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

Abstract

AbstractA salt solution prepared in one solvent promotes higher endo products of a Diels–Alder reaction, such as the cyclopentadiene–methyl acrylate reaction, but yields less endo products when prepared in another solvent. The reactions of cyclopentadiene with methyl acrylate were carried out in solutions of LiClO4 and LiCl in several organic solvents and water. Aqueous LiClO4, which lowers the amount of endo product of the above reaction, enhances it in 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 support 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 solvents is also supported by salting coefficients calculated based on theory. Copyright © 2001 John Wiley & Sons, Ltd.