Rh(II)-binaphthol phosphate catalysts in the enantioselective intramolecular oxonium ylide formation-[3,2] sigmatropic rearrangement of alpha-diazo-beta-ketoesters

The enantioselective intramolecular oxonium ylide formation-[3,2] sigmatropic rearrangement of α-diazo-β-ketoesters 9 using catalytic (1 mol%) dirhodium tetrakisbinaphthol phosphate catalysts 1 and 2 to give benzofuranones 11 in up to 62% e.e. is described. © 2001 Elsevier Science Ltd

Synthesis and NMR spectroscopic studies of novel N-Acetyl-3-hydrazonoalkyl tetramic acids

3-(Hydrazonoethyl) and 3-(hydrazonobutyl) tetramic acids 6 - 11 are prepared by condensation reaction of N,3-diacetyl and N-acetyl-3-butanoyl tetramic acids, 4 and 5, with a variety of 1,2-(bis)-nucleophiles. The structure elucidation and the tautomeric equilibrium of the novel compounds 6-11 have been studied using 1H and 13C NMR spectroscopy

IR, NMR and dielectric characterization of a novel tetramic acid

The structure of the N-acetyl-3-hexanoyl tetramic acid has been elucidated by IR and NMR spectroscopy. The IR spectra showed absorption bands for the CO group of the β-dicarbonyl system CO-CH-CO ↔ C(OH)=C-CO as well as for the carbon-carbon double bond thus verifying the proposed structure. The 1H and 13C NMR spectra confirm the existence of enolic "internal" and "external" tautomers. The interconversion of "internal" tautomers seems to be faster than that of the "external" ones. The Thermally Stimulated Depolarization Currents (TSDC) spectrum in the temperature range 10-340 K revealed the presence of two predominant relaxation mechanisms, which are tentatively discussed in terms of the relaxation of tautomeric transformations under the influence of the applied electric field. © 1999 OPA (Overseas Publishers Association) N.V. Published by license under the Gordon and Breach Science Publishers imprint