Non-Directed C−H Arylation of Anisole Derivatives via Pd/S,O-Ligand Catalysis

Non-directed C−H arylation is one of the most efficient methods to synthesize biaryl compounds without the need of the prefuctionalization of starting materials, or the installment and removal of directing groups on the substrate. A direct C−H arylation of simple arenes as limiting reactants remains a challenge. Here we disclose a non-directed C−H arylation of anisole derivatives as limiting reagents with aryl iodides under mild reaction conditions. The arylated products are obtained in synthetically useful yields and the arylation of bioactive molecules is also demonstrated. Key to the success of this methodology is the use of a one-step synthesized S,O-ligand.     

Divergent reactivity of phenol- and anisole-tethered donor-acceptor α-diazoketones

The first study of the divergent reactivity of phenol/anisole-tethered donor-acceptor α-diazoketones is described. Four distinct product classes were shown to be accessible from closely related α-diazoketone precursors, with the reaction outcome dependent on the nature of the oxygen substituent on the phenol/anisole ring and the catalyst used to decompose the diazo group. Anisole and TBS-protected derivatives selectively produce three products types (cyclopropanes, tetralones and 1,2-dicarbonyls) while phenols selectively produce spirocyclic dienones.     

Flame structure of laminar premixed anisole flames investigated by photoionization mass spectrometry and photoelectron spectroscopy

Two laminar, premixed, fuel-rich flames fueled by anisole-oxygen-argon mixtures with the same cold gas velocity and pressure were investigated by molecular-beam mass spectrometry at two synchrotron sources where tunable vacuum-ultraviolet radiation enables isomer-resolved photoionization. Decomposition of the very weak O–CH₃ bond in anisole (C₆H₅OCH₃) by unimolecular decomposition yields the resonantly-stabilized phenoxy radical (C₆H₅O). This key intermediate species opens reaction routes to five-membered ring species, such as cyclopentadiene (C₅H₆) and cyclopentadienyl radicals (C₅H₅). Anisole is often discussed as model compound for lignin to study the phenolic-carbon structure in this natural polymer. Measured temperature profiles and mole fractions of many combustion intermediates give detailed information on the flame structure. A very comprehensive reaction mechanism from the literature which includes a sub-scheme for anisole combustion is used for species modeling. Species with the highest measured mole fractions (on the order of 10^?3–10^?2) are CH₃, CH₄, C₂H₂, C₂H₄, C₂H₆, CH₂O, C₅H₅ (cyclopentadienyl radical), C₅H₆ (cyclopentadiene), C₆H₆ (benzene), C₆H₅OH (phenol), and C₆H₅CHO (benzaldehyde). Some are formed in the first destruction steps of anisole, e.g., phenol and benzaldehyde, and their formation will be discussed and with regard to the modeling results. There are three major routes for the fuel destruction: (1) formation of benzaldehyde (C₆H₅CHO), (2) formation of phenol (C₆H₅OH), and (3) unimolecular decomposition of anisole to phenoxy (C₆H₅O) and CH₃ radicals. In the experiment, the phenoxy radical could be measured directly. The phenoxy radical decomposes via a bicyclic structure into the soot precursor C₅H₅ and CO. Formation of larger oxygenated species was observed in both flames. One of them is guaiacol (2-methoxyphenol), which decomposes into fulvenone. The presented speciation data, which contain more than 60 species mole fraction profiles of each flame, give insights into the combustion kinetics of anisole.     

Kinetics and mechanism of oxidation of anisole and substituted anisoles by acid bromate in acetic acid-water mixture

Oxidation of anisoles by acid bromate has been studied in acetic acid-water system in the presence of sulphuric acid. The reaction is first order each in [anisole] and [Br(V)]. The rate of reaction increased with increase in [H⁺] and percentage of acetic acid. The products of oxidation have been identified as ortho and para hydroxyanisoles. From the effect of [H⁺] and [acetic acid] on rate, H ₂ ⁺ BrO₃ has been established as the reactive species. Anisoles having electron-donating substituents in the benzene ring accelerate the rates and vice versa with a Hammett ρ value of −0.6. A mechanism involving the attack of H ₂ ⁺ BrO₃ on ortho/para position of the anisole in the rate-determining step has been proposed.     

Effects of Current upon Electrochemical Catalytic Reforming of Anisole

The reforming of anisole (as model compound of bio-oil) was performed over the NiCuZn-Al₂O₃ catalyst, using a recently-developed electrochemical catalytic reforming (ECR). The influence of the current on the anisole reforming in the ECR process has been investigated. It was observed that anisole reforming was significantly enhanced by the current approached over the catalyst in the electrochemical catalytic process, which was due to the non-uniform temperature distribution in the catalytic bed and the role of the thermal electrons orig-inating from the electrified wire. The maximum hydrogen yield of 88.7% with a carbon conversion of 98.3% was obtained through the ECR reforming of anisole at 700 oC and 4 A. X-ray diffraction was employed to characterize catalyst features and their alterations in the anisole reforming. The apparent activation energy for the anisole reforming is calculated as 99.54 kJ/mol, which is higher than ethanol, acetic acid, and light fraction of bio-oil. It should owe to different physical and chemical properties and reforming mechanism for different hydrocarbons.     

