Synthesis in the Isocamphane Series, XVI. The Regioselectivity of Some Lewis Acids in the Catalyzed Diels-Alder-Reaction of Cyclopentadiene and Mesityloxide

Article abstract of DOI:10.1007/BF00899682

The regioselectivity of 9 Lewis acids in the catalyzed Diels-Alder-reaction of cyclopentadiene and mesityloxide is described and the endo:exo-ratio of 1a and 1b determined by quantitative HPLC- and 1H-NMR-measurements.The reaction mixture of 1a + 1b normally contains more of the endo epimer 1a, e.g. 3:1 for 1a:1b, and is therefore in agreement with the endo rule, only TiCl4 favors the exo epimer 1b. - Keywords: Diels-Alder reaction; Endo:exo ratio; Endo rule; Lewis acids; Regioselectivity