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Catalysis
Published in Aidé Sáenz-Galindo, Adali Oliva Castañeda-Facio, Raúl Rodríguez-Herrera, Green Chemistry and Applications, 2020
Fabiola N. de la Cruz, José Domingo Rivera-Ramírez, Julio López, Miguel A. Vázquez
Since the last decade there has been a growing interest for the development of organic and metallic complexes with photoredox activity, as evidenced by the number of publications in the area, that increased 20 times just in the first half of this lapse. For example, along with the catalysis methods, photoredox and metallic strategies combine perfectly to offer an elegant alternative for the highly efficient decarboxylative cyanation to render chiral nitriles. According to reports, benzylic radicals and Cu(II) species are two key intermediates which emerged jointly during the photocatalytic stage, after Ir(ppy)3, CuBr, TMSCN and a chiral bisoxazoline executed their action in the presence of an appropriate N-hydroxyphthalamide ester (Wang et al., 2017). On the other hand, some interesting examples of compounds with the ability to transform UV-Vis light into chemical energy via a single electron transfer process, include structures of metals in groups 8 and 9 bond to bispyridines, bispyrazines and phenylpyridines, like Ru(bpy)32+, Ru(bpz)32+, Ir(ppy)3, Ir(ppy)2 (dtbbpy)+ and Ir[dF(CF3)ppy]2(dtbbpy)+ (Shaw et al., 2016). Metals such as Pt(II), Au(I), Cu(I), Ni(II) and Fe(II) have shown promising results related with photocatalysis for oxidative addition, reductive elimination, and transmetalation processes (Levin et al., 2016b). Ir is considered a privileged metal in photocatalysis as evidenced by the numerous examples of applications in this area. Intense efforts have been done to improve the efficiency of molecules capable of oxidizing water under natural irradiation and fortunately, the system formed by [Cp*Ir{P(O)(OH)2}3]Na anchored to BiVO4 over a conducting surface and subsequently oxidized with IO–4, has overcome all expectations (Wang et al., 2018c).
Cyclopolymerization of Dienes with Selected Vinyl Monomers
Published in George B. Butler, Cyclopolymerization and Cyclocopolymerization, 2020
New phase transfer catalysts containing oxyethylene oligomers have been synthesized by cyclopolymerization of the divinyl ether of tetraethylene glycol (8-19) a 1,16-diene.2-466 The polymer has a phase transfer activity equal to that of 18-crown-6 as a catalyst for the cyanation of 1-bromohexane by sodium cyanide.
Interfacial Catalysis at Oil/Water Interfaces
Published in Alexander G. Vdlkdv, Interfacial Catalysis, 2002
PT-catalyzed cyanation proceeds efficiently only with alkyl chlorides; alkyl bromides are less efficient whereas iodides are not suitable because Br-produced and particularly I-ions are more lipophilic than CN-and they exert a strong inhibition effect. In such reactions, as for instance cyanation of alkyl halides, there is an important practical problem connected with the necessity to use an excess of NaCN to assure complete conversion of the starting halide into nitrile. Thus, when the reaction is carried out in the traditional way in a solvent system dissolving both reactants, after the reaction is complete, excess of NaCN should be regenerated or detoxified and disposed. The advantage of the PT-catalyzed process carried out in a system comprising two immiscible phases, is that upon separation of the organic phase containing practically pure product, excess of NaCN remaining in the aqueous phase can be readily used for cyanation of the next portion of alkyl halide. By this simple way a counter-current process can be mimicked [16]. Thus, application of PTC for the cyanation reaction assures high yields and purity of the product, elimination of organic solvents, a very simple procedure, and what is particularly important, elimination of the majority of industrial wastes. These advantages of PTC are observed in most other cases of substitution reactions for which this technique can be used.
