“One-Pot” Access to 4<i>H</i>-Chromenes with Formation of a Chiral Quaternary Stereogenic Center by a Highly Enantioselective Iminium-allenamine Involved Oxa-Michael−Aldol Cascade
作者:Chunliang Liu、Xinshuai Zhang、Rui Wang、Wei Wang
DOI:10.1021/ol102096s
日期:2010.11.5
organocatalytic highlyenantioselectivecascade Michael−aldol reaction has been developed in high yields under mild reaction conditions. The “one-pot” process affords an efficient approach to the synthetically and biologically important chiral4H-chromenes bearing a quaternary stereogenic center. The study significantly expands the scope of less explored organocatalytic iminium-allenamine chemistry.
developed, providing various chiral α-monosubstituted α-aminoacidderivatives with excellent results (97-99% yields, 90 to >99% ee). Cyclic N-sulfonyl ketimines were also hydrogenated well to afford chiral amine derivatives with 98-99% yields and 97 to >99% ee. The gram-scale asymmetric hydrogenation was performed well with 85% yield and 99% ee using only 0.2 mol% catalyst.
Phosphine-Catalyzed (4 + 1) Annulation of <i>o</i>-Hydroxyphenyl and <i>o</i>-Aminophenyl Ketones with Allylic Carbonates: Syntheses and Transformations of 3-Hydroxy-2,3-Disubstituted Dihydrobenzofurans and Indolines
作者:Zifeng Qin、Wei Liu、Danyang Wang、Zhengjie He
DOI:10.1021/acs.joc.6b00596
日期:2016.6.3
A phosphine-catalyzed (4 + 1) annulationreaction of o-hydroxyphenyl and o-aminophenyl ketones with ester-modified allylic carbonates has been developed, providing a facile and efficient method to synthesize functionalized 2,3-disubstituted dihydrobenzofurans and indolines. Under mild conditions and in the catalysis of PPh3 (20 mol %), the reactions of o-hydroxyphenyl or o-aminophenyl ketones readily
The First Catalytic Highly Enantioselective Alkylation of Ketimines—A Novel Approach to Optically Active Quaternaryα-Amino Acids
作者:Steen Saaby、Kimitaka Nakama、Mette Alstrup Lie、Rita G. Hazell、Karl Anker Jørgensen
DOI:10.1002/chem.200305302
日期:2003.12.15
anchoring was synthesized and allowed to react with various silylketene acetals in the presence of 5-10 mol % of a chiral Zn(OTf)(2)-(R,R)-Ph-pybox-aqua complex. The corresponding opticallyactive quaternary alpha-amino acid derivatives were obtained in high yields and with enantioselectivities ranging from 34 % up to 95 % ee. The catalyst was studied by (1)H NMR spectroscopy and X-ray crystallography
P<sup>III</sup>-Mediated intramolecular cyclopropanation and metal-free synthesis of cyclopropane-fused heterocycles
作者:Jiayong Zhang、Jiahang Hao、Zhiqiang Huang、Jie Han、Zhengjie He
DOI:10.1039/d0cc04086j
日期:——
A P(NMe2)3-mediated reductive intramolecular cyclopropanation is developed for the first time, which provides facileaccess to a wide variety of cyclopropane-fused heterocycles including chromanes, tetrahydroquinolines, lactones, and lactams. Catalytic hydrogenative ring-expansion of the cyclopropane-fused heterocycles is also elaborated, leading to various structurally important medium-sized heterocycles