (69USP3478042). Pyridine may undergo reduction in the presence of other nftetals as mentioned in Sections 2.05.4.7.5 and 2.05.4.7.6. 

Figure 8-19. In the Chichibabin reaction a pyridine reacts with sodium amide in a solvent such as yV,yV-dimethylaminobenzene. The initial product is a dihydropyridine, which is oxidised to give a 2-aminopyridine. The attack of the amide nucleophile occurs predominantly at the 2-position of the pyridine.

Kametani, T., Nemoto, H. Syntheses of heterocyclic compounds. CCLIII. Mechanism of the formation of an abnormal product in the Chichibabin reaction of quinoline. Chem. Pharm. Bull. (Tokyo) 1968,16, 1696-1699. 

Dimerization is well known to be a side reaction in the Chichibabin reaction (78RCR1042). In fact, dimerization can be the only product with certain alkylpyridines (79USP4177349 81USP4267335). Under normal Chichibabin conditions, heating a heterogeneous mixture of sodium amide in a hydrocarbon at atmospheric pressure with a branched chain alkylpyridine leads to... 

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