1. M.E. Garst, J.N. Bonfiglio, D.H. Grudoski and J. Marks, J. Org. Chem., 1980, 45, 2307. 2. T. Gallagher, M. Giles, R.S. Subramanian and M.S. Hadley, J. Chem. Soc., Chem. Commun., 1992,166. S.H.J. Thompson, R.S. Subramanian, J.K. Roberts, M.S. Hadley and T. Gallagher, J. Chem. Soc., Chem. Commun.,1994,933. 3. T. Mukaiyama, K. Banno and K. Narasaka, J. Am. Chem. Soc., 1979, 96, 7503. 4. E. Nakamura, M. Shimizu, I. Kuwajima, J. Sakata, K. Yokoyama and R. Noyori, J. Am. Chem. Soc., 1983, 48, 932. 5. S. Murata, M. Suzuki and R. Noyori, Tetrahedron, 1988, 44, 4259. 6. F. G. Bordwell, T. Gallagher, X. Zhang, J. Am. Chem. Soc., 1991, 113, 3405.