Completely OH-Selective FeCl3-Catalyzed Prins Cyclization: Highly Stereoselective Synthesis of 4-OH-Tetrahydropyrans
摘要:
The completely OH-selective Prins cyclization has been realized from the enantioselective ene reaction product. A variety of 4-hydroxyl-tetrahydropyrans were exclusively generated via FeCl3-catalyzed Prins reaction. Excellent stereoselectivities (up to >99:1 dr and >99.5:0.5 er) were obtained for a remarkably broad range of substrates under mild reaction conditions. The control experiments, including NOE effects and O-18-labeling studies, as well as DFT calculations were conducted to provide fundamental insights into the mechanism of the reaction. A different [2 + 2] cycloaddition process was suggested to rationalize the observed OH-selectivity.
Significant counterion effect of the In(III)–pybox complex in highly enantioselective carbonyl-ene reactions of ethyl glyoxylate
作者:Jun-Feng Zhao、Teguh-Budiono W. Tjan、Teck-Peng Loh
DOI:10.1016/j.tetlet.2010.06.066
日期:2010.10
A highly efficient enantioselective carbonyl-ene reaction of ethyl glyoxylate catalyzed by an In(III)-pybox complex, which is designed based on the counterion effect, is reported. Reactions of both aliphatic and aromatic 1,1-disubstituted olefins proceed smoothly to give enantioenriched homoallylic alcohols with excellent yields and enantioselectivities. In addition, electron-withdrawing as well as donating groups on the phenyl ring of alpha-methyl styrenes are tolerated in this reaction. (C) 2010 Elsevier Ltd. All rights reserved.
Enantioselective Carbonyl–Ene Reactions Catalyzed by Chiral Cationic Dirhodium(II,III) Carboxamidates
作者:Xichen Xu、Xiaochen Wang、Yuxiao Liu、Michael P. Doyle
DOI:10.1021/jo5013674
日期:2014.12.19
An enantioselectivecarbonyl–enereaction of glyoxylate esters with 1,1-disubstituted alkenes catalyzed by chiral cationic dirhodium(II,III) carboxamidates is described. The paddlewheel dirhodium(II,III) carboxamidates having one open coordination site at each rhodium smoothly catalyze the carbonyl–enereaction to afford homoallylic alcohol products in good isolated yields with high enantioselectivities
The completely OH-selective Prins cyclization has been realized from the enantioselective ene reaction product. A variety of 4-hydroxyl-tetrahydropyrans were exclusively generated via FeCl3-catalyzed Prins reaction. Excellent stereoselectivities (up to >99:1 dr and >99.5:0.5 er) were obtained for a remarkably broad range of substrates under mild reaction conditions. The control experiments, including NOE effects and O-18-labeling studies, as well as DFT calculations were conducted to provide fundamental insights into the mechanism of the reaction. A different [2 + 2] cycloaddition process was suggested to rationalize the observed OH-selectivity.