Acid–Base Bifunctional Catalysts for the Preparation of Fine Chemicals: Synthesis of Jasminaldehyde

Mechanistic studies of aldol condensations in UiO-66 and UiO-66-NH 2 metal organic frameworks

“…It is commonly known that the jasminaldehyde condensation occurs in the presence of a catalyst [1][2][3][4][5][6]. For the condensation of jasminaldehyde on UiO-66 as catalyst, we propose a mechanism that includes 6 steps ( Figure 5a).…”

“…The main drawbacks of the homogeneous process for the synthesis of jasminaldehyde include the absence of reusability and recycling of the catalyst, environmental pollution due to liquid alkali waste and post reaction work-up of the spent bases [3]. Apart from homogeneous catalysts, various heterogeneous catalysts such as large pore HY and beta zeolites, mesoporous aluminosilicates (Al-MCM-41), amorphous aluminophosphates (AlPO, Na-AlPO) [4], magnesium organosilicates [5], calcined hydrotalcite [3] and metal-organic frameworks [6] have been explored for the synthesis of jasminaldehyde.…”

“…It was proposed that UiO-66-NH 2 acts as a bifunctional catalyst with Lewis acid Zr-sites and Brønsted base -NH 2 sites, rendering it more active and selective towards jasminaldehyde [6]. Furthermore, it was proposed that the Lewis acidic Zr 6 O 4 (OH) 4 secondary building units (SBUs) activate benzaldehyde, while the amino groups on the ligand can activate the aliphatic aldehyde. The co-catalytic role of the amino groups has been assumed to partly explain the increased observed activity, but so far there has been no in depth investigation of the reaction that could support the mechanism proposed on basis of purely experimental data.…”

Layered zeolitic materials: an approach to designing versatile functional solids

“…126 The high accessibility and zeolitic acid strength of ITQ-2 have expanded the possibilities of zeolites for catalytic applications into the field of fine chemicals preparation as demonstrated in our group. 127 For instance, during the preparation of dimethylacetals and tetrahydropyranylation of alcohols and phenols, it was shown that when bulky reactants are involved in the reaction, ITQ-2 exhibited higher activity than large pore zeolites due to the optimal combination of strong and accessible acid centers. 128,129 Acetalization reactions on ITQ-2 conducted very successfully to the synthesis of orange blossom and apple fragrances.…”

129Xenon NMR: Review of recent insights into porous materials

“…It consists in the synthesis of layered zeolite precursors which are subsequently swollen (by exchange with bulky cations) and finally exfoliated using ultra-sounds in order to make the potentially active sites accessible at the external surface. For large reactants, delaminated zeolites show higher activity than conventional large-pore acid zeolites, AlMCM-41 mesoporous solids or amorphous silica-alumina [103].…”