Selectivity and Catalysis in Ene Reactions of Diethyl Oxomalonate

Article abstract of DOI:10.1021/jo00187a030

Stereoselectivity, regioselectivity, and structural selectivity of the thermal ene reactions of diethyl oxomalonate are strongly determined by steric approach control.For a series of 1-arylcyclopentenes thermal ene reactions only show a small enhancement of rate by electron-donating substituents (ρ = -1.2 +/- 0.2).Lewis acid catalysis is described which allows ene reactions of diethyl oxomalonate under thermally mild conditions.Furthermore, catalysis by SnCl4 profoundly modifies the selectivity of the ene reactions which show a strong enhancement of rate by electron-donating substituents (ρ = -3.9 +/- 0.3) for a series of 1-arylcyclopentenes.Structural selectivity can be dramatically reversed by catalysts since the influence of electronic factors is amplified by Lewis acids, and steric approach control becomes less important.