β‐Functionalization of Carboxylic Anhydrides with β‐Alkyl Substituents through Carbene Organocatalysis

The first NHC‐catalyzed functionalization of carboxylic anhydrides is described. In this reaction, the β carbon behaves as a nucleophilic carbon and undergoes asymmetric reactions with electrophiles. Anhydrides with challenging β‐alkyl substituents work effectively.     

Palladium‐Catalyzed Direct CH Functionalization of Benzoquinone

A direct Pd‐catalyzed C? H functionalization of benzoquinone (BQ) can be controlled to give either mono‐ or disubstituted BQ, including the installation of two different groups in a one‐pot procedure. BQ can now be directly functionalized with aryl, heteroaryl, cycloalkyl, and cycloalkene groups and, moreover, the reaction is conducted in environmentally benign water or acetone as solvents.     

Co3O4纳米晶催化氧化甲烷的理论研究：C-H键活化的晶面效应及活性中心

甲烷是一种在自然界中大量存在的原材料,在取代原油和合成重要化工产品等许多领域具有潜在的应用价值. 然而,由于CH₄中C-H键的键能特别大（约~4.5 eV）,如何实现甲烷的绿色有效转化在化学化工领域仍然是一个挑战. 本文采用密度泛函理论对Co₃O₄（001）和（011）晶面活化甲烷C-H键的机理进行了理论研究,得到了如下结论：（1） CH₄的C-H键在Co₃O₄晶面的解离具有很高的活性,只需要克服大约1 eV的能垒;（2）与Co^2＋相连的Co-O离子对是CH₄活化的活性位点,其中两个带正负电荷的离子对C-H解离起着协同作用,帮助产生Co-CH₃和O-H物种;（3）（011）面的反应活性明显大于（001）面,与实验的观察一致. 本文的计算结果表明,Co₃O₄纳米晶面对CH₄中C-H键的活化表现出明显的晶面效应和结构敏感效应,Co-O离子对活性中心对于活化惰性的C-H键发挥了关键作用.     

锰催化的C?C键生成反应研究进展

迄今为止,贵金属(铑、钯、钌等)在过渡金属催化的碳碳键生成反应中发挥着主导作用,然而使用廉价金属催化剂更符合可持续发展的要求。锰是地壳中含量排第三位的过渡金属,价格便宜,环境危害性小,有潜力成为贵金属催化剂的替代品并发挥其自身独特的反应性。尽管锰参与的当量反应有大量文献报道,目前锰催化的反应尤其是碳碳键生成反应的发展还不成熟,如何实现高效的催化循环是锰催化领域面临的主要难题之一。本文对锰催化的付-克烷基化反应、格氏试剂的酰化反应、偶联反应、碳金属化反应、自由基反应和碳氢键活化反应进行了综述。     

Predicting Regioselectivity in Radical C−H Functionalization of Heterocycles through Machine Learning

Radical C−H bond functionalization provides a versatile approach for elaborating heterocyclic compounds. The synthetic design of this transformation relies heavily on the knowledge of regioselectivity, while a quantified and efficient regioselectivity prediction approach is still elusive. Herein, we report the feasibility of using a machine learning model to predict the transition state barrier from the computed properties of isolated reactants. This enables rapid and reliable regioselectivity prediction for radical C−H bond functionalization of heterocycles. The Random Forest model with physical organic features achieved 94.2 % site accuracy and 89.9 % selectivity accuracy in the out-of-sample test set. The prediction performance was further validated by comparing the machine learning results with additional substituents, heteroarene scaffolds and experimental observations. This work revealed that the combination of mechanism-based computational statistics and machine learning model can serve as a useful strategy for selectivity prediction of organic transformations.     

Transition-metal-free mono- or dinitration of protected anilines

Abstract

An amide-assisted arene nitration is presented, and both mono- and dinitration of protected anilines could be effected by using NaNO₂ and NaNO₃ as the mono- and bisnitrating agents, respectively. This divergent synthesis is transition-metal- and acid-free, and features a broad substrate scope, low cost, and ortho–para selectivity.     

