Here, an organocatalytic asymmetric [1,3]-sigmatropic rearrangement process for aryl ether insertion through C─O bond cleavage and downstream transformation is reported, enabling the practical and atom-economic synthesis of diverse valuable chiral benzofuran derivatives bearing a quaternary carbon stereocenter. The reaction shows a wide substrate scope, yielding moderate to good products with excellent enantioselectivity and diastereoselectivity (up to >99% ee and >99:1 d.r.). Initial biological activity tests suggest that the resulting enantioenriched benzofuran products hold potential as anticancer agents.

2,6-Di-tert-butyl-4-methylphenol (BHT) is an excellent antioxidant that is easily oxidized to 2,6-di-tert-butyl-4-hydroperoxyl-4-methyl-2,5-cyclohexadienone (BHTOOH). For the safety of BHT production and usage, it is meaningful to study the thermal stability and decomposition properties of BHT and BHTOOH. In this paper, the thermal decomposition properties of BHT and BHTOOH were compared by the mini closed pressure vessel test (MCPVT) and differential scanning calorimetry (DSC). Their kinetics of thermal decomposition were studied using thermogravimetric analysis (TGA). The thermal decomposition products of BHT and BHTOOH were analyzed by gas chromatography-mass spectrometry (GC–MS). The results show that there was no significant change in temperature pressure when BHT was warmed up under a nitrogen atmosphere, indicating that BHT was stable within 400 K. The thermal decomposition reaction of BHTOOH was rapid with an initial reaction temperature of 375.2 K. The initial exothermic temperature (Ti) and heat release (QDSC) of DSC were 384.9 K and 865.0 J g−1, respectively. The apparent activation energies (Ea) for the thermal decomposition reactions of BHT and BHTOOH calculated by the Kissinger method were 151.8 kJ mol−1 and 66.07 kJ mol−1, respectively. The main decomposition products of BHT were isobutene and 2-tert-butyl-4-methylphenol. The thermal decomposition products of BHTOOH included BHT, 2,6-di-tert-butyl-4-ethylphenol, 3,5-di-tert-butyl-4-hydroxybenzaldehyde, 4,4′-(1,2-ethanediyl) bis [2,6-bis (1,1-dimethylethyl) phenol, etc. Based on the thermal decomposition behavior and products, the reaction pathway has been described. These results indicate that BHT is a potential thermal hazard during production, storage and application. For the safety of the chemical industry, the oxidation of BHT should be avoided.

It is a new attempt to investigate thermal stability and reactivity of four 3-Phenyl-2-propene compounds by MCPVT. The temperature of initial oxygen absorption (Ta) and rapid oxidation(TR) were calculated. Results showed that four 3-Phenyl-2-propene compounds were stable under nitrogen atmosphere. The Ta of cinnamaldehyde, cinnamyl alcohol, β-methylstyrene and cinnamic acid were 271.25K, 292.375K, 323.125K, and 363.875K, and the TR of cinnamaldehyde, cinnamyl alcohol, β-methylstyrene and cinnamic acid were 301.125K, 332.75K, 357.91K, and 385.375K, respectively. The oxidation reactivity order was derived: cinnamaldehyde > cinnamyl alcohol > β-Methylstyrene > cinnamic acid. The oxidation kinetics of four 3-Phenyl-2-propene compounds was calculated, which showed a second-order reaction. Peroxide concentrations of initial oxidation were determined by iodimetry, and the oxidation products were analyzed by gas chromatography-mass spectrometry (GC-MS). Results showed peroxides were generated. According to the complex oxidation products, important insights into the pathways of oxidation were provided.

