Palladium-Catalyzed Cyclization of 1,ω-Dienols: Multiple Ways to Intramolecularly Trap a Carbocation
摘要:
The tandem catalytic cyclization-rearrangement of 1,omega-dien-3-ols by palladium(II) produces different types of products, depending on the structure of starting material. The pinacol rearrangement, benzannulation, and oxy-Cope rearrangement are major pathways of transforming the putative sigma-alkylpalladium carbocation. Turnover of the cyclization is achieved by beta-hydride elimination and reoxidation of palladium with benzoquinone. The overall course of the reaction is very sensitive to small changes in the substrate structure.
Oxidative Cyclization Reactions: Controlling the Course of a Radical Cation-Derived Reaction with the Use of a Second Nucleophile
作者:Alison Redden、Robert J. Perkins、Kevin D. Moeller
DOI:10.1002/anie.201308739
日期:2013.12.2
Construction of new ring systems: Oxidative cyclizations (see picture; RVC=reticulated vitreous carbon) have been conducted that use two separate intramolecular nucleophiles to trap an enol ether‐derived radical cation intermediate. The reactions provide a means for rapidly trapping the radical cation intermediate in a manner that avoids competitive decomposition reactions.
Catalytic Intramolecular Coupling of Ketoalkenes by Allylic C(
<i>sp</i>
<sup>3</sup>
)−H Bond Cleavage: Synthesis of Five‐ and Six‐Membered Carbocyclic Compounds
作者:Tsuyoshi Mita、Masashi Uchiyama、Yoshihiro Sato
DOI:10.1002/adsc.201901533
日期:2020.3.17
In the presence of a catalytic amount of cobalt(II) acetylacetonate/Xantphos in combination with trimethylaluminum, various ketoalkenes underwent an intramolecular cyclization reaction triggered by cleavage of the allylic C(sp3)−H bond, affording carbocyclic compounds with high regio‐ and diastereoselectivity. Mono‐, bi‐, and tricarbocyclic compounds were produced in good yields. One of the products
The anodic oxidation of 1-acetoxy-1,6-heptadiene homologues in acetic acid gave mainly intramolecular cyclization products, cyclohexenyl ketones. The cyclization takes place through the electrophilic attack of the cationic center generated from the enol ester moiety to the double bond.
Intramolecular 1,3-dipolar addition reactions of nitrones were investigated. Four alkenyl nitrones were studied: 2-allyl-, 2-(3-butenyl)-, 2-(4-pentenyl)-, and 2-(9-decenyl)-N-methylcyclohexanimine N-oxides. Among these, 2-(3-butenyl)-N-methylcyclohexanimine N-oxide was found to cyclize most smoothly, giving a perhydroindene derivative as a single regio- and stereoisomer. A perhydroazulene derivative
Direct Regioselective Dehydrogenation of α‐Substituted Cyclic Ketones
作者:Sebastian Armin Schwengers、Gabriela Guillermina Gerosa、Tynchtyk Amatov、Naoki Yasukawa、Sebastian Brunen、Markus Leutzsch、Benjamin Mitschke、Grigory André Shevchenko、Benjamin List
DOI:10.1002/anie.202307081
日期:2023.8.28
A highly regioselective, one-step dehydrogenation of α-substituted cyclicketones in the presence of 2,3-dichlorobenzo-5,6-dicyano-1,4-benzoquinone is described. The reaction proceeds via phosphoric acid-based enol catalysis and provides access to several α-aryl and α-alkyl substituted α,β-unsaturated ketones.