烯丙基化碳纳米管改善丙烯酸酯压敏胶的性能

本文利用γ-甲基丙烯酰氧基丙基三甲氧基硅烷(KH570)对多壁碳纳米管(MWNTs)进行修饰使其表面接枝上烯丙基官能团,与丙烯酸酯类单体进行原位聚合,制备了一种耐高温丙烯酸酯压敏胶(PSA)。 通过傅里叶变换红外光谱仪(FT-IR)、热重分析仪(TGA)和扫描电子显微镜(SEM)表征了MWNTs和丙烯酸酯PSA的结构与性能,探讨了改性MWNTs的质量分数对PSA耐热性能和粘接性能的影响。 结果表明,与未改性的丙烯酸酯PSA相比,当改性MWNTs的质量分数为1.5%时,改性丙烯酸酯PSA的耐热性能和粘接性能最佳,热分解温度从360 ℃提高到了382 ℃,耐热温度从80 ℃提高到了155 ℃,初粘力、持粘力和180°剥离强度分别从2 h和13.66 N/(25 mm)(12号小球)提高到了27 h和17.34 N/(25 mm)(17号小球)。     

An overview of synthetic modification of nitrile group in polymers and applications

The physicochemical properties of polymers are mainly dependent on the nature of polymer backbone and/or pendant groups linked to the main chain. Therefore, synthetic modification of these functional groups via post functionalization is an important approach for obtaining novel polymeric systems with improved properties and targeted applications. In this context, the synthetic modifications of nitrile group in polymers into various useful functionalities have received considerable attention and several interesting applications of the resulting polymers have been identified. The majority of the studies are based on Polyacrylonitrile (PAN), and some isolated examples of nitrile functionalization in copolymers such as Poly (Styrene-co-Acrylonitrile) (SAN), Poly (Acrylonitrile-co-Butadiene-co-Styrene (ABS) and Nitrile Rubber (NBR) are available. These synthetic modifications are mainly accomplished by the reactions such as Nucleophilic addition, cycloaddition, reduction, and hydrolysis using various reagents. These studies describing the post-polymerization modifications of nitrile group in polymers reported during the last three decades are covered in this review.     

Synthesis of the 8,19-Epoxysteroid Eurysterol A

We report the first chemical synthesis of eurysterol A, a cytotoxic and antifungal marine steroidal sulfate with a unique C8−C19 oxy-bridged cholestane skeleton. After C19 hydroxylation of cholesteryl acetate, used as an inexpensive commercial starting material, the challenging oxidative functionalization of ring B was achieved by two different routes to set up a 5α-hydroxy-7-en-6-one moiety. As a key step, an intramolecular oxa-Michael addition was exploited to close the oxy-bridge (8β,19-epoxy unit). DFT calculations show this reversible transformation being exergonic by about −30 kJ mol⁻¹. Along the optimized (scalable) synthetic sequence, the target natural product was obtained in only 11 steps in 5 % overall yield. In addition, an access to (isomeric) 7β,19-epoxy steroids with a previously unknown pentacyclic ring system was discovered.     

Optically Triggered Control of the Charge Carrier Density in Chemically Functionalized Graphene Field Effect Transistors

Field effect transistors (FETs) based on 2D materials are of great interest for applications in ultrathin electronic and sensing devices. Here we demonstrate the possibility to add optical switchability to graphene FETs (GFET) by functionalizing the graphene channel with optically switchable azobenzene molecules. The azobenzene molecules were incorporated to the GFET channel by building a van der Waals heterostructure with a carbon nanomembrane (CNM), which is used as a molecular interposer to attach the azobenzene molecules. Under exposure with 365 nm and 455 nm light, azobenzene molecules transition between cis and trans molecular conformations, respectively, resulting in a switching of the molecular dipole moment. Thus, the effective electric field acting on the GFET channel is tuned by optical stimulation and the carrier density is modulated.