Development of a robust immobilized organocatalyst for the redox-neutral mitsunobu reaction

A polystyrene-supported version of the Denton catalyst for redox-neutral Mitsunobu reactions, (2-hydroxybenzyl)diphenylphosphine oxide, has been developed and used in catalytic inversion of enantiopure secondary alcohols (21 examples, up to 97% yield and 98% ee) with 2-nitrobenzoic and 2,4-dinitrobenzoic acids. The use in the reaction of alternative pronucleophiles has also been explored (8 successful and 3 unsuccessful examples). The functional resin shows high recyclability (10 cycles, 30 days operation) and can be re-activated by simple treatment with butylamine with further extension of its useful life.