Cinchona Alkaloid-Lewis Acid Catalyst Systems for Enantioselective Ketene−Aldehyde Cycloadditions
摘要:
Asymmetric cinchona alkaloid-catalyzed acid chloride-aldehyde cyclocondensation (AAC) reactions afford enantioenriched 4-substituted and 3,4-disubstituted beta-lactones with near perfect absolute and relative stereocontrol. These reactions are characterized by the operational simplicity derived from using commercially available or easily obtained (one-step) reaction catalysts and in situ ketene generation from acid chlorides. The range of aldehyde substrates that serve as effective AAC substrates include sterically hindered aldehydes such as cyclohexanecarboxaldehyde and pivaldehyde.
Catalyzed acyl halidealdehyde cyclocondensations. New insights into the design of catalytic cross aldol reactions
作者:Scott G. Nelson、Zhonghui Wan、Timothy J. Peelen、Keith L. Spencer
DOI:10.1016/s0040-4039(99)01308-8
日期:1999.9
quantities (2.5–20 mol%) of Al(SbF6)3 catalyze the di(isopropyl)ethylamine-mediated cyclocondensation of various acylhalides and enolizable aldehydes to afford β-lactones in good yields (58–93%). These reactions are discussed as a strategy for executing chemo- and regiospecific catalyzed cross aldol reactions.
Catalytic Asymmetric Acyl Halide−Aldehyde Cyclocondensation Reactions of Substituted Ketenes
作者:Scott G. Nelson、Cheng Zhu、Xiaoqiang Shen
DOI:10.1021/ja0391208
日期:2004.1.1
Catalyticasymmetricacylhalide-aldehydecyclocondensation (AAC) reactions of alkyl-substituted ketenes with structurally diverse aldehydes provide cis-disubstituted beta-lactones with high enantioselectivity. The AAC reactions utilize a novel Al(III)-triamine catalyst in which the metal's dynamic coordination geometry leads to a highly selective catalyst complex. These AAC reactions represent a functional
Cinchona Alkaloid-Lewis Acid Catalyst Systems for Enantioselective Ketene−Aldehyde Cycloadditions
作者:Cheng Zhu、Xiaoqiang Shen、Scott G. Nelson
DOI:10.1021/ja0492900
日期:2004.5.1
Asymmetric cinchona alkaloid-catalyzed acid chloride-aldehyde cyclocondensation (AAC) reactions afford enantioenriched 4-substituted and 3,4-disubstituted beta-lactones with near perfect absolute and relative stereocontrol. These reactions are characterized by the operational simplicity derived from using commercially available or easily obtained (one-step) reaction catalysts and in situ ketene generation from acid chlorides. The range of aldehyde substrates that serve as effective AAC substrates include sterically hindered aldehydes such as cyclohexanecarboxaldehyde and pivaldehyde.