1. Reviews: (a) ElgueroJ., In Comprehensive Heterocyclic Chemistry II; KatritzkyA.R., and ReesC.W., ScrivenE.F.V., eds, Pergamon Press: Oxford, 1996; Vol. 3, p 1;
2. Vol. 6, p 347, (c) K.Y. Lee, J.M. Kim and J.N. Kim, Tetrahedron Lett. 2003, 44, 6737 and references therein.
3. (a) ElgueroJ., In Comprehensive Heterocyclic Chemistry II; KatritzkyA.R., and ReesC.W., ScrivenE.F.V., eds, Pergamon Press: Oxford, 1996; Vol. 3, p 1;
4. (b) A.N. Kost and I.I. Grandberg, In Advances in Heterocyclic Chemistry, A.R. Katritzky and A. J. Boulton, eds, Academic Press: New York, 1966; Vol. 6, p 347,
5. (c) K.Y. Lee, J.M. Kim and J.N. Kim, Tetrahedron Lett. 2003, 44, 6737 and references therein.