Electrostatically Enhanced Phosphoric Acids and Their Applications in Brønsted Acid Catalysis

Abstract

Different types of Brønsted acid catalysts are commonly used in a wide variety of organic transformations and are of continuing interest because there is a general need to carry out reactions in a faster and higher yielding manner with greater selectivities. Phosphoric acid derivatives, with their fairly strong acidity and structural flexibility that enables them to be incorporated into rigid organic frameworks, are one of the most efficient and versatile classes of Brønsted acids. Herein, a novel type of electrostatically enhanced phosphoric acids that contain positively charged ion centers are synthesized and studied. The activities of achiral phosphoric acids with alkylated pyridinium ion moieties were examined in a variety of organic transformations. In addition, the activities and enantioselectivities of a series of chiral phosphonium ion tagged phosphoric acids were also evaluated in several different organic reactions. The study of electrostatically enhanced phosphoric acids was found to provide promising avenues for developing novel Brønsted acid catalysts.