Palladium-Catalyzed Decarboxylative <i>Ortho</i>-Ethoxycarbonylation of <i>O</i>-Methyl Ketoximes and 2-Arylpyridines with Potassium Oxalate Monoester

Li, Zhongyuan; Wang, Guan‐Wu

doi:10.1021/acs.orglett.5b02422

Cited by 44 publications

(21 citation statements)

References 105 publications

(34 reference statements)

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“…In 2015, Wang et al. developed a Pd‐catalyzed ortho ethoxycarbonylation of O ‐methyl ketoximes with potassium oxalate monoester (Scheme ) . Various O ‐methyl ketoximes were employed in this protocol, affording the corresponding ethoxycarbonylation products in moderate to good yields (Scheme ).…”

Section: Oxime‐directed C–h Bond Activationmentioning

confidence: 99%

Transition Metal‐Catalyzed Reactions Involving Oximes

Zhang

et al. 2017

Adv Synth Catal

118

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Oximes are an easily prepared and transformed unit, which are widely used in organic synthesis. The oximes, including oxime ethers and esters, could realize various transformations, such as C–H bond activation, Heck‐type reactions, N–O bond cleavage/C–N bond formation, O–H bond cleavage and couplings. However, there is no a comprehensive review on this subject. Herein, we summarize the recent advances over the past 15 years in transition metal‐catalyzed reactions involving oximes, focusing on the reaction scope, limitations and mechanisms.

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Section: Oxime‐directed C–h Bond Activationmentioning

confidence: 99%

Transition Metal‐Catalyzed Reactions Involving Oximes

Zhang

et al. 2017

Adv Synth Catal

118

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“…[6] In 2008, Yu et al achieved the palladiumcatalyzed oxidative ethoxycarbonylation of arylpyridines using diethyl azodicarboxylate (DEAD) as an alkoxycarbonyl source. 7a Subsequently, a variety of carboxylating reagents, such as azodicarboxylates, [7] chlroformates, [8] oxaziridines, [9] glyoxalates, [10] α-keto esters, [11] dicarbonates, [12] formates, [13] potassium oxalates, [14] carbazates, [15] bromodifluoroacetates, [16] and tetrabromomethane [17] have been investigated. However, almost all the carboxylating reagents require the addition of a stoichiometric amount of additive, an oxidant or a base, for the formation of an alkoxyacyl radical and/or for the activation of inert CÀ H bonds, and these oxidant/base-mediated reactions suffer from several limitations such as toxic and inseparable byproducts, narrow substrate scope, and complicated experimental procedure.…”

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confidence: 99%

Rhodium‐Catalyzed Additive‐Free C−H Ethoxycarbonylation of (Hetero)Arenes with Diethyl Dicarbonate as a CO Surrogate

et al. 2021

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A rhodium-catalyzed C(sp 2 )-H ethoxycarbonylation of indoles and arylpyridines using diethyl dicarbonate was developed. The catalytic process features an additive-free ethoxycarbonylation reaction, in which only ethanol and CO 2 are produced as byproducts, providing a CO-free and operationally simple protocol. The introduced ethoxycarbonyl group is easily transformed into other ester and amide functionalities in a single step. Moreover, the reaction can be successfully applied on gram scale, and allows for the efficient synthesis of indole-2carboxylic acid esters and isophthalates.

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“…例如这些试剂往往毒性很大且操作不便, 或者缺乏环境友好性等. 我们课题组 [20] 曾报道了首例肟醚和 2-苯基吡啶导向的利用草酸单乙酯脱羧的碳−氢键酯基化反应. 基于我们课题组长期以来对碳−氢键活化的浓厚兴趣 [21] , 同时考虑到水杨酸衍生物在药物分子中的重要作用(图 1) [22] , 我们发展了一种新颖的钯催化的 2-苯氧基吡啶导向的酯基化反应.…”

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“…基于我们课题组长期以来对碳−氢键活化的浓厚兴趣 [21] , 同时考虑到水杨酸衍生物在药物分子中的重要作用(图 1) [22] , 我们发展了一种新颖的钯催化的 2-苯氧基吡啶导向的酯基化反应. [20,23] , 以高达 82%的产率生成了 3s. 综合以上邻位取代底物的产率, 我们可以看出对于这个反应位阻并不是影响反应效率的主要因素.…”

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Palladium-Catalyzed Decarboxylative Coupling of Potassium Oxalate Monoester with 2-Aryloxypyridines

Li¹,

Jing²,

Li³

et al. 2019

Acta Chim. Sinica

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Transition metal-catalyzed C-H activation has attracted extensive attention because of its excellent functional group tolerance and high efficiency. Among them, palladium-catalyzed reactions exhibit versatile catalytic cycles and have mild conditions compared to others. Therefore, the palladium-catalyzed C-H activation has been employed broadly as a practical strategy in synthetic chemistry during the past decade. Since the first example of palladium-catalyzed decarboxylative C-H acylation using α-oxocarboxylic acids was reported in 2008, a lot of substrates have been employed to synthesize acylated products due to the easily available α-oxocarboxylic acids as well as the importance of acylation. However, the transition metal-catalyzed C-H esterification via decarbonylation is still limited. Our group previously developed the first directed C-H esterification of methyl ketoximes and 2-phenylpyridines by using potassium oxalate monoester as the decarboxylative reagent. Encouraged by this impressive result as well as the importance of salicylate derivatives in drug discovery, herein we disclose the efficient palladium-catalyzed decarboxylative esterification of 2-aryloxpyridines. This reaction proceeds smoothly with potassium oxalate monoester, affording the desired products in moderate to good yields (50%～82%). Compared to our previous work, the electron-donating pyridinyloxy (PyO) group as the directing group and six-membered metallocycle intermediate dramatically enhance the practicability and substrate tolerance of the present method. In addition, one of the products has been chosen as the model compound to deprotect the directing group to get the valuable salicylate derivative. The present method not only provides an efficient and convenient protocol for the synthesis of ethyl salicylate derivatives, but also enriches the diversity of Pd(II)/Pd(IV) catalytic reactions. A general procedure for the esterification of 2-aryloxypyridines 1 with potassium oxalate monoester 2 is as following: a mixture of 1 (0.5 mmol), Pd(OAc) 2 (10 mol%), K 2 S 2 O 8 (1.0 mmol), Ag 2 CO 3 (1.0 mmol), 2 (1.0 mmol), D-CSA (0.125 mmol), and 1,4-dioxane (2.5 mL) in a 25 mL tube was heated at 80 ℃ for a suitable time. The reaction mixture was cooled to room temperature, and concentrated in vacuo. Purification of the residue by column chromatography on silica gel with petroleum ether and ethyl acetate as the eluent provided the desired product 3.

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Palladium-Catalyzed Decarboxylative Ortho-Ethoxycarbonylation of O-Methyl Ketoximes and 2-Arylpyridines with Potassium Oxalate Monoester

Cited by 44 publications

References 105 publications

Transition Metal‐Catalyzed Reactions Involving Oximes

Transition Metal‐Catalyzed Reactions Involving Oximes

Rhodium‐Catalyzed Additive‐Free C−H Ethoxycarbonylation of (Hetero)Arenes with Diethyl Dicarbonate as a CO Surrogate

Palladium-Catalyzed Decarboxylative Coupling of Potassium Oxalate Monoester with 2-Aryloxypyridines

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