Acid-Catalyzed Intramolecular [2+2] Cycloaddition of Ene-allenones: Facile Access to Bicyclo[<i>n</i>.2.0] Frameworks
作者:Jun-Feng Zhao、Teck-Peng Loh
DOI:10.1002/anie.200902471
日期:2009.9.14
Two plus two equals a bicycle: A highly efficient acid‐catalyzed intramolecular [2+2] cycloaddition of ene‐allenones affords strained bicyclo[n.2.0] frameworks, which contain vicinal all‐carbon quaternary and tertiary centers (see scheme; Tf: trifluoromethanesulfonyl), under mild conditions with excellent yields and chemo‐, regio‐, and diastereoselectivities.
Stereoselective intramolecular acylation of γ′-benzoyloxyphosphine oxides with an internal chlorotrimethylsilane trap: isolation of silylated tetrahedral intermediates
The kinetic products of the intramolecular acylation of γâ²-benzoyloxyphosphine oxides were revealed by conducting the reaction in the presence of an internal trapping agent. A high level of stereocontrol over the formation of both the stereogenic centre α to phosphorus and the hemiacetal centre was observed. The stereochemistry of the products was determined by X-ray crystallography and 1H NMR and the stereoselectivity of the reaction is explained in terms of the known structure and configurational instability of lithiated phosphine oxides.
Construction of Morphan Derivatives by Nitroso-Ene Cyclization: Mechanistic Insight and Total Synthesis of (±)-Kopsone
作者:Li Zhai、Xuechao Tian、Chao Wang、Qi Cui、Wenhua Li、Sha-Hua Huang、Zhi-Xiang Yu、Ran Hong
DOI:10.1002/anie.201706018
日期:2017.9.11
morphan derivatives with good functional‐group tolerance. DFT calculations revealed that the nitroso–ene reaction proceeds in a stepwise manner involving diradical or zwitterionic intermediates. The rate‐determining step is C−N bond formation, followed by a rapid hydrogen‐transfer step with a chair‐conformation transition state. The current approach was also successfully applied in the first total synthesis
Asymmetric Syntheses of 8-Oxabicyclo[3,2,1]octanes: A Cationic Cascade Cyclization
作者:Bin Li、Yu-Jun Zhao、Yin-Chang Lai、Teck-Peng Loh
DOI:10.1002/anie.201202699
日期:2012.8.6
High octane: A novel and practical syntheses of 8‐oxabicyclo[3.2.1]octanes using a cationic cascade cyclization reaction has been developed (see scheme; TIPS=triisopropylsilyl). The diastereomer of the cyclization product isolated depends upon whether the acetal or aldehyde substrate is used.
Iron(III) Chloride/Phenylsilane‐Mediated Cascade Reaction of Allyl Alcohols with Maleimides: Synthesis of Poly‐Substituted γ‐Butyrolactones
作者:Hua Zhang、Xiao‐Yu Zhan、Xu‐Ling Chen、Lei Tang、Shuai He、Zhi‐Chuan Shi、Yu Wang、Ji‐Yu Wang
DOI:10.1002/adsc.201900843
日期:2019.11.5
A iron‐catalyzed free radical cascade reaction of allyl alcohols with N‐substituted maleimides for accessing poly‐substituted γ‐butyrolactones has been developed. In this protocol, various allyl alcohols can open N‐substituted maleimide rings to form allyl ester intermediates, and the allyl ester intermediates can be converted into an allyl ester alkyl radicals and undergo intramolecular free radical