Practical large-scale synthesis of 3,4-isopropylidenedioxypyrrolidine hydrotosylate: Atom economical self-hydrogenolysis of a crystalline borane-benzylamine adduct

An efficient four-step sequence has been developed for the synthesis of 3,4-isopropylidenedioxypyrrolidine hydrotosylate starting from inexpensive N-benzyhnaleimide. This approach features a novel N-debenzylation procedure that utilizes the corresponding borane-benzylamine complex as an internal hydrogen-transfer source. This palladium-catalyzed tandem protonolysis/hydrogenolysis allows cleavage of the borane-amine adduct and debenzylation in a single operation.