通过使用手性Ni II / N,N'-二氧化物络合物作为催化剂,已实现了对β,γ-不饱和α-酮酸酯的烯丙基硼酸的高度对映体选择性形式共轭烯丙基加成。该转化过程通过烯丙基硼化/ oxy-Cope重排序列进行,提供了简便且快速的途径,以中等至良好的收率(65-92%)和出色的ee值(90-99%ee)转化为γ-烯丙基-α-酮酸酯)。1,2-烯丙基化产物的分离提供了对随后oxy-Cope重排反应机理的认识:底物诱导的手性转移和手性Lewis酸加速过程。在实验研究和DFT计算的基础上,提出了一种罕见的船状过渡态模型,作为氧-科普重排过程中高手性转移的起源。
A new ring for your indole: An unprecedented copper‐catalyzed enantioselectiveFriedel–Craftsalkylation/N‐hemiacetalization cascade reaction with indoles and β,γ‐unsaturated α‐ketoesters is reported. This mild strategy provides new access to various synthetically and biologically important 2,3‐dihydro‐1H‐pyrrolo[1,2‐a]indoles in a highlyenantioselective manner.
吲哚的新环:据报道,铜与吲哚和β,γ-不饱和α-酮酸酯发生了前所未有的铜催化对映选择性Friedel-Crafts烷基化/ N-半缩醛化级联反应。这种温和的策略以高度对映选择性的方式为各种合成和生物学上重要的2,3-二氢-1 H-吡咯并[1,2- a ]吲哚提供了新途径。
Neighboring Thioether Participation in Bioinspired Radical Oxidative C(sp<sup>3</sup>)–H α-Oxyamination of Pyruvate Derivatives
A bioinspired radical oxidative α-oxyamination of pyruvate with an oxoammonium salt through multiple-site concerted proton–electron transfer process has been developed, which was facilitated by anchoring the mercapoto chains as a “hopping” site at the γ-position of α-keto esters.
diastereo-, and enantioselective Diels–Alderreaction of β,γ-unsaturated α-ketoesters with (E)-1-phenyl dienes has been accomplished by using a stable and easily available chiral N,N′-dioxide/zinc(II) complex as catalyst. Only one isomer of the corresponding cyclohexenes with three chiral centers was obtained in good to excellent yields with excellent ee values under mild reaction conditions. The configurations
Highly Enantioselective Nickel-Catalyzed Oxa-[3+3]-annulation of Phenols with Benzylidene Pyruvates for Chiral Chromans
作者:Hai Ren、Xiang-Yang Song、Sunewang R. Wang、Lijia Wang、Yong Tang
DOI:10.1021/acs.orglett.8b01442
日期:2018.7.6
Nickel-catalyzed asymmetric annulation of oxygenated phenols and previously challenging 3-aminophenols with β,γ-unsaturated α-ketoesters is described, leading to rapid access to a variety of oxygenated and 7-aminated chromans in excellent yields with excellent diastereoselectivities and enantioselectivities under mild conditions. This method was readily scaled-up to gram scale and applied for a concise