Development of effective Lewis acids for the catalytic Diels–Alder reaction of α,β-unsaturated lactones with cyclopentadiene
作者:Hikaru Yanai、Arata Takahashi、Takeo Taguchi
DOI:10.1016/j.tetlet.2007.02.131
日期:2007.4
We found that 'Tf2CH2 + Me3Al' systems are effective catalytic systems for the DA reaction of less reactive alpha,beta-unsaturated lactone derivatives, compared to alpha,beta,-unsaturated ester derivatives, with cyclopentadiene. Mononuclear aluminum methide complex, Tf2CHAlMe2, as an active species is formed in these catalytic systems. Effects of lactone ring-size on the reactivity and stereoselectivity were also examined. By expanding ring-size, reactivity of alpha,beta-unsaturated lactones reduced but endo-selectivity notably increased. (c) 2007 Elsevier Ltd. All rights reserved.