(Z)- and (E)-2-Phenyl-4-benzylidene-5(4H))oxazolones as Dienophiles. Improved Selectivity by the Use of Heterogeneous Catalysts

Article abstract of DOI:10.1016/0040-4020(95)00526-E

Silica gel treated with AlEt2Cl or TiCl4 efficiently promotes the reaction of cyclopentadiene with (Z)-2-phenyl-4-benzylidene-5(4H)-oxazolone (1a) with very little Z/E isomerization.Silica gel treated with TiCl4 and ZnCl2 supported on silica gel leads to