4860-78-0Relevant academic research and scientific papers
Insight into the Mechanism of the Acylation of Alcohols with Acid Anhydrides Catalyzed by Phosphoric Acid Derivatives
Hayashi, Hiroyuki,Yasukochi, Shotaro,Sakamoto, Tatsuhiro,Hatano, Manabu,Ishihara, Kazuaki
, p. 5197 - 5212 (2021/04/12)
Insight into the mechanism of a safe, simple, and inexpensive phosphoric acid (H3PO4)-catalyzed acylation of alcohols with acid anhydrides is described. The corresponding in situ-generated diacylated mixed anhydrides, unlike traditionally proposed monoacylated mixed anhydrides, are proposed as the active species. In particular, the diacylated mixed anhydrides act as efficient catalytic acyl transfer reagents rather than as Br?nsted acid catalysts simply activating acid anhydrides. Remarkably, highly efficient phosphoric acid (1-3 mol %)-catalyzed acylation of alcohols with acid anhydrides was achieved and a 23 g scale synthesis of an ester was demonstrated. Also, phosphoric acid catalyst was effective for synthetically useful esterification from carboxylic acids, alcohols, and acid anhydride. Moreover, with regard to recent developments in chiral 1,1′-bi-2-naphthol (BINOL)-derived phosphoric acid diester catalysts toward asymmetric kinetic resolution of alcohols by acylation, some phosphate diesters were examined. As a result, a 31P NMR study and a kinetics study strongly supported not only the acid-base cooperative mechanism as previously proposed by other researchers but also the mixed anhydride mechanism as presently proposed by us.
KMnO4-catalyzed chemoselective deprotection of acetate and controllable deacetylation-oxidation in one pot
Gurawa, Aakanksha,Kumar, Manoj,Rao, Dodla S.,Kashyap, Sudhir
, p. 16702 - 16707 (2020/10/27)
A novel and efficient protocol for chemoselective deacetylation under ambient conditions was developed using catalytic KMnO4. The stoichiometric use of KMnO4 highlighted the dual role of a heterogeneous oxidant enabling direct access to aromatic aldehydes in one-pot sequential deacetylation-oxidation. The reaction employed an alternative solvent system and allowed the clean transformation of benzyl acetate to sensitive aldehyde in a single step while preventing over-oxidation to acids. Use of inexpensive and readily accessible KMnO4 as an environmentally benign reagent and the ease of the reaction operation were particularly attractive, and enabled the controlled oxidation and facile cleavage of acetate in a preceding step. This journal is
Metal-free transesterification catalyzed by tetramethylammonium methyl carbonate
Hatano, Manabu,Tabata, Yuji,Yoshida, Yurika,Toh, Kohei,Yamashita, Kenji,Ogura, Yoshihiro,Ishihara, Kazuaki
supporting information, p. 1193 - 1198 (2018/03/27)
Environmentally benign metal-free tetramethylammonium methyl carbonate is effective as a catalyst for the chemoselective, scalable, and reusable transesterification of various esters and alcohols in common organic solvents. In situ-generated highly active species, tetramethylammonium alkoxides, can greatly avoid self-decomposition at ≤110 °C, and are reusable. In particular, chelating substrates, such as amino alcohols, diols, triols, sugar derivatives, alkaloids, α-amino acid esters, etc., which deactivate conventional metal salt catalysts, can be used. A 100 gram scale biodiesel production was also demonstrated.