New room temperature nematogens by cyano tail termination of alkoxy and alkylcyanobiphenyls and their anchoring behavior on metal salt-decorated surface
Published in Liquid Crystals, 2020
Kunlun Wang, Tibor Szilvási, Jake Gold, Huaizhe Yu, Nanqi Bao, Prabin Rai, Manos Mavrikakis, Nicholas L. Abbott, Robert J. Twieg
Different methods were chosen for synthesis of members of the same series based on the availability of relevant starting materials. Most of the cyano tail-terminated alkoxy cyanobiphenyl (CNnOCB) and cyanoterphenyl compounds (CNnOCT) were synthesised by standard alkylation of 4ʹ-hydroxy-4-cyanobiphenyl or 4ʹ'-hydroxy-4-cyanoterphenyl with commercial α,ω-bromoalkanenitriles (n = 3–6 for CB series and n = 3–6 for CT series, Scheme 1). The one exception is CN2OCB, which was synthesised from acrylonitrile and 4ʹ-hydroxy-4-cyanobiphenyl. The reactions proceed smoothly at room temperature and when complete, the product can be precipitated by the addition of water and collected by vacuum filtration. For the seven-carbon chain derivative a method used to synthesise fluorine terminated liquid crystals was utilised since the required bromoalkanenitrile with n = 7 is not available [14]. The hydroxyheptyloxy cyanobiphenyl with a hydroxy group on the tail terminus was first prepared by a standard Mitsunobu reaction between the commercial precursors 4ʹ-hydroxy-4-cyanobiphenyl and excess 1,7-heptanediol (Scheme 1). Next, the terminal alcohol was tosylated with p-TsCl in the presence of triethylamine in good yield. The cyanation was then accomplished using sodium cyanide in DMSO to give the desired cyano tail terminated heptyloxycyanobiphenyl. All the cyano terminated biphenyl compounds were recrystallised from methanol and the analogous terphenyl compounds from acetonitrile for characterisation and thermal behaviour study.
Synthesis of Pd supported on 3,4-diaminobenzoic acid functionalized Fe3O4 nanoparticles as a magnetic catalyst for synthesis of 2-methoxy-2-phenylacetonitrile derivative via a strecker-type reaction under ambient and solvent-free conditions
Published in Journal of Coordination Chemistry, 2021
Hanpeng Zhang, Mohaddese Mirshekari
However, acetals are potent electrophiles toward various nucleophiles under acidic conditions owing to the generation of an oxonium ion intermediate. Many Lewis acids, such as trimethylsilyl triflate, CoCl2 [13], BF3-Et2O [13] and SnCl2 [14], could enhance the cyanation of acetals with trimethylsilyl cyanide (TMSCN). In addition, tetracyanoethylene (TCNE) also catalyzed the reaction of acetals with TMSCN. Conventional procedures must be carried out under anhydrous conditions, which are hard to handle on a large scale. Therefore, the evolvement of less expensive, biocompatible, and easily handled precursors for the synthesis of C–C bonds under neutral, mild and convenient condition is beneficial [15].
Oxidative cyanide-free cyanation on arylboronic acid derivatives using aryl/heteroaryl thiocyanate using novel IL-PdCl4 catalyst under mild condition
Published in Journal of Sulfur Chemistry, 2018
Beena K. Vaghasiya, Shailesh P. Satasia, Rahul P. Thummar, Ronak D. Kamani, Jemin R. Avalani, Nirav H. Sapariya, Dipak K. Raval
Aryl nitriles are important from the view point of a number of drugs [1–3]. They have emerged as basic constituents of dyes and herbicides [4]. They can be transformed into various compounds such as carboxylic acids, amides, amines, imines, aldehydes and tetrazoles because of tunable reactivity of the cyano group [5]. Conventional cyanation methods for the synthesis of nitrile compounds typically employ corresponding organic halides or diazonium salts with copper cyanide [6,7] or the combination of cyanide anion equivalents and transition-metal catalysts [8–12]. Among various available methods, the Sandmeyer and Rosenmund-von Braun reactions have been widely used in aromatic cyanation [13,14]. Many direct cyanation reactions have been reported by metal cyanide (MCN), such as KCN, NaCN, CuCN, Zn(CN)2, AgCN and TMSCN. [15,16]. High toxicity is a serious issue common with all of them. The transition metal-mediated cyanation reactions have been more attractive during these years. Palladium and copper metals are most commonly involved in these reactions [17–20]. The reaction usually proceeds at high temperature with prolonged times. Due to the drawbacks of cyanation using such toxic cyanide sources, many groups have focused on developing cyanide free cyanation by using non-toxic cyanide source like dimethylformamide (DMF) [21]. More recently, cyanation of aryl halides has been developed as a useful alternative for the preparation of aryl nitriles [22,23]. Arylboronic acid derivatives are readily available and easy to handle coupling partners in transition metal catalyzed coupling reactions [24–27]. Much attention has been paid to the direct catalytic oxidative cyanation of arylboronic acid derivatives as a method to access aromatic nitriles.