2,5-Di-O-Methylhiascic acid

Herein, we report a strategically novel method for the efficient construction of indole skeletons using 2-phenylisoxazol-5-ones as the starting material. This reaction proceeds via Brønsted acid-promoted α-iminyl cation generation by N-O bond cleavage and a subsequent intramolecular cyclization to afford 1H-indole-3-carboxylic acid, which further undergoes decarboxylation to yield the final product. Control experiments show that N-O bond cleavage and intramolecular cyclization proceed so fast that the 1H-indole-3-carboxylic acid could be isolated in high yields even after 5-10 min. The substrate scope of this transformation is broad, and the desired products are obtained in moderate to good yields. The transition-metal-free reaction condition, CO2 as the sole byproduct, and good practicability add to the synthetic potential of this transformation in the pharmaceutical and flavor industries.

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.