使用顺磁性钴(II)卟啉催化剂[Co II (TPP)](TPP=四苯基卟啉)对邻烯丙基羰基-芳基N-芳基磺酰腙进行金属自由基活化,为合成新型8元杂环化合物提供了一种有效且强大的方法烯醇醚。该合成方案通用且实用,能够以高产率合成多种独特的 1 H -2-苯并氧辛。催化环化反应具有优异的化学选择性,具有较高的官能团耐受性,并为合成新的生物活性化合物提供了多种机会。该反应通过钴(III)-卡宾自由基中间体进行,该中间体参与从烯丙基位置到卡宾自由基的分子内氢转移(HAT),然后在钴的配位层中进行近无障碍的自由基反弹步骤。所提出的机制得到了实验观察、密度泛函理论(DFT)计算和自旋捕获实验的支持。
Enantioselective Synthesis of Multifunctionalized 4<i>H</i>-Pyrans via Formal [4 + 2] Annulation Process by Bifunctional Phosphonium Salt Catalysis
作者:Jia-Hong Wu、Jianke Pan、Juan Du、Xiaoxia Wang、Xuemei Wang、Chunhui Jiang、Tianli Wang
DOI:10.1021/acs.orglett.9b04079
日期:2020.1.17
highly enantioselective formal [4 + 2] annulation involving electron-deficient allenes as C2-synthons has been developed under bifunctional phosphonium salt catalysis. With this catalytic protocol, a wide range of synthetically interesting and highly functionalized chiral 4H-pyran derivatives were readily prepared in good yields (up to 99%) with outstanding diastereo- and enantioselectivities (up to
Aerobic Oxidative Dehydrogenation of Ketones to 1,4-Enediones
作者:Bao-Yin Zhao、Xing-Long Zhang、Rui-Li Guo、Meng-Yue Wang、Ya-Ru Gao、Yong-Qiang Wang
DOI:10.1021/acs.orglett.0c04174
日期:2021.2.19
An efficient and unprecedented strategy for the synthesis of 1,4-enediones from saturated ketones has been developed via palladium-catalyzedoxidativedehydrogenation. The protocol employs molecular oxygen as the sole oxidant and represents an atom- and step-economic process. The approach showed broad substrate scope, good functional group tolerance, and complete E-stereoselectivity. The reaction mechanism
Applications of Thermal Activation, Ball-milling and Aqueous Medium in Stereoselective Michael Addition of Nitromethane to Enynones Catalyzed by Chiral Squaramides
作者:Żaneta A. Ignatiuk、Mikołaj J. Janicki、Robert W. Góra、Krzysztof Konieczny、Rafał Kowalczyk
DOI:10.1002/adsc.201801498
日期:2019.3.5
to conjugated en‐ynones was performed through the application of chiral squaramides. Three non‐classical approaches to promote the addition reaction were tested, including activation of the nucleophile by inorganic base in a biphasic aqueous system, thermal activation, and ball‐milling. Hydrogen‐bonding catalysis was effective in all these methods, providing 1,4‐addition products in high yields and
Organocatalytic Enantioselective Friedel-Crafts Alkylation/Lactonization Reaction of Hydroxyindoles with Methyleneoxindoles
作者:Mengjie Xiao、Dengfeng Xu、Weihong Liang、Wenyu Wu、Albert S. C. Chan、Junling Zhao
DOI:10.1002/adsc.201701089
日期:2018.3.1
Functionalization of the indole benzene ring was achieved by using an organocatalyticenantioselectiveFriedel–Crafts alkylation/lactonization reaction of hydroxyindoles with a variety of substituted methyleneoxindoles. This reaction was applicable to indoles substituted with the hydroxy group at different positions of the benzene ring, and the corresponding pyrrolodihydrocoumarins were obtained in
Direct Intramolecular Conjugate Addition of Simple Alkenes to α,β-Unsaturated Carbonyls Catalyzed by Cu(OTf)<sub>2</sub>
作者:Yan Qin、Jian Lv、Sanzhong Luo、Jin-Pei Cheng
DOI:10.1021/ol502373u
日期:2014.10.3
An unprecedented intramolecular conjugate addition of simple alkenes to α,β-unsaturated carbonyl compounds has been developed. A simple Lewis acid such as Cu(OTf)2 was found to effectively catalyze the reaction, and six- and five-membered cyclic products were obtained in moderate to high yields.