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.
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