Ceric ammonium nitrate/acetic anhydride: A tunable system for the O-acetylation and mononitration of diversely protected carbohydrates
Seepersaud, Mohindra,Seecharan, Savita,Lalgee, Lorale J.,Jalsa, Nigel Kevin
supporting information, p. 853 - 871 (2017/04/27)
Esterification of a wide range of partially protected carbohydrate derivatives was achieved using acetic anhydride and a catalytic amount of ceric ammonium nitrate (CAN). Compatibility with the commonly used protecting groups was demonstrated, with the es
Diazepinium perchlorate: a neutral catalyst for mild, solvent-free acetylation of carbohydrates and other substances
Giri, Santosh Kumar,Gour, Rajesh,Kartha, K. P. Ravindranathan
, p. 13653 - 13667 (2017/03/11)
Diazepinium perchlorate, an essentially neutral organic salt possessing excellent stability, has been found to be well suited for the acetylation of free as well as partially protected sugars, phenols, thiophenols, thiols and other alcohols as well as amines. The diazepinium perchlorate-catalyzed acetylation is mild, organic and solvent-free and leaves acid sensitive protecting groups such as TBDMS/TBDPS/Tr ethers and isopropylidene/benzylidene acetals present on a substrate unaffected. Regioselective hydroxyl protection in partially protected carbohydrate derivatives/polyhydroxylic compounds was possible and was proved to be a convenient time-saving alternative to the conventional synthesis of such compounds. Easy preparation of the catalyst, mild reaction conditions and an environmentally benign protocol are some of the notable features of this reaction. The results obtained on the acetylation of phenols and thiophenols could be rationalized through their local nucleophilicity index obtained from DFT calculations.
Efficient and selective N-, S- and O-acetylation in TEAA ionic liquid as green solvent. Applications in synthetic carbohydrate chemistry
Lafuente, Leticia,Díaz, Gisela,Bravo, Rodolfo,Ponzinibbio, Agustín
, p. 195 - 200 (2016/02/26)
Background: The ionic liquid triethylammonium acetate (TEAA) was found to be an efficient solvent in the acetylation of alcohols, amines, oximes and thiols to their corresponding acetyl compounds using only a 10% excess of acetic anhydride under mild conditions. Moreover TEAA is not only an inexpensive and recyclable solvent but also an anomeric selective catalyst in the per-O-acetylation of sugar moieties. Methods: Simple and effective organic synthesis protocols were provided for the selective acetylation of several substrates. The products were fully characterized by 1H and 13C NMR spectroscopy and the anomeric ratios were obtained from the 1H spectra. Results: Structurally diverse alcohols, phenols, thiols, amines, carbohydrates and oximes underwent acylation under mild conditions by this procedure to provide the corresponding acetates in excellent yields. TEAA ionic liquid is unique in its capability to act as both, solvent and high selective catalyst. As expected, the reaction proceeds with high b anomeric selectivity for sugars derivatives. Moreover, the ionic liquid was regenerated, recycled and reused for three times without apparent loss of reactivity and selectivity in all cases. Conclusions: The present procedure provides a powerful and versatile acylation method for alcohols, phenols, thiols, amines, oximes and carbohydrates. This protocol is endowed with several unique merits: selectivity, cost-efficiency, atom-economy and mild reaction conditions tolerable to acid sensitive functionalities. With these features, this method may be considered as a better alternative for the acetylation of a wide range of substrates.
Tetranuclear zinc cluster: A dual purpose catalyst for per-: O -acetylation and de- O -acetylation of carbohydrates
Lin, Ting-Wei,Adak, Avijit K.,Lin, Hong-Jyune,Das, Anindya,Hsiao, Wei-Chen,Kuan, Ting-Chun,Lin, Chun-Cheng
, p. 58749 - 58754 (2016/07/07)
The trifluoroacetic acid adduct of tetranuclear zinc cluster Zn4(OCOCF3)6O catalysis in per-O-acetylation and de-O-acetylation of carbohydrates at 70 °C can be tuned by adjusting the reaction medium. Per-O-acetylation of hexopyranoses with a near stoichiometric amount of acetic anhydride in toluene resulted in the exclusive formation of pyranosyl products as an anomeric mixture, whereas de-O-acetylation of acetates occurred in methanol in high yields. In the latter, methanol acts as both nucleophile and solvent, and the reaction conditions were compatible to acid- and base-sensitive groups and amino acid derivatives.
