oxa-[4+2] cycloaddition reaction promoted by a thioxanthylium photoredox catalyst under irradiation with green light has been developed. The reaction of ortho-quinone methides with styrenes smoothly affords the desired cycloadducts. Especially styrenes bearing electron-donating groups are efficiently transformed in this reaction. This method represents a sustainable way to carry out oxa-[4+2] cycloaddition
ortho-Quinone methides are useful transient synthetic intermediates in organic synthesis. These species are most often generated in situ by the acid- or base-mediated transformation of phenols that have been pre-functionalized at a benzylic position, or by biomimetic oxidation of the corresponding ortho-alkylphenols with metal oxidants or transition-metal complexes. Here we describe a method for the
Highly Regio‐, Diastereo‐, and Enantioselective Synthesis of Tetrahydroazepines and Benzo[
<i>b</i>
]oxepines through Palladium‐Catalyzed [4+3] Cycloaddition Reactions
作者:Barry M. Trost、Zhijun Zuo
DOI:10.1002/anie.201911537
日期:2020.1.13
A novel Pd0 -catalyzed asymmetric [4+3] annulation reaction of two readily accessible starting materials has been developed for building seven-membered heterocyclic architectures. The potential [3+2] side pathway could be suppressed though fine tuning of the conditions. A broad scope of cycloaddition donors and acceptors participated in the transformation with excellent chemo-, regio-, diastereo-,
<i>N</i>-Heterocyclic Carbene-Catalyzed [4 + 2] Cyclization of Saturated Carboxylic Acid with <i>o</i>-Quinone Methides through in Situ Activation: Enantioselective Synthesis of Dihydrocoumarins
作者:Yuanfeng Wang、Jian Pan、Jingjiao Dong、Chenxia Yu、Tuanjie Li、Xiang-Shan Wang、Shide Shen、Changsheng Yao
DOI:10.1021/acs.joc.6b02444
日期:2017.2.3
An N-heterocyclic carbene (NHC)-catalyzed formal [4 + 2] synthesis of dihydrocoumarins was realized from saturatedcarboxylicacids and o-quinone methides via an in situactivationstrategy. This protocol results in excellent diastereoselectivity and enantioselectivity and good yields and uses readily available and inexpensive starting materials.
Asymmetric Catalytic [4+5] Annulation of
<i>ortho</i>
‐Quinone Methides with Vinylethylene Carbonates and its Extension to Stereoselective Tandem Rearrangement
作者:Xian‐Tao An、Ji‐Yuan Du、Zhi‐Long Jia、Qing Zhang、Ke‐Yin Yu、Yi‐Zhou Zhang、Xian‐He Zhao、Ran Fang、Chun‐An Fan
DOI:10.1002/chem.201904903
日期:2020.3.23
this designed [4+5] annulation, an unprecedented silica gel-promoted tandem rearrangement reaction featuring a unique asymmetric aromatic Claisen rearrangement is explored at roomtemperature, offering a new method for asymmetric construction of all-carbon quaternary stereocenters embedded in chiral functionalized homoallylic alcohols.