HIGHLY STEREOCONTROLLED PROTON TRANSFER IN AN ENAMMONIUM-IMINIUM REARRANGEMENT. MECHANISM OF THE STEREOSELECTIVE DEOXYGENATION OF 6-ARYL-6-HYDROXY-1,2,3,5,6,10b-HEXAHYDROPYRROLOISOQUINOLINES WITH BORANE-THF IN TRIFLUOROACETIC ACID.

Article abstract of DOI:10.1016/S0040-4039(00)80682-6

Either diastereomer of 2 or 10 is deoxygenated with BH3-THF/CF3CO2H to give mainly the trans product, 3b or 11b.The process involes a key enammonium-iminium rearrangement in which there is almost exclusive proton delivery from a single face.