Tertiary Enaminones Research Articles

Nuclear Magnetic Resonance Studies of Anticonvulsant Enaminones

1H nuclear magnetic resonance (NMR) spectra of enaminones were determined and compared to the anticonvulsant activity of the compounds. Although the precise employment of the NMR data to predict anticonvulsant activity of the enaminones could not be established, general inferences were made. The NMR data confirmed that the enaminones existed predominantly in the amino tautomer, and no evidence was found for the imino tautomer. The ketamine form of the enaminones was supported by the observed spin-spin splittings of the NH with the α-protons on certain enaminones. The NH of secondary enaminones was very important in conferring anticonvulsant activity to the enaminones. The peak for the NH proton which could be seen between δ (ppm) 4.50 and 9.70 was present in all of the active enaminones. The tertiary enaminones, which were devoid of the NH proton, were uniformly inactive. It appeared that a combination of steric and electronic effects, lipophilicity, and hydrogen bonding were necessary for the anticonvulsant activity of the enaminones. The cyclic enaminones existed in thetrans-S-transfixed conformation, and the NMR data supported our hypothesis that enantioselectivity is retained in synthesizing enaminones from cyclic, diasteriomeric 1,3-diketones. In addition, the AB system and many unique features were observed in some enaminones. The para, meta, and ortho substituted patterns were observed for monosubstituted phenyl protons, and the NMR patterns for di- and trisubstituted phenyl groups were elucidated.

3-Hydroxypyrroles and 1H-pyrrol-3(2H)-ones. Part 13. Reactions of methoxymethylene Meldrum's acid with 3-hydroxypyrroles, with 3-methoxypyrroles and with other active substrates, and pyrolytic heterocyclisations of the products

Methoxymethylene Meldrum's acid 2 in acetonitrile solution acts as a useful C-electrophile for active substrates such as pyrrole, indole or tertiary enaminones to give substitution products (e.g.5, 6 or 12, respectively). Primary enaminones react exclusively at the nitrogen atom under these conditions. The effect of ring substituents on the regiochemistry of electrophilic substitution of 3-hydroxypyrroles and 3-methoxypyrroles was studied using methoxymethylene Meldrum's acid as the electrophile. Flash vacuum pyrolysis of the Meldrum's acid derivatives obtained in many of these reactions gave access to a range of heterocyclic systems, including the pyridone 48, quinolinedione 43, benzazepinedione 41 and fused pyrones 50, 52and 54.

ChemInform Abstract: INTRAMOLECULAR Cα‐ AND CΓ‐ALKYLATIONS OF TERTIARY ENAMINONES. FACILE ROUTES TO FUNCTIONALIZED INDOLE RING SYSTEMS

AbstractDie aus den Benzylaminderivaten (I) bzw. (V) durch Umsetzung mit dem Cyclohexandion (II) zugänglichen Enaminone (III) bzw. (VII) cyclisieren mit Salzsäure bzw. Silberperchlorat zu Oxoindol‐Derivaten (IV) bzw. (VIII).

INTRAMOLECULAR Cα- AND Cγ-ALKYLATIONS OF TERTIARY ENAMINONES. FACILE ROUTES TO FUNCTIONALIZED INDOLE RING SYSTEMS

Abstract Under the suitably controlled conditions, the tertiary enaminones undergo intramolecular ring formation at Cα and Cγ to give 1-(2-bromo-4,5-methylenedioxybenzyl) tetra (or hexa)hydro-4(or 6)-oxoindoles which can serve as potential precursors to lycoranes.

Use of cyclohexane-1,3-dione derivatives in the preparation of enaminones

Vinylogous esters and acid halides have been compared with respect to their rates of hydrolysis and of reaction with ammonia and amines. Under alkaline conditions the vinylogous esters were hydrolysed faster than the comparable acid halides. Conversely the reaction of the vinylogous acid halides with base to give enaminones was generally faster than that of the esters. Great differences in reaction rates were observed: when tertiary enaminones are being prepared it is very advantageous to use vinylogous acid halides as starting materials.