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Synthesis of pyrido[1,2‐ a ]benzimidazoles by cyclizative condensation of 2‐halopyridines and 1,2‐benzenediamines. Scope and mechanism of the reaction
Author(s) -
Sundberg Richard J.,
Ellis James E.
Publication year - 1982
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.5570190326
Subject(s) - chemistry , pyridine , condensation , benzene , medicinal chemistry , imidazole , nucleophile , ring (chemistry) , nucleophilic substitution , nitro , scope (computer science) , stereochemistry , catalysis , organic chemistry , physics , alkyl , computer science , thermodynamics , programming language
The scope and mechanism of acid‐catalyzed cyclizative condensation of 2‐halopyridines with 1,2‐benzene‐diamines has been explored. The reaction requires a 2‐halopyridine which is activated toward nucleophilic substitution. Evidence in favor of a mechanism involving pyridine ring opening is presented. Of three substituted 1,2‐benzenediamines which were examined, the 4‐nitro compound gave a single cyclization product whereas 4‐chloro and 4‐methy 1‐derivatives gave isomeric mixtures. The structure of the product from 2‐chloro‐5‐nitropyridine and 4‐nitro‐1,2‐benzenediamine is shown to be 2,8‐dinitropyrido[1,2‐ a ]benz‐imidazole.