1. (a) Baylis, A. B.; Hillman, M. E. D. German Patent 2,155,113. Chem. Abstr. 1972, 77, 34,174q. However, a similar reaction had been reported as a patent in 1967 by Japanese scientists. (b) Toyo Rayon Co., Ltd. French Patent 1,506,132. Chem. Abstr. 1969, 70, 19613u. (c) Morita, K.; Suzuki, Z.; Hirose, H. Bull. Chem. Soc. Jpn. 1968, 41, 2815.
2. Basavaiah, D.; Rao, P. D.; Hyma, R. S. Tetrahedron 1996, 52, 8001 and references cited therein.
3. (a) Burgess, K., Jennings, L. D. J. Org. Chem. 1990, 55, 1138. (b) Basavaiah, D.; Dharma Rao, P. Synth. Commun. 1994, 24, 917. (c) Adam, W.; Hoch, U.; Saha-Moller, C. R.; Schreier, P. Angew. Chem., Int. Ed. Engl. 1993, 32, 1737.
4. Compound (±)-5a in Table 1: Culvenor, C. C.; Geissman, T. A. J. Am. Chem. Soc. 1961, 83, 1647.
5. The absolute configurations of the optically active compounds were assumed from the specific rotations by comparison with those of the similar compounds cited above in Ref. 3a.