Diastereoselective synthesis of hexahydropyrrolo[2,1-b]oxazoles by a rhodium-catalyzed hydroformylation/silica-promoted deformylation sequence.

Fleetingly formyl: A new rhodium-catalyzed hydroformylation reaction of N-allyl oxazolidines, carried out under a CO/H(2) atmosphere, followed by a diastereoselective deformylative cyclization affords hexahydropyrrolo[2,1-b]oxazoles in good yields. The reaction proceeds by a unique hydroformylation-deformylation sequence in which the formyl group virtually substitutes for the {CH(2)-O} fragment of the oxazolidine heterocycle.