Knoevenagel Condensation of Aromatic Aldehydes with Ethyl 4-Chloro-3-oxobutanoate in Ionic Liquids

• Published in: Journal of the Brazilian Chemical Society Vol. 23; no. 5; pp. 825 - 830
• Main Authors: de Paula, Bruno R. S., Zampieri, Davila S., Zukerman-Schpector, Julio, Tiekink, Edward R. T., Rodrigues, Jose Augusto R., Moran, Paulo J. S.
• Format: Journal Article
• Language: English; Portuguese
• Published: SAO PAULO Soc Brasileira Quimica 01.05.2012; Sociedade Brasileira de Química
• Subjects: Chemistry; CHEMISTRY, MULTIDISCIPLINARY; Physical Sciences; Science & Technology; ionic liquid; ACID; MECHANISM; Knoevenagel condensation; ESTERS; ethyl 4-chloro-3-oxobutanoate; ALPHA-METHYLENATION; CATALYST; ethyl (E/Z)-2-chloroacetyl-3-arylpropenoate; SOLVENT
• ISSN: 0103-5053; 1678-4790; 1678-4790
• DOI: 10.1590/S0103-50532012000500006

Knoevenagel condensations of aromatic aldehydes with ethyl 4-chloro-3-oxobutanoate catalyzed by morpholine/acetic acid were carried out in ionic liquids to give ethyl 2-chloroacetyl-3-arylpropenoates in 44-84% yield after 0.5 to 2 h at room temperature (25-28 degrees C). These conditions represent a greener protocol for the Knoevenagel condensation than those using refluxing benzene or toluene as solvent. Aromatic aldehydes having aryl groups 4-chlorophenyl, 4-methoxyphenyl, 2-thiofuranyl, 2-furanyl, phenyl and 3,4-methylenedioxyphenyl gave (E)/(Z) diastereomeric ratios of products from 56/44 to 85/15. The two isomers of each compound were separately isolated and characterized. The structure of the (E)-isomer of ethyl 2-chloroacetyl-3-(3',4' methylenedioxyphenyl) propenoate was determined by X-ray crystallography and an unequivocal methodology of (E)/(Z)-structural analysis by C-13 NMR (nuclear magnetic resonance) is presented.