Pd(II)-Catalyzed <i>Ortho</i> Arylation of 6-Arylpurines with Aryl Iodides via Purine-Directed C−H Activation: A New Strategy for Modification of 6-Arylpurine Derivatives

Guo, Hai‐Ming; Jiang, Lili; Niu, Hong‐Ying; Rao, Wei‐Hao; Liu, Liang; Mao, Runze; Li, De-Yang; Qu, Gui‐Rong

doi:10.1021/ol200405w

Cited by 71 publications

(26 citation statements)

References 61 publications

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“…In contrast to the reactions reported here, those catalyzed by Pd required 30 equiv of aryl iodides, with reaction times from 48 h (nucleosides) to 60 h (purines), at 120 °C. [12] Thus, the present conditions are substantially more conservative on the aryl halide and generally provide faster reactions. Pd catalysis produces only monoarylation, [12] plausibly due to slow reactions, whereas under Ru catalysis both mono and diaryl products are formed.…”

mentioning

confidence: 97%

“…[12] It is therefore reasonable to offer a comparison of the two approaches. In contrast to the reactions reported here, those catalyzed by Pd required 30 equiv of aryl iodides, with reaction times from 48 h (nucleosides) to 60 h (purines), at 120 °C.…”

mentioning

confidence: 99%

“…[12] Thus, the present conditions are substantially more conservative on the aryl halide and generally provide faster reactions. Pd catalysis produces only monoarylation, [12] plausibly due to slow reactions, whereas under Ru catalysis both mono and diaryl products are formed. Use of AcOH as solvent at 120 °C and N 2 atmosphere have been stated as crucial for the Pd-catalyzed reactions.…”

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confidence: 99%

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Direct Arylation of 6‐Phenylpurine and 6‐Arylpurine Nucleosides by Ruthenium‐Catalyzed CH Bond Activation

et al. 2011

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Direct Arylation of 6‐Phenylpurine and 6‐Arylpurine Nucleosides by Ruthenium‐Catalyzed CH Bond Activation

et al. 2011

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“…In 2011, efforts by others 33 and by us 34 led to the knowledge that the embedded purinyl nitrogen atoms can be used to direct C–H bond activation at remote sites in nucleosides. Both Pd(OAc) 2 and (ArRuCl 2 ) 2 catalysts were effective.…”

Section: Purinyl N-directed C–h Bond Oxidation Using Pidamentioning

confidence: 99%

When nucleoside chemistry met hypervalent iodine reagents

Lakshman

Zajc

2017

Arkivoc

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There has been increasing use of hypervalent iodine reagents in the field of nucleoside chemistry. Applications span: (a) synthesis of nucleoside analogues with sulfur and seleno sugar surrogates, (b) synthesis of unusual carbocyclic and ether ring-containing nucleosides, (c) introduction of sulfur and selenium into pyrimidine bases of nucleosides and analogues, (d) synthesis of isoxazole and isoxazoline ring-containing nucleoside analogues, (e) involvement of purine ring nitrogen atoms for remote C–H bond oxidation, and (f) metal-catalyzed and uncatalyzed synthesis of benzimidazolyl purine nucleoside analogues by intramolecular C–N bond formation. This review offers a perspective on developments involving the use of hypervalent iodine reagents in the field of nucleoside chemistry that have appeared in the literature in the 2003–2017 time frame.

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“…2 Within the context of nucleoside and purine modification, we 3,4 and others 5,6 have utilized the embedded purinyl nitrogen atoms to accomplish remote functionalizations of aromatic rings. In general, C–H bond activation has now become an important approach to late-stage functionalization of the labile polynitrogenated nucleosides and related heterocycles in ways that are otherwise not trivial.…”

Section: Introductionmentioning

confidence: 99%

Ruthenium-Catalyzed C–H Bond Activation Approach to Azolyl Aminals and Hemiaminal Ethers, Mechanistic Evaluations, and Isomer Interconversion

et al. 2016

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C(sp3)–N bond-forming reactions between benzotriazole and 5,6-dimethylbenzotriazole with N-methylpyrrolidinone, tetrahydrofuran, tetrahydropyran, diethyl ether, 1,4-dioxane, and isochroman have been conducted using RuCl3•3H2O/t-BuOOH in 1,2-dichloroethane. In all cases, N1 and N2 alkylation products were obtained, and these are readily separated by chromatography. One of these products, 1-(isochroman-1-yl)-5,6-dimethyl-1H-benzotriazole, was examined by X-ray crystallography. It is the first such compound to be analyzed by this method, and notably, the benzotriazolyl moiety is quasi-axially disposed, consistent with the anomeric effect. This has plausible consequences, not observed previously. In contrast to other hemiaminal ether-forming reactions, which proceed via radicals, this Ru-catalyzed process is not suppressed in the presence of a radical inhibitor. Therefore, an oxoruthenium-species-mediated rapid formation of an oxocarbenium intermediate is believed to occur. In the radical-trapping experiment, previously unknown products containing both the benzotriazole and the TEMPO unit have been identified. In these products, it is likely that the benzotriazole is introduced via a Ru-catalyzed C–N bond formation, whereas C–O bond-formation with TEMPO occurs via a radical reaction. We show that reactions of THF with TEMPO are influenced by ambient light. A competitive reaction of THF and THF-d8 with benzotriazole indicated that C–H bond cleavage occurs ca. 5 times faster than C–D cleavage. This is comparable to other metal-mediated radical reactions of THF, but lower than that observed for a reaction catalyzed by n-Bu4N+I−. Detailed mechanistic experiments and comparisons are described. The catalytic system was also evaluated for reactions of benzimidazole, imidazole, 1,2,4-triazole, and 1,2,3-triazole with THF, and successful reactions were achieved in each case. In the course of our studies, we discovered an unexpected but significant isomerization of some of the benzotriazolyl hemiaminal ethers. This is plausibly attributable to the pseudoaxial orientation of the heterocycle in the products and the stability of oxocarbenium ions, both of which can contribute to C–N bond cleavage and reformation. Predominantly, the N2-isomers rearrange to the N1-isomers even upon storage at low temperature! This previously unknown phenomenon has also been studied and described.

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Pd(II)-Catalyzed Ortho Arylation of 6-Arylpurines with Aryl Iodides via Purine-Directed C−H Activation: A New Strategy for Modification of 6-Arylpurine Derivatives

Cited by 71 publications

References 61 publications

Direct Arylation of 6‐Phenylpurine and 6‐Arylpurine Nucleosides by Ruthenium‐Catalyzed CH Bond Activation

Direct Arylation of 6‐Phenylpurine and 6‐Arylpurine Nucleosides by Ruthenium‐Catalyzed CH Bond Activation

When nucleoside chemistry met hypervalent iodine reagents

Ruthenium-Catalyzed C–H Bond Activation Approach to Azolyl Aminals and Hemiaminal Ethers, Mechanistic Evaluations, and Isomer Interconversion

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