Highly diastereoselective synthesis of enantioenriched anti-α-allyl-β-fluoroamines

A highly diastereoselective synthesis of anti-alpha-allyl-beta-fluoroamines has been developed involving enantioselective alpha-fluorination of aldehydes followed by a diastereoselective Petasis allyl borono-Mannich reaction. The products are obtained generally in good overall yields for the two steps and with drs of 97 : 3-99 : 1 and ees of 86-92%. Selected products were converted to 3-, 5-and 6-membered ring heterocycles, the latter two types incorporating an exo-cyclic fluorine.