Butylated hydroxytoluene (BHT) is an excellent antioxidant widely used in food, poly-mer materials, and other fields. In order to understand the hazards of BHT, it is necessary to study its thermal stability, oxidation properties, and reaction products. This paper investigated BHT's oxidation characteristics and products using a mini-closed pressure vessel test (MCPVT), UV radi-ation reaction method, iodometric method, and gas chromatography-mass spectrometry (GC-MS). The MCPVT results showed that no chemical reaction of BHT was observed under a nitrogen atmosphere even when the temperature was increased to 450 K, which indicated that it was stable. However, BHT was readily oxidized under an oxygen atmosphere with an initial oxidation temper-ature of 332 K. Notably, oxidation reactions can occur as low as 293 K under 365 nm UV radia-tions in the atmosphere. The kinetics of the initial oxidation of BHT was investigated. The kinetics of the reaction of BHT in MCPVT was a second-order reaction with the kinetic equation lnk =-1. 2194 x 104(1/T) + 21.4. And Ea = 101.4 kJ mol-1. The difference is that a pseudo-first-order reac-tion was shown under UV radiation, with a linear relationship between the apparent activation energy and the logarithm of the light intensity (I): Ea =-1.878 lnI + 74.56, the apparent activation energy was significantly reduced compared to the former, indicating that UV light has a great effect on the oxidation of BHT. The peroxide value of the BHT oxidation product in MCPVT was deter-mined with the iodometric method. When the reaction was carried out at 358 K for 8 h, the peroxide value of BHT was 3.2 mmol kg -1. The main oxidation products of BHT were identified with GC- MS, such as 2, 6-di-tert-butyl-p-benzoquinone, 1-(2, 4, 6-trihydroxyphenyl) butanone, 3, 5-di-tert- butyl- 4-hydroxybenzaldehyde,3, 5-di-tert-butyl-4-hydroxyacetophenone. Based on these oxidation products, the oxidation pathway of BHT was described. In conclusion, the oxidation characteristics of BHT were studied in detail with MCPVT, and a method for evaluating thermal stability was developed. UV radiation made BHT more susceptible to oxidation reactions. These data provided a reference for BHT's storage, transportation, and safety evaluation. (c) 2023 The Author(s). Published by Elsevier B.V. on behalf of King Saud University. This is an open

In this study, the oxidation characteristics of isoprene were investigated using a custom-designed mini closed pressure vessel test (MCPVT). The results show that isoprene is unstable and polymerization occurs under a nitrogen atmosphere. Under an oxygen atmosphere, the oxidation process of isoprene was divided into three stages: (1) isoprene reacts with oxygen to produce peroxide; (2) Peroxides produce free radicals through thermal decomposition; (3) Free radicals cause complex oxidation and thermal runaway reactions. The oxidation of isoprene conforms to the second-order reaction kinetics, and the activation energy was 86.88 kJ·mol −1 . The thermal decomposition characteristics of the total oxidation product and purified peroxide mixture were determined by differential scanning calorimetry (DSC). The initial exothermic temperatures T on were 371.17 K and 365.84 K, respectively. And the decomposition heat Q DSC were 816.66 J·g −1 and 991.08 J·g −1 , respectively. It indicates that high concentration of isoprene peroxide has a high risk of thermal runaway. The results of thermal runaway experiment showed that the temperature and pressure of isoprene oxidation were prone to rise rapidly, which indicates that the oxidation reaction was dangerous. The reaction products of isoprene were analyzed by gas chromatography-mass spectrometry (GC–MS). The main oxidation products were methyl vinyl ketone, methacrolein, 3-methylfuran, etc. The main thermal runaway products were dimethoxymethane, 2,3-pentanedione, naphthalene, etc. Based on the reaction products, the possible reaction pathway of isoprene was proposed.

1,3-Butadiene is the simplest conjugated diene, which is widely used in polymer materials, organic synthesis, and other fields. The investigation of its thermal stability and oxidation characteristics is necessary for production, transportation, and use safety. The pressure and temperature behavior of the autoxidation reaction of 1,3-butadiene with oxygen were determined using a custom-designed mini closed pressure vessel test (MCPVT). The effects of free radical initiators CHP and AIBN on the oxidation reaction were investigated. The thermal decomposition characteristics of oxidation products were measured by differential scanning calorimetry (DSC), and its hazards were discussed. The results showed that the oxidation reaction of 1,3-butadiene was easy to occur. Moreover, the activation energies of autoxidation, CHP-initiated oxidation, and AIBN-initiated oxidation reaction were 20.85 kJ·mol−1, 33.30 kJ·mol−1, and 56.27 kJ·mol−1, respectively. In addition, the oxidation products were analyzed by headspace sampler-gas chromatography-mass spectrometry (HS-GC–MS), GC–MS, and iodometry. Some of 1,3-butadiene oxidation products under three conditions are the same, for example, 3-butene-1,2-diol, 4-vinylcyclohexene, 2(5H)-furanone, 2-propen-1-ol, and 2,6-cyclooctadien-1-ol. According to the reaction products, the oxidation reaction pathway of 1,3-butadiene was described. The research results are significant for avoiding fire and explosion accidents in the production, transportation, and application of 1,3-butadiene.