Acylation of Anisole Catalyzed by Hierarchical Porous Hβ Zeolite Modified with Cr

Modified hierarchical porous Hβ zeolite was obtained by metal modification of Hβ zeolite, which was treated with alkaline solution, and the catalysts before and after modification were characterized by means of X-ray diffraction(XRD), nitrogen adsorption-desorption, scanning electron microscopy(SEM), X-ray fluorescence(XRF), NH₃ temperature-programmed desorption and Fourier-transform infrared spectroscopy(FTIR). The activities of acylation of anisole with acetic anhydride were also investigated. The results show that the Hβ zeolite, which was treated with alkaline solution has microporous and mesoporous structures that could improve the diffusion performance of chemical reaction. The amount of acid was modulated with metal modification. The Hβ zeolite modified by 5%(mass fraction) metal chromium had the best catalytic performance. The conversion of acetic anhydride acylation was 93.01% under the optimal conditions, which was higher than that of other catalysts. The catalyst not only showed good activity, but also exhibited a stable performance in regeneration tests.     

Regioselective Iodination of Chlorinated Aromatic Compounds Using Silver Salts

The iodination of chlorinated aromatic compounds using Ag₂SO₄/I₂, AgSbF₆/I₂, AgBF₄/I₂, and AgPF₆/I₂ offers access to iodoarenes that are valuable intermediates in organic synthesis. Specifically, iodination of phenols, anisoles, and anilines with a 3,5-dichloro substitution pattern preferentially yielded the ortho, para, and para iodinated product, respectively. In the case of chlorobenzene and 3-chlorotoluene, AgSbF₆/I₂, AgBF₄/I₂, and AgPF₆/I₂, but not Ag₂SO₄/I₂, selectively introduced the iodine in para position to the chlorine substituent.     

氧化铝负载催化剂作用下以甲醇为烷基化试剂的苯酚气相转化制备苯甲醚(英文)

苯甲醚作为重要的化学品和医药中间体而广泛应用于香料、调味剂及有机合成.液相法是传统的苯甲醚制备工艺,例如在碱性环境下,通过酚钠与硫酸二甲酯反应,溴苯与甲醇反应,酚钠与氯代甲烷反应均可制得苯甲醚.然而,这些方法具有环境处理负担较重和所用原料毒性较强等不足而备受限制.因此,环境友好的绿色苯甲醚合成工艺的开发成为必然,苯酚的气相烷基化工艺由此提出.其中,以碳酸二甲酯(DMC)为烷基化试剂的苯酚气相转化苯甲醚制备方法最受关注.DMC是常用的绿色高效烷基化试剂,但其价格相对较高,在一定程度上增加了苯甲醚制备工艺的复杂性和产品成本.鉴于DMC可由甲醇经氧化羰基化制得,因此以甲醇为烷基化试剂的苯酚气相烷基化转化制备苯甲醚方法成为另一研究热点.然而,与DMC的烷基化性能相比,以甲醇为烷基化试剂的反应产物分布较为复杂,作为苯酚O-烷基化(在苯酚的羟基氧原子上发生的烷基化)产物的苯甲醚相对较难获得,而苯酚的C-烷基化(在苯酚的芳环上发生的烷基化)产物甲基酚产率更易提高.总体而言,与DMC烷基化方法相比,以甲醇为烷基化试剂的苯酚气相转化制备苯甲醚方法有待改善,相关反应机理也更欠明晰,因此具有重要的研究价值.本文研究了γ-Al_2O_3(AA)负载型催化剂上以甲醇为烷基化试剂的苯酚气相转化制备苯甲醚方法,考察了反应温度、气体空速、苯酚与甲醇配比以及催化剂中K负载量和焙烧温度等对反应性能的影响,并分析了该体系中的反应机理.研究表明,在AA上负载的8种化合物(NaCl,MgCl_2,Fe_2(SO_4)_3,Co(NO_3)_2,ZnCl_2,La(NO_3)_3,Ce(NO_3)_3和KH_2PO_4)的催化剂中,KH_2PO_4/AA的催化性能最佳,相应催化剂中K离子负载量为7.53 wt%,于700 oC焙烧8 h.苯酚与甲醇气相反应过程中,苯甲醚最大收率出现在400–450 oC,且随甲醇与苯酚的摩尔比升高而增加,但随空速的提高而降低.另外,在KH_2PO_4/AA催化剂的高K含量,以及低温、高空速、低甲醇含量的物料配比的条件下,对苯酚的O-烷基化过程有利.产物除主产物苯甲醚以外,还有少量甲基苯酚、甲基苯甲醚以及二甲基苯酚等副产物.在K含量为7.53 wt%的KH_2PO_4/AA催化剂作用下,苯甲醚收率最高时反应条件为400–450 oC,空速小于0.18 h儃1,甲醇与苯酚摩尔配比为5.本文所开发的催化剂制备方法简单,反应条件温和,产物收率较高,因此具有较好的应用前景.X射线衍射结果显示,经高温焙烧及固相反应后,KH_2PO_4/AA催化剂中产生了K_3Al_2(PO_4)_3新物相.推测该反应机理是酸性氧化铝促进甲醇脱羟基负离子以及K离子促进酚羟基脱氢质子,所形成的甲基正离子进一步与苯氧基负离子结合得到苯甲醚的"钾离子-酸"双功能催化作用过程     

苯甲醚在复合催化剂上的催化酰化

复合催化剂首次用于催化苯甲醚与酰化剂乙酰氯的酰化反应.发现不同沸石的单独使用仅给出很低产率的对-甲氧基苯乙酮.但是由HY沸石(硅铝比=40)或USY(超稳Y沸石)和SnO组成的复合催化剂的催化活性比单独使用沸石时高得多.增加由USY沸石和不同量的SnO组成的复合催化剂中的SnO的量,导致对-甲氧基苯乙酮产率的提高.由H型沸石(HY和H-ZSM-5沸石)和SnO组成的复合催化剂在苯甲醚与乙酰氯的酰化反应中的催化活性主要取决于所用沸石的硅铝比.