1. A. K. Shanazarov, N. P. Solov'eva, V. V. Chistyakov, and V. G. Granik, Khim. Geterotsikl Soedin., No. 1, 86 (1991).
2. Ya. F. Freimanis, The Chemistry of Enamino Ketones, Enamino Imines, and Enamino Thiones [in Russian], Zinatne, Riga (1974).
3. H. Meerwein, W. Florian, N. Schön, and G. Stopp, Ann., 641, 1 (1961).
4. F. W. Wehrli and T. Wirtin, Interpretation of Carbon-13 NMR Spectra, Rheine, New York-London (1976), p. 56.
5. J. Müller, Z. Physiol. Chem., 135, 108 (1924).