It has been a challenge to synthesize macrolide musk in excellent yields with high purity. KF-La/γ-Al 2 O 3 catalyst was prepared from a highly basic mesoporous framework using a mild method. The prepared KF-La/γ-Al 2 O 3 catalyst was employed for the synthesis of cyclopentadecanolide from methyl 15-hydroxypentadecanoate. The morphology and structure of prepared catalysts were characterized using XRD, TG-DTG, SEM, EDX, TEM, BET and CO 2 -TPD. The results revealed that the K 3 AlF 6 and LaOF are produced on the surface of KF-La/γ-Al 2 O 3 , and LaO can promote the dispersion of KF on the surface of Al 2 O 3 . Catalysts pore size main distribution ranges between 10 and 30 nm, the maximum CO 2 desorption temperature is 715°C when the La loading is 25%. Because F − ion has a higher electronegativity than O 2− ion, the KF-promoted metal oxide (Al 2 O 3 or/and La 2 O 3 ) contained more strong basic sites, compared with that of the corresponding metal oxide. The yield of cyclopentadecanolide obtained at 0.5 g KF-25La/γ-Al 2 O 3 catalyst and a reaction temperature of 190°C for 7 h were 58.50%, and the content after reactive distillation is 98.8%. The KF-La/γ-Al 2 O 3 catalyst has a larger pore size and basic strength, which is more conducive to the macrolactonization of long-chain hydroxy ester.

The reaction process of gaseous 1,3-butadiene following ultraviolet irradiation at the temperature range from 298 to 323 K under nitrogen atmosphere was monitored by UV–vis spectrophotometry. A gaseous mini-reactor was used as a reaction vessel and could be directly monitored in a UV–vis spectrophotometer. We investigated the reactivity and kinetics of 1,3-butadiene under non-UV and UV irradiation to evaluate its photochemical stability. A second-order kinetic model with 50.48 kJ·mol –1 activation energy fitted the reaction data for non-UV irradiation, whereas a first-order kinetic model was appropriate in the case of UV irradiation with activation energies of 19.92–43.65 kJ mol –1 . This indicates that ultraviolet light could accelerate the photolysis reaction rate of 1,3-butadiene. In addition, the reaction products were determined using gas chromatography-mass spectrometry (GC–MS), and the reaction pathways were identified. The photolysis of 1,3-butadiene gave rise to various volatile products by cleavage and rearrangement of single C–C bonds. The differences between dimerization and dissociation of 1,3-butadiene under ultraviolet irradiation were elucidated by combining experimental and theoretical methods. The present findings provide fundamental insight into the photochemistry of 1,3-butadiene compounds.

A new attempt to investigate the thermal stability and reactivity of four 3-phenyl-2-propene compounds with oxygen by MCPVT has been reported.

The thermal oxidation reaction of 2,5-dimethylfuran (DMF) was investigated using a custom-designed mini closed pressure vessel test (MCPVT) and traced by H-1 nuclear magnetic resonance(H-1 NMR). The oxidation behavior was monitored by-via temperature-time (T-t) and pressure-time (p-t) plots of MCPVT recording. Oxidation products were determined via gas chromatography-mass spectrometry (GC-MS), and the generated peroxide was examined by iodimetry and thin-layer chromatography (TLC), with the thermal decomposition hazard evaluation by differential scanning calorimeter (DSC) and MCPVT. Results show that the DMF oxidation reaction proceeded through initial oxygen absorption at 39.3 degrees C, followed by an exothermic self-accelerating oxidation at 84.5 degrees C. DMF could form high level peroxide in auto-oxidation; the decomposition of peroxides would lead to the radical oxidation that the generated center dot OH radical mainly attacks on the position 2/5 of DMF with subsequent addition of O-2 initiating ring-opening reaction, in which DMF was firstly converted to cis-3-hexene-2,5-dione, and then produced the trans-3-hexene-2,5-dione with strong photoisomerism. DMF oxidation showed a high level of residue formation, and those solid products contained considerable amount of peroxides with a high thermal hazard; its exothermic onset temperature (T0) and decomposition heat (QDSC) of 58.8 degrees C and 1982.3 J.g(-1), and the decomposition maximum temperature rising rate (dT/dt) max and maximum of pressure rising rate (dp/dt) max was 9.98 degrees C.s(-1) and 291 kPa.s(-1), respectively. Thermal decomposition of those peroxide products could give rise to thermal runaway of DMF oxidation, and further transformed into a detonation possibly.

An organocatalytic approach to installing various alcohols into the carbonyl of α,β-unsaturated ketones mediated by VQM intermediates was achieved, followed by dearomatization to provide the stereo-defined cyclic ethers via a cascade process. Along with the transformations, this strategy affords efficient access to the underexplored chiral cyclic ether chemospace.

A self-designed mini gas–solid reaction device was applied as promising equipment to investigate the oxidation characteristics and kinetics of the glycerol ester of rosin (GER) under 254 nm UV irradiation in air.

