Rational design of arsine catalysts for arsa-Wittig reaction

Abstract

The catalytic Wittig reaction is widely used for obtaining alkenes; it avoids the generation of stoichiometric amounts of phosphine oxide. The catalytic arsa-Wittig reaction, in which an arsine catalyst is used instead of phosphine, has the advantage of excellent E-selectivity. However, in our recent study, we reported that high temperatures are required for the reaction to proceed due to the low nucleophilicity in arsines. In this study, we prepared cyclic and acyclic arsines with electron-donating and/or sterically open substituents and examined their catalytic activities. The results showed that tris(p-(dimethylamino)phenyl)arsine (5) exhibited high catalytic activity despite being an acyclic arsine; the traditional phosphine-catalyzed Wittig reaction requires a cyclic phosphine catalyst. Under the optimized reaction conditions, the room-temperature arsa-Wittig reaction proceeded with high yield (up to 82%) and excellent E-selectivity (>98%). Further, using 5 as a catalyst, density functional theory calculations were performed to elucidate the mechanism of the arsa-Wittig reaction.