Stereoselective synthesis of analogs of natural isoprenoids based on the reaction of alkyl 4-dialkoxyphosphoryl-3-methylbut-2-enoates with aldehydes in ionic liquids and in an imidazolium salt—benzene system
作者:S. G. Zlotin、G. V. Kryshtal、G. M. Zhdankina、P. A. Belyakov、E. P. Serebryakov
DOI:10.1023/b:rucb.0000035653.43049.35
日期:2004.3
Condensation of alkyl 4-dialkoxyphosphoryl-3-methylbut-2-enoates with a number of aldehydes under the Homer-Emmons reaction conditions in 1-butyl-3-methylimidazolium hexafluorophosphate and tetrafluoroborate and in 1-butyl-3-methylimidazolium bromide-benzene and 1-butyl-2,3-dimethylimidazolium hexafluorophosphate-benzene systems was studied. The E/Z-stereoisomer ratio of the olefination products for the reaction carried out in ionic liquids was 3 : 1, which corresponds to the values attained previously in the KOH-benzene-(Bu4NBr)-N-n (cat.) system. Quantum-chemical calculations were used to determine the averaged radii (r(0)) of the [(Bu4N)-N-n] and substituted imidazolium cations by means of the Gaussian 98 program package. The stereoselectivity of olefination in the KOH-PhH-phasetransfer catalyst system decreases with a decrease in the r(0) value for the catalyst cation. The possibility of recovery and reuse of ionic liquids is demonstrated.
Stereospecific synthesis of conjugated dienic esters and ketones
作者:M. V. Mavrov、N. A. Urdaneta、Nguyen Kong Hao、�. P. Serebkyakov