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Base‐catalyzed cyclization reactions of 2‐[2‐(2,4‐dimethyl‐3‐oxopentyl)]benzimidazoles with acetic anhydride and its homologs
Author(s) -
Linke Siegfried,
Wünsche Christian
Publication year - 1973
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.5570100310
Subject(s) - acetic anhydride , chemistry , yield (engineering) , steric effects , base (topology) , catalysis , medicinal chemistry , organic chemistry , mathematical analysis , materials science , mathematics , metallurgy
2‐[2‐(2,4‐Dimethyl‐3‐oxopentyl)]benz, imidazoles ( 2‐10 ) were obtained by allowing o ‐phenyl‐enediamines to react with 2,2,4,4‐tetramethyl‐1,3‐cyclobutanedione ( 1 ). When refluxed with acetic anhydride (or sterically unhindered homologs) they cyclize in the presence of base to yield the pyrido[1,2‐α]benzimidazoles ( 16‐21 and 24, 25 ). The 2‐[2‐(2,4‐dimethyl‐3‐oxo‐pentyl) ]imidazolines ( 12 and 14 ) were obtained by reaction of 1,2‐diaminoethane and 1,2‐diaminopropane, respectively, with 1 . When allowed to react with acetic anhydride/base, they gave only N ‐acylated products.