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Cyclisation of benzils
Author(s) -
Cremlyn Richard J.,
Swinbourne Frederick J.,
Shode Olufemi O.,
Lynch John
Publication year - 1987
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.5570240124
Subject(s) - chemistry , electrophilic substitution , electrophile , chloride , medicinal chemistry , sulfonyl , benzoyl chloride , organic chemistry , catalysis , alkyl
Treatment of several substituted benzils [3,3′‐ and 4,4′‐dimethyl‐; 2,2′‐, 3,3′‐ and 4,4′‐dichloro‐; 3,3′‐dibromo‐; 4‐( N,N ‐dimethylamino)‐] with an excess of chlorosulfonic acid gave the corresponding 3‐chloro‐2‐phenylbenzofuran disulfonyl dichlorides. Disubstitution was confirmed by microanalytical and spectral data for the corresponding bis( N,N ‐dimethylaminsulfonamides). The positions of electrophilic substitution were not confirmed with 3,3′‐dimethyl‐, 2,2′‐ and 3,3′‐dichlorobenzils. With 4,4′‐dichlorobenzil, a smaller amount of chlorosulfonic acid enabled the isolation of 3,6,4′‐trichloro‐2‐phenylbenzofuran‐5‐sulfonyl chloride, which was identified by X‐ray analysis of the N,N ‐dimethylsulfonamide. The cyclisation failed with 3,3′‐dimethoxy‐, and 3,3′‐ and 4,4′‐dinitrobenzils. The results have been interpreted mechanistically.