Development of a more efficient catalyst for the redox-neutral organocatalytic mitsunobu reaction by DFT-guided catalyst design

The study of a Mitsunobu reaction is an important topic. Denton and co-workers first reported a novel (2-hydroxybenzyl)diphenylphosphine oxide for realizing the catalytic Mitsunobu reaction via a five-membered phosphonium species. However, it is still worth investigating how to improve catalysts with higher efficiency. Guided by computational and experimental studies, we designed a new type of biphenyl-based phosphine oxide that would form a six-membered phosphonium species as a key intermediate to trigger the catalytic Mitsunobu reaction with a lower barrier of the rate-determining step (30.3 kcal/mol). DFT calculations revealed that only trans dehydration was participated in our catalytic progress and a strong π-π interaction and small spatial constraint of TS-V were crucial for high behavior. This readily accessible, highly stable, easily recyclable and efficient catalyst would boost the catalytic Mitsunobu reaction.