A Highly Selective Aldol Condensation of Cyclopentanone with Valeraldehyde Over Hydrotalcite-type Catalysts

Abstract

The aldol condensation using cyclopentanone with valeraldehyde was conducted at hydrotalcites catalysis. The catalyst was obtained by calcining the hydrotalcite precursor (Mg/Al = 3:1) at 773 K. Its reaction performance was evaluated on the various molar ratios of cyclopentanone to n-valeraldehyde. A good catalytic selectivity of 90 % and a high conversion of 93 % were achieved under mild conditions.

Aldol Condensation of Cyclopentanone with Valeraldehyde Over Metal Oxides

“…Several reactions are catalyzed by homogeneous and heterogeneous bases, including aldol condensation [1][2][3][4] and transesterification for product of biodiesel [5]. Aldol condensation is used for synthesis of various products ranging from basic and specialty chemicals to fragrances, flavours and pharmaceuticals [1][2][3][4][5]. Conventionally aldol condensation is performed using homogeneous catalysts [6,7], such as sodium or potassium hydroxide or Ti(O-t-Bu) 4 as catalysts [7].…”

“…Heterogeneous catalysts could facilitate a more environmentally benign way to produce chemicals, as for example in alkaline earth metal-transition metal oxide in biodiesel production [5], or in aldol condensation due to their easy separation and reuse. Very often heterogeneous base catalysts are also quite cheap, such as aluminophosphate [1] and hydrotalcites [2], active in synthesis of 2-pentylidenecyclopentanone. In this work cross-condensation of valeraldehyde with cyclopentanone was investigated over several heterogeneous catalysts of basic nature, such as Ce-MgO, CaO and Fe-modified CaO and MgO.…”

“…This ketone being the desired product, can further react with another aldehyde forming 2,5-dipentylidenecyclopentanone 7. Cross-aldol condensation of valeraldehyde with cyclopentanone has been very scarcely studied over heterogeneous catalysts [1,2]. The desired product 4, 2-pentylidenecyclopentanone has been synthesized over heterogeneous hydrotalcites as catalysts giving maximally 90% yield using valeraldehyde to cyclopentanone molar ratio of 1:5 at 80 °C after 11 h via slowly adding valeraldehyde into the reactor containing cyclopentanone [2].…”

“…Cross-aldol condensation of valeraldehyde with cyclopentanone has been very scarcely studied over heterogeneous catalysts [1,2]. The desired product 4, 2-pentylidenecyclopentanone has been synthesized over heterogeneous hydrotalcites as catalysts giving maximally 90% yield using valeraldehyde to cyclopentanone molar ratio of 1:5 at 80 °C after 11 h via slowly adding valeraldehyde into the reactor containing cyclopentanone [2]. In another work also an excess of cyclopentanone was used in comparison with valeraldehyde in m-xylene as a solvent at 130 °C under nitrogen [1].…”

“…It should be pointed out here, that as mentioned in the Introduction self-condensation of cyclopentanone forming 2-cyclopentylidene-cyclopentanone, requires presence of strong basicity, thus its contribution to valeraldehyde self-and cross-condensation reactions was considered to be less significant. According to the literature [2] valeraldehyde condensation proceeds via formation of an intermediate 1-hydroxy-2-pentylcyclopentanone 3, which is dehydrated forming the desired product 2-pentylidenecyclopentanone 4. In addition to formation of the desired cross-condensation product, the latter can also be isomerized to 2-pentyl-2-cyclopenten-1-one 5, especially at higher temperature, when this isomer is thermodynamically more stable than the desired product 4 [2].…”