Bovine serum albumin-catalysed cross aldol condensation: Influence of ketone structure

ARDANAZ, SEBASTIÁN M.; BORUCKI, ESTEFANÍA L.; VELEZ RUEDA, ANA J.; PARISI, GUSTAVO; IRIBARREN, ADOLFO M.; IGLESIAS, LUIS E.

PROCESS BIOCHEMISTRY - (Print)

ELSEVIER SCI LTD

Año: 2019 vol. 86 p. 50 - 57

1359-5113

Bovine serum albumin (BSA) catalyses the cross aldol condensation and proved to be catalytically active at mild temperature and in ethanol, a cheap and green solvent, contrasting with the strong or expensive reaction media usually employed for this reaction. We herein report the reaction of a set of ketones (butanone, 3-pentanone, cyclopentanone and cyclohexanone) with benzaldehyde and p-nitrobenzaldehyde which provided high conversions (77?95%) of the corresponding enones (isolated in a range of yields from 19% to 74%). Parameters assayed to achieve these conversion values were solvent, ketone/aldehyde molar ratio and temperature. In this procedure only cyclohexanone gave the bis-enone, by-product of the conventional aldol condensation, in low amount even at high benzaldehyde/cyclohexanone molar excess. Under the assayed conditions null or low ketol amounts were observed, except for the reaction of cyclopentanone and p-nitrobenzaldehyde. Moreover, kinetic data of BSA-catalysed aldol condensation of cyclohexanone and p-nitrobenzaldehyde suggest an ordered bi bi mechanism for enone formation; an enamine mechanism involving residues of the catalytic cavity exhibiting abnormal pKa values is also proposed.