954-67-6Relevant articles and documents
Noncross-linked polystyrene nanoencapsulation of ferric chloride: A novel and reusable heterogeneous macromolecular Lewis acid catalyst toward selective acetylation of alcohols, phenols, amines, and thiols
Alinejad, Sara,Donyapeyma, Ghazaleh,Rahmatpour, Ali
, (2022/01/24)
Ferric chloride has been successfully nanoencapsulated for the first time on a non-cross-linked polystyrene matrix as the shell material via the coacervation technique. The resulting polystyrene nanoencapsulated ferric chloride was used as a novel and rec
Copper-Catalyzed Oxidation of Hydrazones to Diazo Compounds Using Oxygen as the Terminal Oxidant
Liu, Wenbin,Twilton, Jack,Wei, Bo,Lee, Maizie,Hopkins, Melissa N.,Bacsa, John,Stahl, Shannon S.,Davies, Huw M. L.
, p. 2676 - 2683 (2021/03/03)
A mild method for accessing diazo compounds via aerobic oxidation of hydrazones is described. This catalytic transformation employs a Cu(OAc)2/pyridine catalyst and molecular oxygen from ambient air as the terminal oxidant, generating water as the sole byproduct and affording the desired diazo compounds within minutes at room temperature. A broad array of electronically diverse aryldiazo esters, ketones, and amides can be accessed. Pyridine dramatically enhances the rate of the reaction by solubilizing the copper catalyst and serving as the Br?nsted base in the turnover-limiting proton-coupled oxidation of hydrazone by copper(II). Insights gained from mechanistic studies led to expansion of the scope of this method to include diaryl hydrazones, delivering diaryl diazomethane derivatives, which cannot be accessed via established diazo transfer methods. The products of this method may be employed in rhodium carbene catalysis without isolation of the diazo intermediate to afford cyclopropane products in good yield with high enantioselectivity.
Synthesis of Triarylmethanes via Palladium-Catalyzed Suzuki-Miyaura Reactions of Diarylmethyl Esters
Dardir, Amira H.,Casademont-Reig, Irene,Balcells, David,Ellefsen, Jonathan D.,Espinosa, Matthew R.,Hazari, Nilay,Smith, Nicholas E.
supporting information, p. 2332 - 2344 (2021/06/28)
The synthesis of triarylmethanes via Pd-catalyzed Suzuki-Miyaura reactions between diarylmethyl 2,3,4,5,6-pentafluorobenzoates and aryl boronic acids is described. The system operates under mild conditions and has a broad substrate scope, including the coupling of diphenylmethanol derivatives that do not contain extended aromatic substituents. This is significant as these substrates, which result in the types of triarylmethane products that are prevalent in pharmaceuticals, have not previously been compatible with systems for diarylmethyl ester coupling. Furthermore, the reaction can be performed stereospecifically to generate stereoinverted products. On the basis of DFT calculations, it is proposed that the oxidative addition of the diarylmethyl 2,3,4,5,6-pentafluorobenzoate substrate occurs via an SN2 pathway, which results in the inverted products. Mechanistic studies indicate that oxidative addition of the diarylmethyl 2,3,4,5,6-pentafluorobenzoate substrates to (IPr)Pd(0) results in the selective cleavage of the O-C(benzyl) bond in part because of a stabilizing η3-interaction between the benzyl ligand and Pd. This is in contrast to previously described Pd-catalyzed Suzuki-Miyaura reactions involving phenyl esters, which involve selective cleavage of the C(acyl)-O bond, because there is no stabilizing η3-interaction. It is anticipated that this fundamental knowledge will aid the development of new catalytic systems, which use esters as electrophiles in cross-coupling reactions.
Trimethylsilyl Esters as Novel Dual-Purpose Protecting Reagents
Chen, Jyun-Siao,Huang, Po-Hsun,Hsieh, Ya-Chi,Liu, Jen-Wei,Hsu, Hsiao-Lin,Zhang, Kai-Min,Wu, Ren-Tsung,Chang, Ting-Shuo,Liu, Yu-Hao,Wu, Hsin-Ru,Luo, Shun-Yuan
supporting information, p. 754 - 762 (2021/12/02)
Trimethylsilyl esters, AcOTMS, BzOTMS, TCAOTMS, etc., are inexpensive and chemically stable reagents that pose a negligible environmental hazard. Such compounds prove to serve as efficient dualpurpose reagents to respectively achieve acylation and trimethylsilylation of alcohols under acidic or basic conditions. Herein, a detailed study on protection of various substrates and new methodological investigations is described.
Sustainable electrochemical decarboxylative acetoxylation of aminoacids in batch and continuous flow
K?ckinger, Manuel,Hanselmann, Paul,Roberge, Dominique M.,Geotti-Bianchini, Piero,Kappe, C. Oliver,Cantillo, David
supporting information, p. 2382 - 2390 (2021/04/12)
Introduction of acetoxy groups to organic molecules is important for the preparation of many active ingredients and synthetic intermediates. A commonly used and attractive strategy is the oxidative decarboxylation of aliphatic carboxylic acids, which entails the generation of a new C(sp3)-O bond. This reaction has been traditionally carried out using excess amounts of harmful lead(iv) acetate. A sustainable alternative to stoichiometric oxidants is the Hofer-Moest reaction, which relies on the 2-electron anodic oxidation of the carboxylic acid. However, examples showing electrochemical acetoxylation of amino acids are scarce. Herein we present a general and scalable procedure for the anodic decarboxylative acetoxylation of amino acids in batch and continuous flow mode. The procedure has been applied to the derivatization of several natural and synthetic amino acids, including key intermediates for the synthesis of active pharmaceutical ingredients. Good to excellent yields were obtained in all cases. Transfer of the process from batch to a continuous flow cell signficantly increased the reaction throughput and space-time yield, with excellent product yields obtained even in a single-pass. The sustainability of the electrochemical protocol has been examined by evaluating its green metrics. Comparison with the conventional method demonstrates that an electrochemical approach has a significant positive effect on the greenness of the process.
