38418-15-4Relevant academic research and scientific papers
Hydrogen-bond-assisted transition-metal-free catalytic transformation of amides to esters
Huang, Changyu,Li, Jinpeng,Wang, Jiaquan,Zheng, Qingshu,Li, Zhenhua,Tu, Tao
, p. 66 - 71 (2020/11/18)
The amide C-N cleavage has drawn a broad interest in synthetic chemistry, biological process and pharmaceutical industry. Transition-metal, luxury ligand or excess base were always vital to the transformation. Here, we developed a transition-metal-free hydrogen-bond-assisted esterification of amides with only catalytic amount of base. The proposed crucial role of hydrogen bonding for assisting esterification was supported by control experiments, density functional theory (DFT) calculations and kinetic studies. Besides broad substrate scopes and excellent functional groups tolerance, this base-catalyzed protocol complements the conventional transition-metal-catalyzed esterification of amides and provides a new pathway to catalytic cleavage of amide C-N bonds for organic synthesis and pharmaceutical industry. [Figure not available: see fulltext.]
Copper-mediated simple and direct aerobic oxidative esterification of arylacetonitriles with alcohols/phenols
Dong, Jianyu,Chen, Xiuling,Ji, Fangyan,Liu, Lixin,Su, Lebin,Mo, Min,Tang, Jian-Sheng,Zhou, Yongbo
, (2020/10/20)
A simple and direct aerobic oxidative esterification reaction of arylacetonitriles with alcohols/phenols is achieved in the presence of a copper salt and molecular oxygen, which produces a broad range of aryl carboxylic acid esters in good to high yields. Copper salt plays multiple roles in the transformation, which allows the oxygenation of C-H bond, cleavage of inert C-C bond, and formation of C-O bond in one pot without the assistance of any of the acids, bases, ligands, and so on. The reaction provides a simple, direct, and efficient protocol towards functionalized esters, especially aryl benzoates, from readily available starting materials.
Bu 4 NI-Catalyzed C-C Bond Cleavage and Oxidative Esteri??cation of Allyl Alcohols with Toluene Derivatives
Chen, Yaoyao,Cui, Yongmei,Jia, Xueshun,Li, Chengliang,Li, Jian,Sun, Mingming
, p. 3667 - 3674 (2019/09/30)
A novel oxidative esterification of 1-arylprop-2-en-1-ols with toluene derivatives catalyzed by tetrabutylammonium iodide (TBAI) is reported. The optimization of the reaction conditions illustrates that each of experiment parameters including the catalyst, solvent, and oxidant is significant for present oxidative functionalization. This metal-free protocol has a broad substrate scope including the halogen groups for further functionalization and enriches the reactivity profile of allyl alcohol and toluene derivatives. In addition, this protocol represents a new transformation of allyl alcohol involving C-C bond cleavage and C-O bond forming.
Synthesis, characterization and catalytic performances of benzimidazolin-2-iminato actinide (IV) complexes in the Tishchenko reactions for symmetrical and unsymmetrical esters
Liu, Heng,Khononov, Maxim,Fridman, Natalia,Tamm, Matthias,Eisen, Moris S.
, p. 123 - 137 (2017/10/25)
A new family of benzimdazolin-2-iminato actinide?(IV) complexes [(Bim7-MeDipp/MeN)An(N(SiMe3)2)3] (An = U (3), Th (4)) and [(Bim4-MeDipp/MeN)An(N(SiMe3)2)3] (An = U (5), Th (6)) were synthesized and their solid state structures were established by single-crystal X-ray diffraction analysis. The catalytic performances of complexes 3–6 towards the homo- and cross-coupling of aldehydes (Tishchenko reaction) were studied and the thorium complexes 4 and 6 displayed moderate to high activities for the production of the corresponding symmetric and unsymmetrical esters. Coupling of aldehyde and alcohols, known as the tandem proton-transfer esterification, and the intermolecular coupling reaction between aldehyde and trifluoromethylketones were also investigated by these thorium complexes, indicating a complementary method to obtain unsymmetrical esters selectively. Plausible mechanisms for these reactions are proposed based on stoichiometric studies.
Type 2 Ring-Opening Reactions of Cyclopropanated 7-Oxabenzonorbornadienes with Carboxylic Acid Nucleophiles
Carlson, Emily,Hong, Daniel,Tam, William
, p. 4253 - 4259 (2016/11/26)
Ring-opening reactions of strained heterocyclic compounds provide efficient routes to various organic frameworks. In this work, the ability of carboxylic acid nucleophiles to promote ring-opening of cyclopropanated 7-oxabenzonorbornadienes was investigated. Reactions proceeded smoothly to yield 2-naphthylmethyl esters in moderate yields, and optimal conditions were found with the use of 10 mol% p-toluenesulfonic acid monohydrate in dichloroethane heated to 90 °C. The amount of nucleophile could be decreased from a large excess to 8 equivalents without diminishing the yield. When varying the structure of the acid catalyst or carboxylic acid nucleophile, reaction rates showed a marked dependence on acidity of these species. Ring-opening was well tolerated by functionalized substrates, with substitution on the bridgehead or aromatic portions of the molecule. The present work is the second account of this type of reaction, and provides a new route to 2-naphthylmethyl esters. The transformations observed in this work should be useful in predicting the reactivity of similar fused-ring systems.
