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

A highly diastereoselective synthesis ofanti-a-allyl-b-fluoroamineshas been developed involving enantioselectivea-fluorination ofaldehydes followed by a diastereoselective Petasis allyl borono-Mannich reaction. The products are obtained generally in goodoverall yields for the two steps and with drs of 97 : 3–99 : 1 and eesof 86–92%. Selected products were converted to 3-, 5- and6-membered ring heterocycles, the latter two types incorporatingan exo-cyclic fluorine.