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Ketalizations of aryl ω‐(2‐imidazolyl)alkyl ketones by glycerol and 3‐mercapto‐1,2‐propanediol. synthesis and characterization of cis‐ and trans‐ {2‐aryl‐2‐[ω‐(2‐imidazolyl)alkyl](1,3‐dioxolan‐4‐yl and 1,3‐oxathiolan‐5‐yl)}methanols
Author(s) -
Kim JangWoo,
Davis Frank S.,
Huang LiangFu,
Abdelaal Salma M.,
Upadhyaya Subhash P.,
Lee Jae Jeong,
Bauer Ludwig
Publication year - 1996
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.5570330112
Subject(s) - chemistry , aryl , alkyl , benzoyl chloride , sodium hydride , medicinal chemistry , methyl iodide , hydroxymethyl , alcohol , acetyl chloride , ketone , organic chemistry , catalysis
Aryl 2‐[(2‐imidazolyl)ethyl or 3‐(2‐imidazolyl)propyl]ketones were ketalized by glycerol or 3‐mercapto‐1,2‐propanediol in boiling benzene in the presence of 4‐toluenesulfonic acid to provide the title compounds. The aryl substituents are 4‐chloro‐, 4‐bromo‐, 4‐fluoro‐, or 2,4‐dichlorophenyl. While aryl (2‐imidazolyl)methyl ketones condensed with glycerol to form cis‐ and trans ‐{2‐aryl‐2‐[(2‐imidazolyl)methyl]‐4‐(hydroxymethyl)}‐1,3‐dioxolanes, related condensations with 3‐mercapto‐1,2‐propanediol, under similar, or even more stringent reaction conditions, produced no 1,3‐oxathiolane analogs, with the starting ketones being recovered. Separation and structure determination of these racemic cis and trans isomeric products are described. The structure of these stereoisomers was established by means of 1 H and 13 C nmr correlation and nOe experiments. Selective methylation of the N ‐unsubstituted 2‐imidazolyl alcohols with one equivalent sodium hydride and methyl iodide provided the corresponding N ‐methyl alcohols in excellent yields. With excess benzoyl chloride, N ‐unsubstituted 2‐imidazolyl alcohols were initially converted to O, N ‐dibenzoates from which the N ‐benzoyl group was easily cleaved by ammonium hydroxide in ethanol to provide benzoate esters.