Mixed Imidazolin-2-iminato-Cp? Thorium(IV) Complexes: Synthesis and Reactivity Toward Oxygen-Containing Substrates
Karmel, Isabell S. R.,Fridman, Natalia,Tamm, Matthias,Eisen, Moris S.
supporting information, p. 2933 - 2942 (2015/06/30)
The mixed pentamethylcyclopentadienyl thorium(IV) imidazolin-2-iminato complexes Cp?2Th(ImDippN)(Me) (2) and Cp?2Th(ImMesN)(Me) (3) were synthesized in quantitative yields via rapid protonolysis of Cp?2Th(Me)2 (1) with the respective neutral imidazolin-2-iminato ligand ImRNH. Cp?2Th(ImDippN)(Me) (2) and Cp?2Th(ImMesN)(Me) (3) display short Th-N bond lengths and large Th-N-C angles. The reactivity of complex 2 and 3 toward oxygen-containing substrates was studied, and the catalytic activity of 2 was compared to the dimethyl (bispentamethyl-cyclopentadienyl) thorium complex 1. Complex 2 was applied in the catalytic Tishchenko reaction with aromatic, heteroaromatic, and branched aliphatic aldehydes, displaying a higher catalytic activity than Cp?2Th(Me)2 and Cp?2Th(ImMesN)(Me). Furthermore, 2 was applied as a catalyst in the crossed Tishchenko reaction and in the oligomerization of bis(aldehydes), as well as in the ring-opening polymerization of ε-caprolactone. In all reactions, the activity of Cp?2Th(ImDippN)(Me) (2) and Cp?2Th(ImMesN)(Me) (3) was higher than that observed for Cp?2Th(Me)2 (1), which can be attributed to the increased electron density introduced by the coordination of the imidazolin-2-iminato ligand. (Chemical Equation Presented).
Ni-catalyzed carboxylation of C(sp2)- and C(sp3)-O bonds with CO2
Correa, Arkaitz,Leon, Thierry,Martin, Ruben
supporting information, p. 1062 - 1069 (2014/02/14)
In recent years a significant progress has been made for the carboxylation of aryl and benzyl halides with CO2, becoming convenient alternatives to the use of stoichiometric amounts of well-defined metal species. Still, however, most of these processes require the use of pyrophoric and air-sensitive reagents and the current methods are mostly restricted to organic halides. Therefore, the discovery of a mild, operationally simple alternate carboxylation that occurs with a wide substrate scope employing readily available coupling partners will be highly desirable. Herein, we report a new protocol that deals with the development of a synergistic activation of CO2 and a rather challenging activation of inert C(sp2)-O and C(sp3)-O bonds derived from simple and cheap alcohols, a previously unrecognized opportunity in this field. This unprecedented carboxylation event is characterized by its simplicity, mild reaction conditions, remarkable selectivity pattern and an excellent chemoselectivity profile using air-, moisture-insensitive and easy-to-handle nickel precatalysts. Our results render our method a powerful alternative, practicality and novelty aside, to commonly used organic halides as counterparts in carboxylation protocols. Furthermore, this study shows, for the first time, that traceless directing groups allow for the reductive coupling of substrates without extended π-systems, a typical requisite in many C-O bond-cleavage reactions. Taking into consideration the limited knowledge in catalytic carboxylative reductive events, and the prospective impact of providing a new tool for accessing valuable carboxylic acids, we believe this work opens up new vistas and allows new tactics in reductive coupling events.
Dimethylbut-2-ynedioate mediated esterification of acids via sp3 C-N bond cleavage of benzylic tertiary amines
Shen, Hao,Lu, Xing,Jiang, Ke-Zhi,Yang, Ke-Fang,Lu, Yixin,Zheng, Zhan-Jiang,Lai, Guo-Qiao,Xu, Li-Wen
supporting information, p. 8916 - 8923 (2012/10/29)
A straightforward synthetic transformation of tertiary amines to the esterification of equimolar amounts of acids was demonstrated in this manuscript. The present protocol can be regarded as a straightforward synthetic transformation of tertiary amines to the esterification of equimolar amounts of acid. Moreover, the reaction is fundamentally new chemistry for the sp 3 C-N bond cleavage coupled with esterification. The esterification reaction conditions are very mild and functional group-tolerated, such as hydrosilanes, alcohols, phenol, and amino acids. A mechanism is proposed in which the tertiary amine reacts with dimethyl but-2-ynedioate to form zwitterionic salt, and then the zwitterionic intermediate subsequently accept hydrogen to assist the nucleophilic attack of oxygen atom of carboxyl group at the benzyl group of tertiary amine, while a separate reaction pathway leads to esterification.
Nonenzymatic dynamic kinetic resolution of α-(arylthio)- and α-(alkylthio)alkanoic acids
Yang, Xing,Birman, Vladimir B.
supporting information; experimental part, p. 5553 - 5555 (2011/07/09)
Dynamic solution: The title acids undergo dynamic kinetic resolution during an enantioselective esterification catalyzed by (S)-homobenzotetramisole ((S)-HBTM; see scheme). This method extends the scope of the carboxylic acid derivatives that are amenable to the nonenzymatic version of this transformation. Copyright
Kinetic resolution of α-substituted alkanoic acids promoted by homobenzotetramisole
Yang, Xing,Birman, Vladimir B.
supporting information; experimental part, p. 11296 - 11304 (2011/10/19)
A new method for catalytic nonenzymatic kinetic resolution of α-substituted alkanoic acids has been developed, which relies on their activation with DCC followed by enantioselective alcoholysis of the intermediate symm-anhydrides in the presence of the amidine-based catalyst homobenzotetramisole (HBTM). Moderate to excellent selectivity factors (s=5-96) have been obtained in the case of several classes of substrates, namely, α-aryl-, α-aryloxy/alkoxy-, α-halo-, α-azido-, and α-phthalimido-alkanoic acids. Under similar conditions, α-(arylthio/alkylthio)-alkanoic acids undergo dynamic kinetic resolution providing corresponding esters in up to 92 % ee and up to 93 % yield. Copyright
