612-33-9Relevant academic research and scientific papers
Direct Amidation of Esters by Ball Milling**
Barreteau, Fabien,Battilocchio, Claudio,Browne, Duncan L.,Godineau, Edouard,Leitch, Jamie A.,Nicholson, William I.,Payne, Riley,Priestley, Ian
supporting information, p. 21868 - 21874 (2021/09/02)
The direct mechanochemical amidation of esters by ball milling is described. The operationally simple procedure requires an ester, an amine, and substoichiometric KOtBu and was used to prepare a large and diverse library of 78 amide structures with modest to excellent efficiency. Heteroaromatic and heterocyclic components are specifically shown to be amenable to this mechanochemical protocol. This direct synthesis platform has been applied to the synthesis of active pharmaceutical ingredients (APIs) and agrochemicals as well as the gram-scale synthesis of an active pharmaceutical, all in the absence of a reaction solvent.
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.]
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.
Chemoselective Tertiary C?H Hydroxylation for Late-Stage Functionalization with Mn(PDP)/Chloroacetic Acid Catalysis
Chambers, Rachel K.,Zhao, Jinpeng,Delaney, Connor P.,White, M. Christina
supporting information, p. 417 - 423 (2019/12/27)
Aromatic and heterocyclic functionality are ubiquitous in pharmaceuticals. Herein, we disclose a new Mn(PDP) catalyst system using chloroacetic acid additive capable of chemoselectively oxidizing remote tertiary C(sp3)?H bonds in the presence of a broad range of aromatic and heterocyclic moieties. Although catalyst loadings can be lowered to 0.1 mol% under a Mn(PDP)/acetic acid system for aromatic and non-basic nitrogen heterocycle substrates, the Mn(PDP)/chloroacetic acid system generally affords 10–15% higher isolated yields on these substrates and is uniquely effective for remote C(sp3)?H hydroxylations in substrates housing basic nitrogen heterocycles. The demonstrated ability to perform Mn(PDP)/chloroacetic acid C(sp3)?H oxidations in pharmaceutically relevant complex molecules on multi-gram scales will facilitate drug discovery processes via late-stage functionalization. (Figure presented.).
Base-catalyzed selective esterification of alcohols with unactivated esters
Zhang, Chunyan,Zhang, Guoying,Luo, Shizhong,Wang, Chunfu,Li, Huiping
supporting information, p. 8467 - 8471 (2018/12/01)
A practical and efficient base-catalyzed esterification has been developed for the facile synthesis of a broad range of esters from simple alcohols with unactivated tert-butyl esters. This protocol could be conducted at mild conditions, providing esters in high to excellent yields with good functional tolerance. Mechanistic studies provided evidence of an exchange of the tert-butyl alkoxide metal with the alcohol, producing a new alkoxide to participate in the transesterification reaction.
Fluoride-Catalyzed Esterification of Amides
Wu, Hongxiang,Guo, Weijie,Daniel, Stelck,Li, Yue,Liu, Chao,Zeng, Zhuo
, p. 3444 - 3447 (2018/02/21)
In recent years, it has been demonstrated that amide carbon–nitrogen bonds can be activated and selectively cleaved using transition metal catalysts. However, these methodologies have been restricted to specific amides; a one-to-one relationship exists between the catalytic system and the amides and also uses large amounts of transition-metal catalysts and ligands. Hence, we now report a general strategy for esterification of common amides using fluoride as a catalyst. This method shows high functional group tolerance, and notably it requires only a slight excess of the alcohol nucleophile, which is a rare case in transition-metal-free amide transformations. Moreover, this approach may provide a new understanding for further studies on esterification of amides and is expected to stimulate the development of alternative methods for direct functionalization of amides.
Visible-Light Photocatalysis Employing Dye-Sensitized Semiconductor: Selective Aerobic Oxidation of Benzyl Ethers
Ren, Li,Yang, Ming-Meng,Tung, Chen-Ho,Wu, Li-Zhu,Cong, Huan
, p. 8134 - 8138 (2017/12/08)
The aerobic oxidation is an attractive approach toward environmentally benign synthesis of fine chemicals. In addition, dye-sensitized semiconductors are underdeveloped photocatalysts for selective organic synthesis. With the aid of catalytic eosin Y-sensitized titanium dioxide, we have developed efficient aerobic photooxidation of benzyl ethers to benzoates, featuring low cost, high atom economy, broad substrate scope, and user-friendly setup. Furthermore, preliminary mechanistic studies established that the reaction pathway likely entails a photoinduced, radical-based two-step process via an isolable peroxide intermediate.
Kinetic Modeling of the Nickel-Catalyzed Esterification of Amides
Weires, Nicholas A.,Caspi, Daniel D.,Garg, Neil K.
, p. 4381 - 4385 (2017/07/24)
Nickel-catalyzed coupling reactions provide exciting tools in chemical synthesis. However, most methodologies in this area require high catalyst loadings, which commonly range from 10-20 mol % nickel. Through an academic-industrial collaboration, we demonstrate that kinetic modeling can be used strategically to overcome this problem, specifically within the context of the Ni-catalyzed conversion of amides to esters. The successful application of this methodology to a multigram-scale coupling, using only 0.4 mol % Ni, highlights the impact of this endeavor.
Sulfination of Alcohols with p-Toluenesulfonylmethyl Isocyanide under Metal-Free Conditions: A Mitsunobu Approach
Kadari, Lingaswamy,Radha Krishna, Palakodety,Lakshmi Prapurna
supporting information, p. 3863 - 3868 (2016/12/16)
A Mitsunobu approach for the synthesis of sulfinate esters by direct nucleophilic substitution of alcohols is described. The salient features of this strategy include neutral and metal-free conditions for the rapid synthesis of sulfinates in high yields. The present protocol using p-toluenesulfonylmethyl isocyanide (TosMIC) and the triphenylphosphine (TPP)/diisopropyl azodicarboxylate (DIAD) reagent system represents the general synthetic route to this important class of compounds. (Figure presented.).
Benchtop Delivery of Ni(cod)2 using Paraffin Capsules
Dander, Jacob E.,Weires, Nicholas A.,Garg, Neil K.
supporting information, p. 3934 - 3936 (2016/08/16)
A facile method that allows for Ni(cod)2 to be used on the benchtop is reported. The procedure involves the preparation of paraffin-Ni(cod)2 capsules, which are stable to air and moisture. It is demonstrated that these readily available capsules can be used to promote a range of Ni(cod)2-catalyzed transformations. These studies are expected to promote the further use of Ni(cod)2 in organic synthesis.
