62931-24-2Relevant academic research and scientific papers
Nickel-Catalyzed Aminoxylation of Inert Aliphatic C(sp3)-H Bonds with Stable Nitroxyl Radicals under Air: One-Pot Route to α-Formyl Acid Derivatives
Wang, Chunxia,Zhang, Luoqiang,You, Jingsong
, p. 1690 - 1693 (2017)
Nickel-catalyzed aminoxylation of an unactivated C(sp3)-H bond with a stable nitroxyl radical has been accomplished for the first time to offer various N-alkoxyamine derivatives, which further enables a one-pot approach to α-formyl acid derivatives. The aminoxylation process reported also provides direct evidence for the oxidative addition of a cyclometallic intermediate with a free radical, which is helpful for the reaction-mechanism study in transition-metal-catalyzed functionalization of inert C(sp3)-H bonds.
Mechanism of 8-Aminoquinoline-Directed Ni-Catalyzed C(sp3)-H Functionalization: Paramagnetic Ni(II) Species and the Deleterious Effect of Carbonate as a Base
Liu, Junyang,Johnson, Samuel A.
, p. 2970 - 2982 (2021/06/28)
Studies into the mechanism of 8-aminoquinoline-directed nickel-catalyzed C(sp3)-H arylation with iodoarenes were carried out, to determine the catalyst resting state and optimize catalytic performance. Paramagnetic complexes undergo the key C-H activation step. The ubiquitous base Na2CO3is found to hinder catalysis; replacement of Na2CO3with NaOtBu gave improved catalytic turnovers under milder conditions. Deprotonation of the 8-aminoquinoline derivativeN-(quinolin-8-yl)pivalamide (1a) at the amide nitrogen using NaH, followed by reaction with NiCl2(PPh3)2allowed for the isolation of complex Ni([AQpiv]-κN,N)2(3) with chelating N-donors (where [AQpiv] = C9NH6NCOtBu). Complex3is a four-coordinate disphenoidal high-spin Ni(II) complex, excluding short anagostic Ni-tBu hydrogen interactions. Complex3reacts with the paddle-wheel [Ph3PNi(μ-CO2tBu)2]2(6·PPh3) ortBuCO2H to give insoluble {[AQpiv]Ni(O2CtBu)}2(5). Dissolution of5in donor solvents L (L= DMSO and DMF) gave a paramagnetic intermediate assigned by NMR as [AQpiv]Ni(O2CtBu)L (5·L) and equilibrium reformation of3and6·L. DFT calculations support this equilibrium in solution. Both3and5undergo C-H activation at temperatures as low as 80 °C and in the presence of PR3(PR3= PPh3, PiBu3) to give Ni(C9NH6NCOCMe2CH2-κN,N,C)PR3(7·PR3). The C-H functionalization reaction orders with respect to7·PiBu3, iodoarenes, and phosphines were determined. Hammett analysis using electronically different aryl iodides suggests a concerted oxidative addition mechanism for the C-H functionalization step; DFT calculations were also carried out to support this finding. When Na2CO3is used as the base, the rate determination step for C-H functionalization appears to be 8-aminoquinoline deprotonation and binding to Ni. The carbonate anion was also observed to provide a deleterious NMR-inactive low-energy off-cycle resting state in catalysis. Replacement of Na2CO3with NaOtBu improved catalysis at milder conditions and made carboxylic acid and phosphine additives unnecessary. Complex3and its functionalized analogues were observed as the catalyst resting state under these conditions.
Copper-Catalyzed Oxidative Benzylic C(sp3)?H Cyclization for the Synthesis of β-Lactams
Nozawa-Kumada, Kanako,Saga, Satoshi,Matsuzawa, Yuta,Hayashi, Masahito,Shigeno, Masanori,Kondo, Yoshinori
supporting information, p. 4496 - 4499 (2020/04/10)
β-Lactams are important structural motifs because of their ubiquity in natural products and pharmaceuticals. We report herein a Cu-catalyzed intramolecular oxidative C(sp3)?H amidation for the synthesis of β-lactams using tBuOOtBu. This method
Pd/Cu-Catalyzed Cascade C(sp3)-H Arylation and Intramolecular C-N Coupling: A One-Pot Synthesis of 3,4-2 H-Quinolinone Skeletons
Xiao, Han-Zhi,Wang, Wen-Shu,Sun, Yu-Song,Luo, Hao,Li, Bo-Wen,Wang, Xiao-Dong,Lin, Wei-Li,Luo, Fei-Xian
supporting information, p. 1668 - 1671 (2019/03/11)
In this letter, we successfully explored a cascade Pd/Cu-catalyzed intermolecular C(sp3)-H arylation of amides and intramolecular C-N coupling reaction. This method provides a one-pot strategy to synthesize 3,4-2H-quinolinone with good regioselectivity of C-H arylation and C-N coupling from C-I and C-X bonds from readily available starting materials.
