Coordination-Induced Stereocontrol over Carbocations: Asymmetric Reductive Deoxygenation of Racemic Tertiary Alcohols
作者:Mayuko Isomura、David A. Petrone、Erick M. Carreira
DOI:10.1021/jacs.9b00862
日期:2019.3.20
intermediate tertiary carbocations. This approach has been implemented to achieve the first example of enantioselective reductive deoxygenation of tertiaryalcohols. This reduction occurs with high enantio- (up to 96% ee) and regioselectivity (up to >50:1 rr) by applying a novel Hantzsch ester analogue as a convenient hydride source. In-depth mechanistic studies support the involvement of a tertiary carbocation
Synthesis of homopropargyl alcohols via sonochemical Barbier-type reaction
作者:Adam Shih-Yuan Lee、Shu-Fang Chu、Yu-Ting Chang、Shu-Huei Wang
DOI:10.1016/j.tetlet.2003.12.058
日期:2004.2
were synthesized from the reaction mixture of zinc powder, 1,2-diiodoethane, 3-bromo-1-propyne and aldehyde or ketone in anhydrous THF under ultrasound. The homopropargyl alcohols were obtained as the only product in all cases when aldehydes were reacted with 3-bromo-1-propyne under this sonochemical Barbier-type reaction condition. The homopropargyl alcohol was produced as the major product and the
demonstrated a very generalmethod for the preparation of essentially any terminal 2,3-allenol from the corresponding alkynols, which may be easily available from propargylic alcohols by alkylation, or from terminal alkynes by deprotonation and 1,2-addition with aldehydes or ketones, and subsequent base-catalyzed triple-bond migration. We have demonstrated a very generalmethod for the preparation of essentially
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。
Preparation of γ,δ-Unsaturated β-Ketophosphonates from Tertiary α-Allenic Alcohols. The Synthesis of (±)-(<i>E</i>)-α-Atlantone