Relay Catalysis of Bismuth Trichloride and Byproduct Hydrogen Bromide Enables the Synthesis of Carbazole and Benzo[α]carbazoles from Indoles and α-Bromoacetaldehyde Acetals
using bismuth trichloride as a catalyst. The reaction was triggered by a bismuth trichloride‐catalyzed Friedel‐Crafts alkylation of these two precursors, which provided a tryptaldehyde intermediate that underwent intramolecular olefination to form the final product. Interestingly, the HBr byproduct generated in the upstream step of the reaction catalyzed the following downstream reaction steps, thus
halogen (Cl, Br, and even I), aldehyde, ketone, carboxyl, and cyano. Moreover, the photoredox catalysis with NaI and stoichiometric PPh3 provides also an alternative entry to Cadogan-type reductive amination when o-nitrobiarenes were used.
Visible-Light-Induced Oxidation/[3 + 2] Cycloaddition/Oxidative Aromatization to Construct Benzo[<i>a</i>]carbazoles from 1,2,3,4-Tetrahydronaphthalene and Arylhydrazine Hydrochlorides
作者:Jiaxuan Shen、Nannan Li、Yanjiang Yu、Chunhua Ma
DOI:10.1021/acs.orglett.9b02939
日期:2019.9.6
An efficient synthesis of benzo[a]carbazoles via visible-light-induced tandem oxidation/[3 + 2] cycloaddition/oxidative aromatization reactions was reported. The benzylic C(sp3)-H of tetrahydronaphthalene was activated through visible-light photoredox catalyst with oxygen as the clean oxidant under mild reaction conditions. This protocol proceeds efficiently with broad substrate scope, and the mechanism
endergonic formation of the intermediate complex of nitrobiarenes and PPh3, which corresponds with experimental findings regarding reactiontemperature. The robust synthetic capacity of the photoredox Cadogan reaction systems has been demonstrated by the viable productivity of a broad range of carbazoles and related N-heterocycles with good tolerance of various functionalities.
已发现可见光驱动的光化学卡多根型环化。发现有机 DA 型光敏剂 4CzIPN 是将能量从光子转移到瞬态中间体的有效介质,该中间体打破了卡多根反应中的脱氧壁垒,并使无温和金属的咔唑和相关杂环成为可能。DFT 计算结果表明硝基双芳烃和 PPh 3的中间体复合物的温和吸能形成,这与关于反应温度的实验结果一致。光氧化还原 Cadogan 反应系统的强大合成能力已通过广泛范围的咔唑和相关N-杂环的可行生产力得到证明,这些N-杂环对各种官能团具有良好的耐受性。
Copper-mediated rapid and facile oxidative dehydrogenation of dihydrobenzocarbazoles
作者:Vivek T. Humne、Avinash G. Ulhe
DOI:10.1080/00397911.2020.1731757
日期:2020.4.2
Rapid method for the oxidative dehydrogenation of dihydrobenzocarbazoles has been introduced by using bench scale and commercially available reagent; copper chloride, in excellent yield with easy workup. The scope of the reaction has been studied with broad range of substitutes