Partial asymmetric synthesis in the diels-alder reaction

The Diels-Alder condensation of (?)-dimenthyl fumarate with butadiene followed by reduction of the adduct with LiAlH₄, produced (?)-(1R:2R)-4-cyclohexene-trans-1,2-dimethanol in 1–3% optical purity depending on the temperature used to carry out the reaction. However, when AlCl₃, SnCl₄ or TiCl₄ are used to catalyze the reaction then the condensation occurs at much lower temperatures and the product after reduction with LiA1H₄ has the opposite sign and configuration. Furthermore the optical purity of the product ranges from 27–78% depending on reaction conditions. Parameters such as solvent, temperature and catalyst, as they affect asymmetric syntheses, are discussed.