Synthesis of enaminones with stationary stereochemistry

Five enaminones 4a-e derived from the reaction of 2,4,4-trimethyl-2-oxazoli ne anion with ethyl acetate, ethyl benzoate, ethyl cyclohexanoate, ethyl he xanoate and ethyl p-methyl benzoate, respectively, were obtained and charac terized by C-13-NMR, H-1-NMR, FTIR, and mass spectral analysis. The enamino nes 4a and 4b were also analysed by X-ray diffraction. Enaminone 4a crystal lized in the monoclinic P2(1)/n space group with a = 9.1450(20) Angstrom, b = 10.5150(20) Angstrom, c = 9.5670 (20) Angstrom, beta = 106.21(30)degrees , Z = 4. Enaminone 4b crystallized in the monoclinic P2(1)/c space group wi th a I 16.0520(30) Iq, b = 26.0460(50) A, c = 12.3520 (20) Angstrom, beta = 111.900(30)degrees, Z = 4. All five enaminones were found to have an exten sive pi electron delocalization and to have the same configuration where th e double bond is trapped by an internal hydrogen bond between the NH and th e C=O.