建立一种同时测定微生物转化肉桂醛体系中10种天然苯基香精香料(苯甲醇、苯甲醛、苯甲酸、苯乙醇、苯乙酮、肉桂醇、肉桂醛、肉桂酸、3-苯丙醇和3-苯丙醛)的高效液相色谱分析方法.试样经无水乙醇提取,离心,过滤后进样.色谱分析采用SunFireTMC18色谱柱(250 mm×4.6 mm,5μm),以甲醇:乙腈:水:冰醋酸=28.4:18:53.6:0.04(体积比)为流动相,流速1.0 mL/min,紫外检测器检测.10种待测物在2.00 mg/L～318.60 mg/L范围内线性关系良好(0.9987≤R2≤0.9996),方法检出限(method detection limit,LOD,S/N=3)为0.36 mg/L～1.16 mg/L,在低、中、高3个加标水平下的平均回收率为92.13％～102.90％,RSD为0.62％～4.01％.该方法可用于微生物转化肉桂醛合成天然苯基香料的生物反应体系的成分分析,也可用于生物转化肉桂醛合成天然香料的菌种选育工作中.

为高效筛选转化肉桂醛为天然肉桂醇的微生物菌株,建立直接、快速测定生物转化液中的肉桂醇、肉桂醛和肉桂酸含量的多阶导数紫外光谱法.对3个组分的紫外吸收光谱进行二阶或三阶导数处理,选择各组分合适的检测波长;在选定波长下建立各组分吸收光谱的导数值对质量浓度的工作曲线.结果 表明:肉桂醛和肉桂酸分别在320 nm和306 nm波长处的二阶导数值与其质量浓度分别在0.52～9.27 mg/L和0.51～9.24 mg/L范围内有良好的线性关系,平均回收率分别为103.3％和104.1％,相对标准偏差(relative standard deviation,RSD)为4.1％和2.1％;肉桂醇在256 nm波长处的三阶导数值与其质量浓度在0.55～5.47 mg/L范围内有良好的线性关系,平均回收率为98.0％,RSD为3.5％.利用该方法,样品中各组分不需提取分离即可直接稀释测定,可用于微生物转化肉桂醛制备肉桂醇反应实验菌株的快速高效筛选.

Pressure and temperature behavior of the cinnamaldehyde oxidation process was determined using a custom-designed mini closed pressure vessel test (MCPVT), which is a new method to investigate the stability and hazard assesment of the cinnamaldehyde oxidation reaction. The oxidation products were analyzed by gas chromatography-mass spectrometry (GC-MS). The results showed that cinnamaldehyde was stable under nitrogen atmosphere but very unstable under oxygen atmosphere. The initial oxidation products were analyzed by iodimetry and the cinnamaldehyde peroxide value could reach 139.44 mmol kg(-1) when the oxidation temperature was 308 K. The oxidation kinetics of cinnamaldehyde were studied by using the pressure versus time (P-t) curves obtained from the MCPVT process. The reaction is a second-order reaction, the kinetic equation is ln k = -2233.66 x (1/T) + 11.19, and the activation energy E-a is 18.57 kJ mol(-1) at 308-338 K. The explosion of the cinnamaldehyde oxidation reaction was observed by MCPVT, in which the onset temperature was 373 K. The main products of cinnamaldehyde oxidation are acetaldehyde, benzaldehyde, phenylacetaldehyde, acetophenone, 2-hydroxyphenyl acetone, cinnamaldehyde epoxide, benzoic acid, and cinnamic acid. Oxidation is a three-step process: (1) cinnamaldehyde reacts with oxygen to form peroxides; (2) complex oxidation reactions are caused by the thermal decomposition of peroxides; (3) rapid oxidation and thermal decomposition lead to explosion hazard.

用小型密闭压力容器实验(MCPVT)分别跟踪测定了1,3-丁二烯在氮气和氧气氛围下温度随时间的变化(T-t)和压力随时间的变化(p-t).利用p-t曲线构建了1,3-丁二烯初期氧化反应动力学.结果表明,在氮气条件下,即使温度达到388.15 K也未检测到1,3-丁二烯发生化学反应.1,3-丁二烯与氧气在343.15～363.15 K范围内发生了氧化反应,反应器内的压力减小.1,3-丁二烯与氧气的初期氧化反应动力学是二级反应.另外,还考察了氧气过量和1,3-丁二烯过量时两种特殊情况下的假一级氧化反应动力学.探讨了过渡态的热力学参数,计算结果表明,1,3-丁二烯的热氧化是一个有序的分子数减少过程.用气相色谱-质谱联用仪和碘量法分析了氧化反应产物,其产物有呋喃和过氧化物.