Tropolonate salts as acyl-transfer catalysts under thermal and photochemical conditions: Reaction scope and mechanistic insights
Mai, Binh Khanh,Koenigs, Rene M.,Nguyen, Thanh Vinh,Lyons, Demelza J.M.,Empel, Claire,Pace, Domenic P.,Dinh, An H.
, p. 12596 - 12606 (2020/11/18)
Acyl-transfer catalysis is a frequently used tool to promote the formation of carboxylic acid derivatives, which are important synthetic precursors and target compounds in organic synthesis. However, there have been only a few structural motifs known to efficiently catalyze the acyl-transfer reaction. Herein, we introduce a different acyl-transfer catalytic paradigm based on the tropolone framework. We show that tropolonate salts, due to their strong nucleophilicity and photochemical activity, can promote the coupling reaction between alcohols and carboxylic acid anhydrides or chlorides to give products under thermal or blue light photochemical conditions. Kinetic studies and density functional theory calculations suggest interesting mechanistic insights for reactions promoted by this acyl-transfer catalytic system.
Synthesis of task-specific imidazolium ionic liquid as an efficient catalyst in acetylation of alcohols, phenols, and amines
Chaubey, Snehkrishn A.,Mishra, Roli
, p. 3259 - 3268 (2020/04/17)
Herein, we report the synthesis of task-specific amino-functionalized imidazolium ionic liquid, acetate1-(2-tert-butoxycarbonylamino-ethyl)-3-methyl-3H-imidazol-1-ium; (Boc-NH-EMIM.OAc), as an efficient catalyst for the acetylation of alcohols, phenols, and amines in the presence of acetic anhydride (acetylating reagent). Remarkably, acetic anhydride in the presence of 10?molpercent of catalyst (Boc-NH-EMIM.OAc) under solvent-free conditions showed excellent acetylation activity in shorter duration of time. On the basis of this, a general procedure for acetylation of alcohols, phenols, and amines has been developed. The ionic liquid (Boc-NH-EMIM.OAc) can be readily recovered and reused successfully up to four consecutive cycles without any significant loss of its catalytic activity. We have been able to show that this acetylating method has many advantages. It gives high yields, takes shorter time, and develops the possibility of benign environmental-friendly process.
An efficient metal-free oxidative esterification and amination of benzyl C-H bond
Liu, Saiwen,Chen, Ru,He, Guowen,Zhang, Jin
, (2020/04/09)
An esterification and amination of benzylic C-H bonds was developed by using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) under metal- and iodide-free conditions. Both carboxylic acids and amines could be used as ideal coupling partners for the oxidati
Decarboxylative Acetoxylation of Aliphatic Carboxylic Acids
Senaweera, Sameera,Cartwright, Kaitie C.,Tunge, Jon A.
, p. 12553 - 12561 (2019/10/14)
Organic molecules bearing acetoxy moieties are important functionalities in natural products, drugs, and agricultural chemicals. Synthesis of such molecules via transition metal-catalyzed C-O bond formation can be achieved in the presence of a carefully chosen directing group to alleviate the challenges associated with regioselectivity. An alternative approach is to use ubiquitous carboxylic acids as starting materials and perform a decarboxylative coupling. Herein, we report conditions for a photocatalytic decarboxylative C-O bond formation reaction that provides rapid and facile access to the corresponding acetoxylated products. Mechanistic investigations suggest that the reaction operates via oxidation of the carboxylate followed by rapid decarboxylation and oxidation by Cu(OAc)2
Esterification of Tertiary Amides by Alcohols Through C?N Bond Cleavage over CeO2
Toyao, Takashi,Nurnobi Rashed, Md.,Morita, Yoshitsugu,Kamachi, Takashi,Hakim Siddiki,Ali, Md. A.,Touchy,Kon, Kenichi,Maeno, Zen,Yoshizawa, Kazunari,Shimizu, Ken-ichi
, p. 449 - 456 (2018/09/11)
CeO2 has been found to promote ester forming alcoholysis reactions of tertiary amides. The present catalytic system is operationally simple, recyclable, and it does not require additives. The esterification process displays a wide substrate scope (>45 examples; up to 93 % isolated yield). Results of a density functional theory (DFT) study combined with in situ FT-IR observations indicate that the process proceeds through rate limiting addition of a CeO2 lattice oxygen to the carbonyl group of the adsorbed acetamide species with energy barrier of 17.0 kcal/mol. This value matches well with experimental value (17.9 kcal/mol) obtained from analysis of the Arrhenius plot. Further studies by in situ FT-IR and temperature programmed desorption using probe molecules demonstrate that both acidic and basic properties are important, and consequently, CeO2 showed the best performance for the C?N bond cleavage reaction.
