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A Conformational Study of Cyclohexane‐1,3,5‐tricarbonitrile Derivatives
Author(s) -
Chuang TsungHsun,
Fang JimMin
Publication year - 2001
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.200100032
Subject(s) - chemistry , cyclohexane , cis–trans isomerism , electrophile , steric effects , medicinal chemistry , stereochemistry , bromide , cyclopentane , phenyl group , catalysis , organic chemistry , halogen , alkyl
Abstract Cyclohexane‐1,3,5‐tricarbonitrile reached equilibrium having 1,3‐ cis ‐1,5‐ cis and 1,3‐ cis ‐1,5‐trans isomers in a ratio of 3:7. The cis, cis ‐isomer preferred the conformation with three equatorial cyano groups, where as the cis, trans ‐isomer displayed two cyano groups on equatorial positions and another cyano group on axial position. Condensation of cis, cis ‐cyclohexane‐1,3,5‐tricarbonitrile with L‐( S )‐valinol by the catalysis of ZnCl 2 in refluxing 1,2‐dichlorobenzene afforded two isomeric cyclohexane‐1,3,5‐trioxazolines in favor of the 1,3‐ cis ‐1,5‐trans isomer. Metalation of cis, cis ‐cyclohexane‐1,3,5‐tricarbonitrile, followed by alkylations with dimethyl sulfate, benzyl bromide or allyl bromide, gave the cor responding trialkylation products with predominance of 1,3‐ cis ‐1,5‐trans isomers. The cis, trans ‐isomer showed two cyano groups on axial positions and another cyano group on equatorial position, where as the cis, cis ‐isomer exhibited three axial cyano groups. Treatment of trimethyl cis, cis ‐cyclohexane‐1,3,5‐tricarboxylate with lithium diisopropylamide and dimethyl sulfate afforded mainly the trimethyl ester of Kemp's triacid, which showed three axial carboxylate groups. Two competitive factors, i.e. the steric effect of in coming electrophiles and the dipole‐dipole inter actions of the cyano or carboxylate groups, might inter play to give different stereoselectivities in these reaction systems.