The thermal oxidation characteristics of abietic acid were investigated through tracing the oxidation process in custom-designed mini closed pressure vessel test under isothermal and step temperature conditions. Peroxide generation and the peroxide value of abietic acid oxidation process were measured using thin-layer chromatographic analysis and iodimetry. The primary oxidation product-peroxide-was separated by column chromatography with further structure characterization, and its thermal decomposition characteristics were assessed via a differential scanning calorimeter (DSC). The oxidation was mainly initiated through the radical generation from hydrogen abstraction on the unsaturated conjugated double bonds of abietic acid above 343 K. The main hydroperoxide, 7-hydroperoxy-13-abiet-8(14)-enoic acid, was found in abietic acid with a high peroxide value. The exothermic onset temperature (T-0) and decomposition heat (Q(DSC)) of this peroxide were 353.94 K and 545.37 J.g(-1), respectively. Finally, a second-stage oxidation process of abietic acid was first investigated when the temperature reached the abietic acid melt point (448 K) with complex oxidation products forming, such as dehydroabietic acid, palustric acid, 7-oxodehydroabietic acid, neoabietic acid, 7-methoxy-tetradehydroabietic acid, 12-deoxyroyleanone acid, and 12-methoxy-abietic acid.

采用溶剂法提取纯化柠檬桉树脂总黄酮,对粗提物(A)和纯化物进行抗氧化活性研究.用盐酸-锌粉、浓硫酸、三氯化铁、硝酸铝等方法定性鉴别树脂总黄酮,以芦丁为标准品定量分析树脂总黄酮含量为4.64％(以柠檬桉树脂固体粉末的质量为基准,下同).粗提物(A)经氯仿-乙酸丁酯、氯仿-二甲基甲酰胺、二甲基甲酰胺-氯仿两次超声萃取后得到纯化物B、C、D中总黄酮质量分数分别为10.39％、18.03％、44.15％.考察了A、B、C、D对2,2-二苯基-1-苦味基肼自由基(DPPH·)的清除活性、总抗氧化能力和还原能力.结果表明,质量浓度为0.14 g/L时,A、B、C、D对DPPH·的清除活性分别为91.75％、74.22％、88.44％、91.56％;总抗氧化能力分别为19.99、1.75、4.39、3.79μmol芦丁当量(RE)/g;还原能力分别为1.16、0.36、0.39、0.45μmol RE/g.

蒜头果内生真菌以神经酸结晶母液为培养基质,通过发酵能够获得富含神经酸的微生物油脂.神经酸结晶母液中含有的脂肪酸主要有硬脂酸、油酸、花生酸、芥酸和神经酸,为了跟踪监测微生物油脂中这5种脂肪酸的变化,建立了用气相色谱法同时定量测定这5种脂肪酸组分的分析方法.采用Rtx-Wax@柱(30 m×0.25 mm,0.25 μm),升温程序为初始温度180℃,保留1 min,以5℃/min升至240℃,保留9 min.结果 表明,硬脂酸甲酯、油酸甲酯、花生酸甲酯、芥酸甲酯和神经酸甲酯分别在0.24～9.57、0.50～9.95、0.20～24.75、0.24～8.00 mg/mL和0.10～11.08 mg/mL范围内呈良好的线性关系(r＞0.999),平均回收率分别为99.90％、98.31％、102.24％、104.38％和98.62％,相对标准偏差分别为0.93％、3.13％、1.51％、3.37％和1.66％.该法适用于测定蒜头果内生真菌发酵产微生物油脂中的脂肪酸.

A self-designed reaction device was used as a promising equipment to investigate the oxidation characteristics and kinetics of rosin pentaerythritol ester (RPE) under UV irradiation. Photo-oxidation kinetics and the initial quantum yield (Φ) of RPE were calculated. The initial oxidation product of the photo-oxidation reaction—peroxide was analyzed by iodimetry. The peroxide concentration is related to the light intensity (I) and the temperature (T), and the increasing T and I would destabilize the RPE by accelerating peroxide forming. Photo-oxidation of RPE follows the pseudo first-order reaction kinetics. The relationship between activation energy and logarithm of light intensity (ln I) is linear, and it is expressed as Ea = −4.937ln I + 45.565. Φ was calculated by the photo-oxidation kinetics, and the average value of Φ was 7.19% in the light intensity range of 200–800 μW cm−2. This research can provide fundamental information for application of RPE, and help obtain a better understanding of the stability of rosin esters.