Salt solutions in different solvents and their effect on the stereoselectivity of products of Diels-Alder reaction

A salt solution prepared in one solvent promotes higher endo products of a Diets-Alder reaction, such as the cyclopentadiene-methyl acrylate reaction, but yields less endo products when prepared in another solvent. The reacti ons of cyclopentactiene with methyl acrylate were carried out in solutions of LiClO4 and LiCl in several organic solvents and water. Aqueous LiClO4. w hich lowers the amount of endo product of the above reaction. enhances it i n solvents such as diethyl ether and ethyl acetate. Similarly, aqueous LiCl . which acts as a rate-promoting agent. reduces the amount of endo products in several organic solvents. The experimental solubility measurements supp ort this change in the characteristics of a salt from salting-in to salting -out in different solvents and vice versa. The dual role of a salt in solve nts is also supported by salting coefficients calculated based on theory. C opyright (C) 2001 John Wiley & Sons, Ltd.