THE MECHANISM OF STEREOSELECTIVITY IN THE CYCLOADDITION REACTIONS OF ALPHA-HYDROXY-ORTHO-QUINODIMETHANES WITH THE FUMARATE OF METHYL LACTATE AND MANDELATE

The Diels-Alder cycloaddition reaction of the fumarate of methyl lacta te or methyl mandelate with alpha-hydroxy-ortho-quinodimethane produce s an unexpected exo product with very high asymmetric induction. Exper iments and calculations have been carried out that show that the origi n of the stereoselectivity in these reactions is related to hydrogen b onding between the alpha-hydroxy-o-quinodimethane and the lactate or m andelate group in the dienophile.