Palladium-catalyzed 2-pyridylmethyl-directed β-C(sp3)–H activation and cyclization of aliphatic amides with gem-dibromoolefins: A rapid access to γ-lactams
Zhou, Danni,Wang, Chunxia,Li, Mingliang,Long, Zheng,Lan, Jingbo
, p. 191 - 193 (2017/11/17)
The direct Pd-catalyzed β-C(sp3)–H activation and cyclization of aliphatic amides bearing a removable 2-pyridylmethyl directing group with gem-dibromoolefins is described for the first time to construct a variety of γ-lactams. The resulting products with Z- and E-configurations can be easily separated and purified after the reaction, demonstrating the effectiveness and applicability of the method herein developed.
Nickel-catalysed direct alkylation of thiophenes via double C(sp3)-H/C(sp2)-H bond cleavage: The importance of KH2PO4
Wang, Xie,Xie, Peipei,Qiu, Renhua,Zhu, Longzhi,Liu, Ting,Li, You,Iwasaki, Takanori,Au, Chak-Tong,Xu, Xinhua,Xia, Yuanzhi,Yin, Shuang-Feng,Kambe, Nobuaki
, p. 8316 - 8319 (2017/07/26)
A Ni-catalyzed oxidative C-H/C-H cross-dehydrogenative coupling (CDC) reaction was developed for constructing various highly functionalized alkyl (aryl)-substituted thiophenes. This method employs thiophenes and aliphatic (aromatic) amides that contain an 8-aminoquinoline as a removable directing group in the presence of a silver oxidant. The approach enables the facile one-step synthesis of substituted thiophenes with high functional group compatibility via double C-H bond cleavage without affecting C-Br and C-I bonds. DFT calculations verify the importance of KH2PO4 as an additive for promoting C-H bond cleavage and support the involvement of a Ni(iii) species in the reaction.
Copper(II)-mediated intermolecular amination of inert C(sp3)[sbnd]H bonds with simple alkylamines to construct α,α-disubstituted β-amino acid derivatives
Wang, Chunxia,Yang, Yudong
supporting information, p. 935 - 940 (2017/02/18)
Disclosed herein is a copper(II)-mediated chelation-assisted intermolecular amination of inert C(sp3)[sbnd]H bonds using simple alkylamines as the amino source. A straightforward and step-economic alternative to α,α-disubstituted β-amino acid derivatives is provided consequently. This reaction features good functional group tolerance and relatively broad substrate scope. Furthermore, a coupling product between morpholine and radical inhibitor 2,6-di-tert-butyl-p-cresol (BHT) was isolated, indicating that a single electron transfer (SET) process might be involved in this transformation.
Difluoromethylation of carboxylic acids via the addition of difluorinated phosphorus ylide to acyl chlorides
Trifonov, Alexey L.,Levin, Vitalij V.,Struchkova, Marina I.,Dilman, Alexander D.
supporting information, p. 5304 - 5307 (2017/11/06)
A one-step protocol for the difluoromethylation of carboxylic acids is described. The reaction involves the interaction of intermediate acyl chlorides with in situ generated difluorinated phosphorus ylide Ph3P=CF2. Aromatic acids can be selectively transformed within one step either to bis-difluoromethylated alcohols or to difluorinated ketones depending on the particular reaction conditions. For bulky α-branched carboxylic acids, only ketones are produced.
Thioamide-Directed Cobalt(III)-Catalyzed Selective Amidation of C(sp3)?H Bonds
Tan, Peng Wen,Mak, Adrian M.,Sullivan, Michael B.,Dixon, Darren J.,Seayad, Jayasree
supporting information, p. 16550 - 16554 (2017/12/07)
A mild, oxidant-free, and selective Cp*CoIII-catalyzed amidation of thioamides with robust dioxazolone amidating agents via C(sp3)?H bond activation to generate the desired amidated products is reported. The method is efficient and allows for the C?H amidation of a wide range of functionalized thioamides with aryl-, heteroaryl-, and alkyl-substituted dioxazolones under the Cp*CoIII-catalyzed conditions. The observed regioselectivity towards primary C(sp3)?H activation is supported by computational studies and the cyclometalation is proposed to proceed by means of an external carboxylate-assisted concerted metalation/deprotonation mechanism. The reported method is a rare example of the use of a directing group other than the commonly used pyridine and quinolone classes for Cp*CoIII-catalyzed C(sp3)?H functionalization and the first to exploit thioamides.
A C-H Insertion Approach to Functionalized Cyclopentenones
Wang, Youliang,Zarca, Maxence,Gong, Liu-Zhu,Zhang, Liming
, p. 7516 - 7519 (2016/07/06)
Cyclopentenones are synthetically versatile structures, and their straightforward construction from alkynone substrates by employing synthetically streamlining C-H insertion is conceptually appealing and of high synthetic potential. But, its implementation is very limited. Herein we report a Au-catalyzed version, which affords 2-bromocyclopent-2-en-1-ones with a broad scope and synthetically desirable diastereoselectivities. The proposed key intermediate capable of the observed insertion into unactivated C-H bonds is a fully functionalized gold vinylidene, which is generated via a novel intermolecular strategy. This flexible access of likely gold vinylidenes opens various opportunities to explore their versatile reactivities.
