학술논문
Investigation of condensation products of aldehydes with acetoacetic ester catalyzed by organic bases: absolute configuration determination by X-ray crystallography and tautomeric equilibria studies by NMR spectroscopy.
Document Type
Article
Source
Subject
*CONDENSATION products (Chemistry)
*ALDEHYDES
*ETHYL acetoacetate
*ORGANIC bases
*X-ray crystallography
*TAUTOMERISM
*NUCLEAR magnetic resonance spectroscopy
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Language
ISSN
0922-6168
Abstract
Two condensation products of aldehydes with acetoacetic ester catalyzed by methylamine or piperidine, 3a and 3b, were unambiguously assigned by single-crystal X-ray diffraction. Their X-ray crystallographic observations in the solid state and the NMR analysis ever-reported in solution phase, which were complementary to each other, were compared for an in-depth study of reliable geometrical or conformational information of poly-substituted β-keto esters 3a- e, and good agreement is observed between them. Furthermore, keto-enol tautomeric equilibriums of β-keto esters 3a- e have also been investigated using NMR spectroscopy. The results indicated that β-keto esters 3a- e exist as a mixture of keto and enol isomers in chloroform solutions when giving sufficient time at room temperature. The equilibriums were on the side of the keto tautomer with the ratio [enol]/[keto] ranging from 0.11 to 0.66. [ABSTRACT FROM AUTHOR]