Is silver a mere terminal oxidant in palladium catalyzed C–H bond activation reactions?

Bhaskararao, Bangaru; Singh, Sukriti; Anand, Megha; Verma, Pritha; Prakash, P Wadgaonkar; Athira, C.; Malakar, Santanu; Schaefer, Henry F.; Sunoj, Raghavan B.

doi:10.1039/c9sc04540f

Cited by 57 publications

(40 citation statements)

References 42 publications

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“…This reaction is favored without the use of CO 2 or another transient directing group, we hypothesize, because chelation with the allyl group of the amine likely overcomes the formation of less reactive palladium diamine complexes. 76 The electron-rich Pd-species can then undergo oxidative addition to the aryl iodide to give VII , followed by reductive elimination to give the 3,3-diarylproduct VIII , which exchanges to give the minor Z -product. Because the reaction is performed with Ag I , some Pd 0 can be reoxidized to Pd II , 76 and as a result, both pathways are able to occur with similar rates throughout the reaction, as evidenced by the lack of change in the E / Z ratio throughout the reactions.…”

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confidence: 99%

“… 76 The electron-rich Pd-species can then undergo oxidative addition to the aryl iodide to give VII , followed by reductive elimination to give the 3,3-diarylproduct VIII , which exchanges to give the minor Z -product. Because the reaction is performed with Ag I , some Pd 0 can be reoxidized to Pd II , 76 and as a result, both pathways are able to occur with similar rates throughout the reaction, as evidenced by the lack of change in the E / Z ratio throughout the reactions. This also explains why the degradation of Pd II occurs throughout the reaction (see Figure 1 ).…”

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confidence: 99%

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Palladium-Catalyzed Regioselective Arylation of Unprotected Allylamines

Landge

Maxwell

Chand-Thakuri

et al. 2020

JACS Au

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Palladium-catalyzed organometallic transformations of free amines are often unsuccessful due to side reactions, such as oxidation, that can occur. However, the ability to furnish the free amine products from these reactions is important for improving the utility and sustainability of these processes, especially for accessing their potential as medicinal and agrochemical agents. Notably, the 3,3-diarylallylamine motif is prevalent in a variety of biologically relevant structures, yet there are few catalytic approaches to their synthesis, and none involving the free amine. Herein, we describe a simple protocol for the arylation of cinnamylamines and the diarylation of terminal allylamines to generate a diverse group of 3,3-diarylallylamine products using a Pd II precatalyst. Key features of the method are the ability to access relatively mild conditions that facilitate a broad substrate scope as well as direct diarylation of terminal allylamine substrates. In addition, several complex and therapeutically relevant molecules are included to demonstrate the utility of the transformation.

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confidence: 99%

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confidence: 99%

Palladium-Catalyzed Regioselective Arylation of Unprotected Allylamines

Landge

Maxwell

Chand-Thakuri

et al. 2020

JACS Au

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“…Previous studies have suggested that Ag additives can play many important roles in C-H functionalization reactions, for example, by serving as bases or halide scavengers [85,86], or as terminal oxidants [87]. More recently, it has also been proposed that the Ag might, in fact, have much deeper roles in the mechanisms of different C-H functionalization reactions, by for example enabling the formation of different bimetallic Ag-Pd species that constitutes key intermediates in their respective catalytic cycles [88][89][90].…”

Section: Methodsmentioning

confidence: 99%

Synthesis of Elaborate Benzofuran-2-Carboxamide Derivatives through a Combination of 8-Aminoquinoline Directed C–H Arylation and Transamidation Chemistry

et al. 2020

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Herein, we present a short and highly modular synthetic route that involves 8-aminoquinoline directed C–H arylation and transamidation chemistry, and which enables access to a wide range of elaborate benzofuran-2-carboxamides. For the directed C–H arylation reactions, Pd catalysis was used to install a wide range of aryl and heteroaryl substituents at the C3 position of the benzofuran scaffold in high efficiency. Directing group cleavage and further diversification of the C3-arylated benzofuran products were then achieved in a single synthetic operation through the utilization of a one-pot, two-step transamidation procedure, which proceeded via the intermediate N-acyl-Boc-carbamates. Given the high efficiency and modularity of this synthetic strategy, it constitutes a very attractive method for generating structurally diverse collections of benzofuran derivatives for small molecule screening campaigns.

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“…7). Given a recent report from Sunoj's team [24], the silver salt could be more than a terminal oxidant, forming a Pd/Ag heterobimetallic species which would participate in the catalytic cycle.…”

Section: Introductionmentioning

confidence: 99%

Pd-catalyzed Intermolecular Dehydrogenative Heck Reactions of Six-membered Heteroarenes

Bras

Мuzart

2021

COC

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: The PdII-mediated cross-coupling of (hetero)arenes with alkenes may be an effective method for the formation of a C–C bond from two C–H bonds. Discovered by Fujiwara and co-workers in 1967, this reaction led to a number of reports that we firstly highlighted in 2011 (review with references till June 2010) and for which, we retained the name “dehydrogenative Heck reaction” (DHR). The DHR of six-membered heteroarenes, has been the subject of intensive research over the last ten years. The present review is limited to these dehydrogenative Heck reactions published since 2010, underlining the diversity of the procedures and, with personal comments, the mechanisms and intermediates that have been proposed.

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Is silver a mere terminal oxidant in palladium catalyzed C–H bond activation reactions?

Abstract: We disclose an intriguing and a potentially general role for one of the most commonly used silver salt additives whose molecular understanding continues to remain rather vague in the contemporary practice of palladium catalysis.

Cited by 57 publications

References 42 publications

Palladium-Catalyzed Regioselective Arylation of Unprotected Allylamines

Palladium-Catalyzed Regioselective Arylation of Unprotected Allylamines

Synthesis of Elaborate Benzofuran-2-Carboxamide Derivatives through a Combination of 8-Aminoquinoline Directed C–H Arylation and Transamidation Chemistry

Pd-catalyzed Intermolecular Dehydrogenative Heck Reactions of Six-membered Heteroarenes

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