Lewis Base Activation of Lewis Acids: Catalytic, Enantioselective Addition of Silyl Ketene Acetals to Aldehydes
作者:Scott E. Denmark、Gregory L. Beutner、Thomas Wynn、Martin D. Eastgate
DOI:10.1021/ja047339w
日期:2005.3.1
The concept of Lewisbase activation of Lewisacids has been reduced to practice for catalysis of the aldolreaction of silyl ketene acetals and silyl dienol ethers with aldehydes. The weakly acidic species, silicon tetrachloride (SiCl4), can be activated by binding of a strongly Lewis basic chiral phosphoramide, leading to in situ formation of a chiral Lewisacid. This species has proven to be a competent
Copper(I)‐Catalyzed Asymmetric Conjugate 1,6‐, 1,8‐, and 1,10‐Borylation
作者:Chang‐Yun Shi、Jungmin Eun、Timothy R. Newhouse、Liang Yin
DOI:10.1002/anie.202016081
日期:2021.4.19
Catalytic asymmetric remote conjugate borylation is challenging as the control of regioselectivity is not trivial, the electrophilicity of remote sites is extenuated, and the remote asymmetric induction away from the carbonyl group is difficult. Herein, catalytic asymmetric conjugate 1,6‐, 1,8‐ and 1,10‐borylation was developed with excellent regioselectivity, which delivered α‐chiral boronates in moderate
Use of 1,3-Dioxin-4-ones and Related Compounds in Synthesis. XLIV. Asymmetric Aldol Reaction of 4-Trimethylsiloxy-6-methylene-1,3-dioxines: Use of Tartaric Acid-Derived (Acyloxy)borane Complex as the Catalyst.
A novel enantioselective synthesis of 1, 3-dioxin-4-ones having a 2-hydroxylated alkyl group at the 6-position has been accomplished by chiral tartaric acid-derived acylborane-mediated aldol condensation of the silyl enol ether derived from 6-methyl-derivatives of 1, 3-dioxin-4-one with achiral aldehydes.
Nonlinear effects and auto-induction in the asymmetric aldol condensation of synthetic equivalents of acetoacetic esters
作者:Rosaria Villano、Margherita De Rosa、Concetta Salerno、Annunziata Soriente、Arrigo Scettri
DOI:10.1016/s0957-4166(02)00539-6
日期:2002.9
(+)-NLEs, have been detected in the Ti(IV)/BINOL complex-mediated catalytic asymmetric aldol reaction of three different masked acetoacetate esters. The use of a different procedure for the catalyst preparation disclosed the occurrence of aldol condensation of Chan's diene through an auto-inductive process.
In situ IR spectroscopy and transmetalation experiments confirm a postulated catalytic cycle. The metalloenolate 1 describes the active intermediate in the aldol reaction catalyzed by [CuF2 (S)-tol-binap}] (see reaction scheme). (S)-tol-binap=(S)-(-)-2,2'-bis(di-p-tolylphosphanyl)-1,1'-binaphthyl.