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4726177 
Journal Article 
Carbocation Catalysis: Oxa-Diels-Alder Reactions of Unactivated Aldehydes and Simple Dienes 
El Remaily, MAbdElAAliAli; Naidu, VR; Ni, S; Franzen, J 
2015 
Yes 
European Journal of Organic Chemistry
ISSN: 1434-193X
EISSN: 1099-0690 
30 
6610-6614 
WOS:000363339600005 
The versatility of the trityl cation (TrBF4) as a highly efficient Lewis acid organocatalyst is demonstrated in the oxa-Diels-Alder reaction of various unactivated aromatic and aliphatic aldehydes and simple unactivated dienes, such as isoprene and 2,3-dimethylbutadiene. The transformation proceeds smoothly to give 3,6-dihydropyrane adducts in high to moderate yields with catalyst loadings down to 1.0 mol-% under mild reaction conditions. In contrast to most previously reported strategies, this protocol does not require substrate functional group activation, neither by electron-deficient aldehydes (2-oxo aldehydes) or electron-rich dienes (methoxy or amino-butadiene). 
Carbocations; Trityl ion; Cycloaddition; Organocatalysis