Palladium-Catalyzed α-Ketocyclopropanation of Norbornenes with Propargyl Acetates
作者:Yuta Tanioka、Naofumi Tsukada
DOI:10.1021/jo500357f
日期:2014.6.6
reacted with norbornene in the presence of a catalytic amount of tetrakis(tripheylphosphine)palladium to give cyclopropylketones. The reaction proceeded with high stereoselectivity, affording a single stereoisomer. The reaction of various substituted norbornenes gave the corresponding cyclopropanes in moderate to good yields.
Norbornene as well as its 5,6-disubstituted derivatives and oxa-norbornene undergoes a novel cyclopropanation with propargyl alcohol in methanol containig cationic (η5-cyclopentadienyl)tris(acetonitrile)ruthenium complexes as catalysts to give exo-3-acetyltricyclooctane derivatives. Cyclopentadienylruthenium catalysts having an electron-withdrawing substituent on the Cp ligand exhibited the highest activity and the cyclopropanation proceeded even at −20 °C. On the basis of a deuterium labeling experiment, a reaction mechanism involving a ruthenacycle intermediate is proposed.
降冰片烯及其 5,6-二取代衍生物和氧杂降冰片烯在甲醇中与丙炔醇发生了一种新的环丙烷化反应,该反应以阳离子 (η5- 环戊二烯基) 三(乙腈)钌络合物为催化剂,生成了外-3-乙酰基三环辛烷衍生物。在 Cp 配体上具有一个抽电子取代基的环戊二烯基钌催化剂表现出最高的活性,即使在 -20 °C 下也能进行环丙烷化反应。在氘标记实验的基础上,提出了涉及钌环中间体的反应机理。
One-Step Synthesis of Oxodimethylenemethane−Transition Metal Complexes and Palladium-Catalyzed Cycloaddition Reaction
Some alkyl allyl carbonates and an allylammonium chloride bearing (1-(butyloxy)ethyl)oxy group at the 2-position of the allyl group were synthesized and successfully transformed to oxodimethylenemethane-palladium and -platinum complexes in one step by mixing with a transition metal-(0) and triphenylphosphine. On the basis of the confirmation of vinyl ether formation by H-1 NMR, the generation of oxodimethylenemethane complexes was rationalized to occur through abstraction of the beta-hydrogen on the acetal carbon by an alkoxide ion which was generated from the allyl carbonate upon oxidative addition of the transition metal. The palladium-catalyzed cycloaddition of the acetonylidene group to strained olefins also proceeded successfully by using these alkyl allyl carbonates.
Palladium-catalyzed reactions of ketone .alpha.-carbonates with norbornenes. An unusual cyclopropanation
In the presence of a palladium(0) catalyst, ketone alpha-carbonates react with norbornene to give a cyclopropane derivative via an oxa-pi-allylpalladium intermediate.
Synthesis and chemistry of some tricyclo[4.2.1.02,5]nonane derivatives