Synthesis of dihydrocarbazoles via (4+2) annulation of donor-acceptor cyclopropanes to indoles
摘要:
Dihydrocarbazoles were synthesized through a novel [4+2] annulation of donor-acceptor cyclopropanes (DACs) to indoles. This reaction was performed in ethanol by using para-toluenesulfonic acid as catalyst. Mechanism of this reaction might involve the following three steps: (i) an electrophilic ring-opening reaction of the DACs with indoles, in which C3 position of indole acts as a nucleophilic site, (ii) an intramolecular dehydration induced ring-closing reaction occurs that offers a spiro intermediate, and (iii) a following 1,2-migration which leading to a dihydrocarbazole scaffold. Otherwise, dihydroisoindole can also be constructed by replacing the indole component with pyrrole as nucleophile. (C) 2015 Elsevier Ltd. All rights reserved.
An effective method to synthesize α‐functionalized furan and pyrrole derivatives was developed using 2‐alkoxy‐2,3‐dihydrofurans as modular precursors. This protocol featured a previously unreported tandem nucleophilic substitution/heteroaromatization reaction. Nucleophiles such as indole, α‐oxoketene dithioacetal, trimethoxybenzene, and dimethoxynaphthalene can react readily with 2‐alkoxy‐2,3‐dihydrofurans
Sc(OTf)<sub>3</sub> Catalyzed [4 + 2]-Annulation Reaction between Electron-Rich Phenols and Donor–Acceptor Cyclopropanes: Synthesis of Polysubstituted Dihydronaphthols
作者:Yong-Chun Luo、He Ma、Xiu-Qin Hu、Peng-Fei Xu
DOI:10.1021/acs.joc.6b02566
日期:2017.1.20
phenols, a Sc(OTf)3 catalyzed cascade [4 + 2]-annulation reaction was developed for the direct synthesis of polysubstituted dihydronaphthols from phenols. In this reaction, the structure of products is dominated by the directing effect of the substituent groups on phenols. Meanwhile, a one-pot Friedel–Crafts alkylation/oxidative cyclization reaction was also developed for the synthesis of spiro-fused
Chalcogen Bonding Catalysis of the Cloke‐Wilson Rearrangement
作者:Xinglong Yuan、Lintao Bao、Zhiguo Zhao、Yao Wang
DOI:10.1002/chem.202203822
日期:——
Conventionally, the Cloke-Wilson rearrangement is facilitated by strong Lewis acids, Brønsted acids and Lewis bases. Herein, a chalcogen bonding catalysis approach to the Cloke-Wilson rearrangement is established, affording dihydrofurans with moderate to good yields.