A. Sera et al., TIN(IV) CHLORIDE CATALYZED HETERO-DIELS-ALDER REACTION OF METHYL 2-OXO-4-PHENYL-3-BUTENOATE WITH STYRENE, Heterocycles, 43(10), 1996, pp. 2205-2214
Hetero-Diels-Alder reactions of methyl 2-oxo-4-phenyl-3-butenoate with
styrene to give dihydropyran derivatives were found to proceed throug
h an exo-selective concerted as well as an ionic stepwise mechanisms c
oncurrently.