Alkyl Acetoacetates Research Articles

Keten intermediates in the uncatalysed alcoholysis of β-keto-esters and related compounds

Uncatalysed alcoholysis of alkyl acetoacetates and malonates occurs via a unimolecular dissociative mechanism involving concerted elimination of alcohol with resultant formation of substituted ketens as reactive intermediates.

Total Synthesis of Pyrrolnitrin. I. Synthesis of 3-Arylpyrrole Derivatives by Knorr's Condensation

Alkyl 3-aryl-5-methyl-4-pyrrolecarboxylate (IIIa-j) and alkyl 2, 5-dimethyl-3-aryl-4-pyrrolecarboxylate (IIIk-m), two kinds of key intermediates for synthesizing pyrrolnitrin (I), were obtained from 2-aminoacetophenones (IV) and alkyl acetoacetate by Knorr's pyrrole synthesis. The mechanism of the pyrrole ringclosure of the above compounds was proposed since alkyl 3-substituted benzoylmethylaminocrotonates (VIII) could be isolated as intermediates presumably because of their difficult cyclization to the corresponding pyrroles ; for which the infrared spectra of nitro and carbonyl group of VIII were discussed.

Electron impact studies. VI. Mass spectra of esters and thioesters. Skeletal rearrangement on electron impact

The mass spectra of representative series of simple alkyl acetoacetates, alkyl acetothioacetates, and some unsaturated esters derived from unsaturated alcohols or phenols are reported and discussed. The fragmentation schemes have been established by high resolution measurements, appropriate metastable ions, and by deuterium and 18O labelling. Many of the spectra show significant skeletal rearrangement fragments arising from either loss of carbon monoxide or carbon dioxide.

Ketovinylation of β-dicarbonyl compounds

The introduction of the ketovinyl group into β-dicarbonyl compounds with only one labile hydrogen proceeds normally, but the presence of two labile hydrogens results in the formation of complex mixtures. Ethyl malonate and ethyl acetoacetate have, however, been successfully ketovinylated. In the former case, α-carbethoxy-δ-keto-β,γ-unsaturated acids are produced in high yield and depending on the conditions of ketovinylation of ethyl acetoacetate either 4-alkyl salicyclic acids or polysubstituted benzene derivatives may be prepared. Further, the ketovinylation products of ethyl malonate and alkyl acetoacetates may be used for the synthesis of either (1) unsaturated aliphatic keto acids or diketones or (2) a variety of α-pyrone derivatives. A mechanism for the ketovinylation of ethyl acetoacetate is proposed and the trans configuration of the ketovinylation products established.

Trans-enolization

The solvent effect on trans-enolization of different keto-enols is discussed. Ultra-violet and infra-red data are presented on keto-enol equilibrium in α-alkyltetronic acids, isopropylidene alkyl malonates, and α-alkyl-substituted alkyl acetoacetates, bromometrical evidence also being produced for the latter compounds. The limitations of Meyer's rule and Eistert and Reiss' hypothesis as to trans-enolization are shown and the general applicability of the relationship K T = EL + E′L′ is demonstrated.