Diastereoselective and Branched-Aldehyde-Selective Tandem Hydroformylation-Hemiaminal Formation: Synthesis of Functionalized Piperidines and Amino Alcohols.

Starting from readily available allylglycine, a tandem hydroformylation-hemiaminal formation reaction has been developed for the synthesis of chiral functionalized piperidines, with very good diastereoselectivity and branched regioselectivity using Rh/(S,S,S)-BOBPHOS catalysts. Tandem hydroformylation-hemiacetal formation also proceeds with good diastereoselectivity (88:12), with the hemiacetal product being hydrogenated with retention of stereochemistry to give a chiral intermediate used in the synthesis of the new antibiotic nemonoxacin.