- 作者: Tsung-Hsun Chuang and Jim-Min Fang
- 中文摘要:
Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, R.O.C.
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, whereas 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 ZnCl2 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 corresponding 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, whereas 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 incoming electrophiles and the dipole-dipole interactions of the cyano or carboxylate groups, might interplay to give different stereoselectivities in these reaction systems.
201-206 Total Synthesis of Kaempferol and Methylated Kaempferol - 英文摘要: --
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