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Electrophilic benzylation of the pyridine ring. Action of benzyl chlorides on 2‐amino and 2‐benzylaminopyridine
Author(s) -
Kowalski Piotr
Publication year - 1993
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570300220
Subject(s) - chemistry , pyridine , pyridinium , ring (chemistry) , electrophile , medicinal chemistry , solvent , benzyl chloride , hydrochloride , organic chemistry , catalysis
The reaction of 2‐aminopyridine as well as 2‐benzylaminopyridine hydrochloride with benzyl chlorides used in molar ratio of 1:2 and 1:1 respectively and carried out at 250° leads via 2‐benzylamino‐5‐benzylpyri‐dines to 2‐amino‐5‐benzylpyridines as the final products. The formation of 2‐benzylamino‐5‐benzylpyridines did not occur in the direct C ‐benzylation reaction of the 2‐benzylaminopyridine ring with the use of benzyl chloride. Its formation takes place via the intermediate state of 2‐( N,N ‐dibenzylamino)pyridinium and 1‐benzyl‐2‐benzylaminopyridinium chlorides for which the solvent separated ion‐molecule form is proposed. Interaction of the ingredients of the intermediate state i.e. , benzyl cation and 2‐benzylaminopyridine, leads in an electrophilic mechanism to the formation of 2‐benzylamino‐5‐benzylpyridine hydrochlorides. Thermolysis of the aminomethylene bond in 2‐benzylamino‐5‐benzylpyridine hydrochlorides leads to the final 2‐amino‐5‐benzylpyridines.