Carbocations as Lewis Acid Catalysts in Diels-Alder and Michael Addition Reactions
作者:Juho Bah、Johan Franzén
DOI:10.1002/chem.201304160
日期:2014.1.20
the carbocation as a highly powerful Lewis acid catalyst for organic reactions. The stable and easily available triphenylmethyl (trityl) cation was found to be a highly efficient catalyst for the Diels–Alder reaction for a range of substrates. Catalyst loadings as low as 500 ppm, excellent yields, and good endo/exo selectivities were achieved. Furthermore, by changing the electronic properties of the
Unsaturated Aldehydes as Alkene Equivalents in the Diels–Alder Reaction
作者:Esben Taarning、Robert Madsen
DOI:10.1002/chem.200800003
日期:2008.6.20
A one-pot procedure is described for using alpha,beta-unsaturated aldehydes as olefin equivalents in the Diels-Alder reaction. The method combines the normal electron demand cycloaddition with aldehyde dienophiles and the rhodium-catalyzed decarbonylation of aldehydes to afford cyclohexenes with no electron-withdrawing substituents. In this way, the aldehyde group serves as a traceless control element
The development of a new method for effecting [4+2] cycloadditions on the surface of chromatographic adsorbents in the absence of solvents that leads to a moderation of the reaction conditions and an increase in selectivity is described.
Carbocation catalysis in confined space: activation of trityl chloride inside the hexameric resorcinarene capsule
作者:Margherita De Rosa、Stefania Gambaro、Annunziata Soriente、Paolo Della Sala、Veronica Iuliano、Carmen Talotta、Carmine Gaeta、Antonio Rescifina、Placido Neri
DOI:10.1039/d2sc02901d
日期:——
capsule. The inner cavity of the capsule can host the trityl carbocation, which catalyses the Diels–Alder reactionbetween dienes and unsaturated aldehydes. Experimental results and in silico calculations show that the hexameric resorcinarene capsule C6 can promote the formation of the trityl carbocation from trityl chloride through the cleavage of the carbon–halogen bond promoted by OH⋯X− hydrogen bonding