Construction of Vicinal Quaternary Centers via Iridium-Catalyzed Asymmetric Allenylic Alkylation of Racemic Tertiary Alcohols
作者:Mayuko Isomura、David A. Petrone、Erick M. Carreira
DOI:10.1021/jacs.1c00609
日期:2021.3.10
Enantioselective bond formation between stericallyhinderedfragments to furnish acyclic products with vicinal quaternary centers is a formidable challenge. We report a solution that involves cocatalysis between a chiral Ir–(phosphoramidite,olefin) complex and La(OTf)3. This robust catalytic system effects highly enantioconvergent and regioselective alkylation of racemic tertiary α-allenyl alcohols
在空间位阻片段之间形成对映选择性键以提供具有邻位四元中心的无环产物是一项艰巨的挑战。我们报告了一种解决方案,该解决方案涉及手性 Ir–(亚磷酰胺、烯烃)配合物和 La (OTf) 3之间的共催化. 这种强大的催化系统可实现外消旋叔 α-烯醇与四取代甲硅烷基乙烯酮缩醛的高度对映收敛和区域选择性烷基化。该转化对两种反应组分均显示出广泛的官能团耐受性,并允许以良好的收率和出色的对映选择性有效生成 β-烯丙酯产物。此外,通过一系列立体选择性金属催化的官能化反应,利用丙二烯和酯官能度来提升产品的结构复杂性。
A Catalytic Amount of Titanium Tetrahalide as Promoter for the Addition Reaction of Silyl Ketene Acetals to Imines
作者:Makoto Shimizu、Kouji Kume、Tamotsu Fujisawa
DOI:10.1246/cl.1996.545
日期:1996.7
In the presence of a catalytic amount of TiBr4 or TiI4, the reaction of silylketeneacetals with imines smoothly proceeds to give the corresponding β-amino esters in high yield with high anti-sele...
1,2-<i>syn-</i>Selective and Enantioselective Michael Reactions of Acyclic Enones with a Propionate-Derived Nucleophile Catalyzed by Oxazaborolidinone
作者:Toshiro Harada、Toyonao Yamauchi、Shinya Adachi
DOI:10.1055/s-2005-872227
日期:——
1b is demonstrated to be an effective catalyst for the stereoselective Michael reaction of simple acyclicenones with propionate-derived silyl ketene acetals. The reaction affords the corresponding Michael adducts with two contiguous asymmetric centers with high syn selectivity and enantioselectivity.
Lithium perchlorate catalyzed conjugate addition of o-silylated ketene acetals to hindered α,β-unsaturated carbonyl compounds at atmospheric pressure
作者:Paul A. Grieco、R.J. Cooke、Kenneth J. Henry、James M. VanderRoest
DOI:10.1016/s0040-4039(00)92276-7
日期:1991.1
O-Silylated ketene acetals undergo 1,4 conjugate addition to hindered α,β-unsaturated carbonyl systems at atmospheric pressure in the presence of lithium perchlorate.
Iminium salts generated by the oxidation of amino ketene silyl acetals underwent a facile Mannichreaction with another ketene silyl acetal to give aspartic acid derivatives in good yields. The dia...