Novozym® 435 and Lipozyme® RM IM as Biocatalysts for Benzyl Benzoate Synthesis

With the ever-increasing demand for clean technology in the industrial sector, natural methods, such as enzyme-catalyzed, represent a sustainable alternative to industrial chemical processes. In this context, the synthesis of benzyl benzoate ester using commercial immobilized lipases was evaluated. For this, a kinetic study was carried out to determine the reaction time (24 h) and enzyme concentration (10 wt%). Then, a 22 full factorial design was proposed to evaluate the effect of molar ratio (benzyl alcohol to benzoic anhydride) and temperature on conversion of benzyl benzoate in the presence of tert-butanol as solvent. For the Novozym® 435, maximum conversion (32%) was achieved at 60 ºC, using a molar ratio of 1:5 (alcohol to anhydride). A maximum conversion of 51% was obtained for Lipozyme® RM IM at 40 ºC and the molar ratio of 1:5. The benzyl benzoate showed moderate antimicrobial action against S. aureus (MIC = 0.05 mg μL-1). With the results, the conclusion was that the methodology of design of experiments was adequate for the proposed system and allowed the optimization of the production of benzyl benzoate.

Synthesis of Vinylene-Linked Covalent Organic Frameworks by Monomer-Self-Catalyzed Activation of Knoevenagel Condensation

Reticular chemistry on the basis of thermodynamically controlled linking modes and numerous organic building blocks has constituted versatile crystalline frameworks in molecular-level precision. However, vinylene-linked organic frameworks (COFs) are still quite far from flexible tailoring either in their structures or topologies, due to the lack of monomers with sufficient activities. Herein, we established a strategy to synthesize vinylene-linked COFs via Knoevenagel condensation of a tetratopic monomer 2,2’,6,6’-tetramethyl-4,4’-bipyridine (TMBP) with linear aromatic dialdehydes in a mixed solvent of benzoic anhydride and benzoic acid. Mechanism investigation suggested that the condensation was promoted by a pyridine-self-catalyzed benzoylation upon the cleavage of benzoic anhydride solvent molecules. The layered structures of the resultant COFs were highly crystallized into orthorhombic lattice with vertically aligned AA stacking mode, delivering high surface areas up to 1560 m2 g-1. The pi-extended conjugated skeletons comprising para-bipyridyl units and vinylene linkages endow these COFs with substantial semiconducting properties, releasing visible light-stimulated catalytic activity in water-splitting hydrogen evolution with a rate as high as 3300 μmol g-1 h-1.

Benzoylation of gossypol using benzoyl chloride and benzoic anhydride as acylating agents

To understand deeply the process of acylation of natural polyphenol gossypol, its stepwise benzoylation was performed using benzoyl chloride and benzoic anhydride as acylating agents in the presence of pyridine-N-oxides. The influence of the composition of a reaction mixture on the benzoylation process and reaction products was analyzed by the method of reversed-phase high-performance liquid chromatography. It was established that benzoylation of gossypol leads to the tautomeric transition of the respective fragment from aldehyde to lactol tautomeric form. This transition is most likely due to the breaking of the hydrogen bond C(7)–OHO=C(11) in combination with the displacement of the aldehyde group by the benzoyl fragment from the naphthyl ring plane (in the case of benzoylation of C(7)–OH group); benzoylation of C(6)–OH group is accompanied by the breaking of the hydrogen bond C(6)–OHO–C(7). These changes of configuration significantly facilitate the proton transfer from the C(1)–OH group to oxygen at C(11) followed by the formation of the lactol cycle. The use of benzoyl chloride as an acylating agent in combination with triethylamine and 4-methoxypyridine-N-oxide allows benzoylating gossypol quickly. However, the variety of formed benzoates is quite large because of the similar reactivity of different hydroxyl groups. In the case of benzoic anhydride, the number of isomeric gossypol benzoates remains quite high. Much more esters with higher retention time are accumulated due to a higher degree of benzoylation.

Tuning Texture and Morphology of Mesoporous TiO2 by Non-Hydrolytic Sol-Gel Syntheses

The development of powerful synthetic methodologies is paramount in the design of advanced nanostructured materials. Owing to its remarkable properties and low cost, nanostructured TiO2 is widely investigated for applications such as photocatalysis, energy conversion or energy storage. In this article we report the synthesis of mesoporous TiO2 by three different non-hydrolytic sol-gel routes, and we investigate the influence of the synthetic route and of the presence and nature of the solvent on the structure, texture and morphology of the materials. The first route is the well-known ether route, based on the reaction of TiCl4 with iPr2O. The second and third routes, which have not been previously described for the synthesis of mesoporous TiO2, involve the reaction of Ti(OiPr)4 with stoichiometric amounts of acetophenone and benzoic anhydride, respectively. All materials are characterized by XRD, N2 physisorption and SEM. By playing with the non-hydrolytic route used and the reaction conditions (presence of a solvent, nature of the solvent, calcination), it is possible to tune the morphology and texture of the TiO2. Depending on the reaction conditions, a large variety of mesoporous TiO2 nanostructures could be obtained, resulting from the spontaneous aggregation of TiO2 nanoparticles, either rounded nanoparticles, platelets or nanorods. These nanoparticle networks exhibited a specific surface area up to 250 m2 g−1 before calcination, or up to 110 m2 g−1 after calcination.

Crystal structure of 2,4,6-trimethylbenzoic anhydride

The title compound, C20H22O3, was formed in the reaction between 2,4,6-trimethylbenzoic acid andN,N-diisopropylethylamine in the presence of 1,3-dichloro-1,3-bis(dimethylamino)propenium hydrogen dichloride, and was recrystallized from diethyl ether solution. It is the first exclusively alkyl-substituted benzoic anhydride to have been structurally characterized. The asymmetric unit consists of a half molecule, the other half of which is generated by twofold rotation symmetry; the dihedral angle between the symmetry-related aromatic rings is 54.97 (3)°. The geometric parameters of the aromatic ring are typical of those for 2,4,6-trimethylphenyl substituted groups. The C=O and C—O bond lengths are 1.1934 (12) and 1.3958 (11) Å, respectively, and the angle between these three atoms (O=C—O) is 121.24 (9)°. In the crystal, molecules are linked by weak C—H...O hydrogen bonds and C—H...π interactions. The packing features wavy chains that extend parallel to [001].

Mechanism of Pd-catalyzed acylation/alkenylation of aryl iodide: a DFT study

The detailed mechanism of the Pd(0)-catalyzed cross-coupling of aryl iodide, benzoic anhydride and ethyl acrylate was clarified by theoretical methods.