1. For general reviews on organic synthesis utilizing imines and theirN-substituted derivatives as electrophiles, see: (a)Comprehensive OrganicSynthesis; Trost, B. M., Fleming, I., Eds.; Pergamon: Oxford, UK, 1991; Vol. 2, pp 893−1109. (b) Bloch, R.Chem. Rev.1998,98, 1407−1438. (c) Enders, D.; Reinhold, U.Tetrahedron: Asymmetry1997,8, 1895−1946. (d) For a recent review on Mannich reactions, see: Arend, M.; Westermann, B.; Risch, N.Angew.Chem.Int. Ed.1998,37, 1044−1070. (e) For a recent review on catalytic enantioselective additions to imines, see: Kobayashi, S.; Ishitani, H.Chem.Rev.1999,99, 1069−1094.