2,4'-Di-O-methylnorsekikaic acid

A series of Brønsted acidic ionic liquids (BAILs) functionalized hollow organosilica nanospheres ([C3/4Im][OTs/OTf]-Si(Et)Si, C3/4 = Pr/BuSO3H) were synthesized by two steps. The process involved the preparation of hollow nanosphere supports via a toluene-swollen sol-gel co-condensation of 1,2-bis(trimethoxysilyl)ethane and 3-chloropropyltriethoxysilane in the presence of F127, and followed by a successive quaternary ammonization and protonation with imidazole, 1,3-propane/1,4-butane sultone and trifluoromethane sulfonic acid/p-toluenesulfonic acid. The adjustable acid property, hollow inner diameter (5-15 nm) and shell thickness (5-9 nm) of [C3/4Im][OTs/OTf]-Si(Et)Si are achieved by introducing different organic acids and controlling toluene concentration, respectively. The [C3/4Im][OTs/OTf]-Si(Et)Si were applied in selective conversion of fructose to 5-hydroxymethylfurfural (HMF) and 5-ethoxymethylfurfural (EMF) under microwave heating. Under the optimized conditions, the [C4Im][OTs]-Si(Et)Si3.0 nanospheres with the largest inner diameter and the smallest shell thickness exhibit the highest HMF yield (79.4%, 15 min) in fructose dehydration. And the [C3Im][OTf]-Si(Et)Si0.5 nanospheres with the highest acid strength possess the highest EMF yield (70.4%, 30 min) in fructose ethanolysis. The high Brønsted acid-site density and acid strength of [C3/4Im][OTs/OTf]-Si(Et)Si catalysts accompanied by high microwave heating energy lead to excellent dehydration/ethanolysis activity. The product selectivity strongly depended on the BAILs structures and morphological characteristics of the catalyst. More importantly, the [C3/4Im][OTs/OTf]-Si(Et)Si can be reused three times without changes in leaching of BAILs, due to strong covalent bond between BAILs and silicon/carbon framework. This work will provide a simple strategy of chemically bonded BAILs on suitable supports as efficient solid acids, and an approach of combining morphology-controlled solid acids with microwave-heating for catalytic conversion of biomass/derivatives to fuels and value-added chemicals.

Arylborinic acids represent new, efficient, and underexplored hydrogen peroxide-responsive triggers. In contrast to boronic acids, two concomitant oxidative rearrangements are involved in the complete oxidation of these species, which might represent a major limitation for an efficient effector (drug or fluorophore) release. Herein, a comprehensive study of H2 O2 -mediated unsymmetrical arylborinic acid oxidation to investigate the factors that could selectively guide their oxidative rearrangement is described. The o-CF3 substituent was found to be an excellent directing group allowing a complete regioselectivity on borinic acid models. This result was successfully applied to synthesizing new borinic acid-based fluorogenic probes, which exclusively release the fluorescent moiety upon H2 O2 treatment. These compounds maintained their superior kinetic properties compared to boronic acids, thus further enhancing the potential of arylborinic acids as valuable new H2 O2 -sensitive triggers.

In the phosphorous-sulphur two-step process for the clean production of phosphoric acid, a phosphate-rock acid-insoluble residue (PAIR) is a solid filter residue obtained via the phosphoric acid acidolysis of phosphate rock (PR). PAIR combined with other raw materials can be used to prepare cement, ceramics and glasses, opening a potential avenue for large-scale PAIR utilisation. However, the preparation of such materials requires high-temperatures calcination. Understanding the high-temperature thermal properties of PAIR can enable its more targeted comprehensive utilisation or disposal. In this study, the thermal properties and pyrolysis kinetics of PAIR were systematically studied using a multiple heating rate method based on thermogravimetric analysis and a kinetic model. Results showed that from room temperature to 1200 °C, the main changes in the PAIR were the complete removal of fluorine and sulphur, partial removal of phosphorus and conversion of quartz to cristobalite. Moreover, during these processes, H2O(g), NH3, N2, CO2, SO2, P2O5(g), CO, CF3+ and organic gases were volatilised. Herein, the pyrolysis kinetics of PAIR is divided into five stages. Stage 1 (conversion rate ɑ: 0.05-0.2) conforms to the random nucleation and growth as well as the Avrami-Erofeev (n = 2/3) mechanism; the corresponding mechanism function is F(ɑ) = [-Ln(1 - ɑ)]2/3. Stage 2 (ɑ: 0.2-0.4) conforms to the first-order chemical reaction mechanism; the corresponding mechanism function is F(ɑ) = -Ln(1 - ɑ). Stage 3 (ɑ: 0.4-0.6) conforms to the phase boundary-controlled reaction and one-dimensional movement mechanism; the corresponding mechanism function is F(ɑ) = ɑ. Stage 4 (ɑ: 0.6-0.8) conforms to the three-dimensional diffusion process (Jander model); the corresponding mechanism function is F(ɑ) = [1 - (1 - ɑ)1/3]2. Stage 5 (ɑ: 0.6-0.95) conforms to the one-dimensional diffusion process; the corresponding mechanism function is F(ɑ) = ɑ2.