Acyl transfer reactions of carbohydrates, alcohols, phenols, thiols and thiophenols under green reaction conditions
Giri, Santosh Kumar,Kartha, K. P. Ravindranathan
, p. 11687 - 11696 (2015/02/19)
Acyl transfer reactions of various carbohydrates, alcohols, phenols, thiols and thiophenols were achieved at room temperature in high yields and catalytic efficiency in the presence of methane sulfonic acid, a green organic acid, under solvent-free conditions over short time periods. The method is mild enough to allow acid labile substituents such as isopropylidene acetals and trityl ethers on the reacting substrates to be left completely unaffected. Esterification of free mono- and dicarboxylic acids such as acetic acid, cinnamic acid, sialic acid and tartaric acid with alcohols such as menthol, ethanol, methanol or propylene glycol has also been achieved efficiently at room temperature. A comparative study of the method with the silica-sulfuric acid is also reported.
Organocatalysis of nucleophilic substitution reactions by the combined effects of two promoters fused in a molecule: Oligoethylene glycol substituted imidazolium salts
Jadhav, Vinod H.,Kim, Ju-Young,Chi, Dae Yoon,Lee, Sungyul,Kim, Dong Wook
, p. 533 - 542 (2014/01/06)
Oligoethylene glycol substituted imidazolium salts were synthesized as promoters for a range of SN2 reactions, and their efficiency was examined. These tailor-made organic promoters enhanced the nucleophilicity of alkali metal salts significantly through the combined effects of two promoters (oligoethylene glycols and imidazolium salts) in a single molecule. The effects of the oligoethylene glycol side chain length, ionic liquid anions, nucleophiles, and substrates were investigated systematically. [hexaEGmim][OMs] and [dihexaEGim][OMs] showed the highest efficiency for SN2 reactions using alkali metal salts. The role of the terminal hydroxyl groups of the oligoethylene glycol moiety was assessed by examining the relative S N2 yields of chlorination and bromination. The results showed that the hydrogen bonding strength of the hydroxyl groups with the nucleophile is very important. The mechanism for the excellent promotion of SN2 reactions by oligoEGILs was examined by quantum chemical calculations. The results showed that the oxygen atoms in the oligoethylene glycol portion and the ionic liquid anion act on the counter cation K+ or Na+ as a Lewis base, to enhance the reactivity of the metal salts significantly.
Oligoethylene glycols as highly efficient mutifunctional promoters for nucleophilic-substitution reactions
Jadhav, Vinod H.,Jang, Seung Ho,Jeong, Hwan-Jeong,Lim, Seok Tae,Sohn, Myung-Hee,Kim, Ju-Young,Lee, Sungyul,Lee, Ji Woong,Song, Choong Eui,Kim, Dong Wook
supporting information; experimental part, p. 3918 - 3924 (2012/06/01)
Herein, we report the promising use of n-oligoethylene glycols (oligoEGs) as mutifunctional promoters for nucleophilic-substitution reactions employing alkali metal salts. Among the various oligoEGs tested, pentaethylene glycol (pentaEG) had the most efficient catalytic activity. In particular, when compared with other nucleophiles examined, a fluorine nucleophile generated from CsF was significantly activated by the pentaEG promoter. We also performed various facile nucleophilic-displacement reactions, such as the halogenation, acetoxylation, thioacetoxylation, nitrilation, and azidation of various substrates with potassium halides, acetate, thioacetate, cyanide, and sodium azide, respectively, in the presence of the pentaEG promoter. All of these reactions provided their desired products in excellent yields. Furthermore, the combination of pentaEG and a tert-alcohol medium showed tremendous efficiency in the nucleophilic-displacement reactions (fluorination and methoxylation) of base-sensitive substrates with basic nucleophiles (cesium fluoride and potassium methoxide, respectively). The catalytic role of oligoEGs was examined by quantum-chemical methods. The oxygen atoms in oligoEGs were found to act as Lewis bases on the metal cations to produce the "flexible" nucleophile, whereas the two terminal hydroxy (OH) groups acted as "anchors" to orientate the nucleophile and the substrate into an ideal configuration for the reaction. The EG race: OligoEGs, such as pentaethylene glycol (pentaEG), act as mutifunctional promoters for nucleophilic-substitution reactions with the corresponding alkali-metal salts. The combination of pentaEG and a tert-alcohol media system showed tremendous efficiency in the fluorination and methoxylation of base-sensitive substrates by using the corresponding basic nucleophiles (see figure). Copyright
