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

Lakshman, Mahesh K.; Deb, Arghya; Chamala, Raghu Ram; Pradhan, Padmanava; Pratap, Ramendra

doi:10.1002/anie.201104035

Cited by 101 publications

(46 citation statements)

References 42 publications

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“…14–17 We have recently reported Ru-catalyzed C–H bond activation and arylation of 6-arylpurine 2′-deoxyribonucleosides under nonacidic conditions. 15 Acidic reaction media, which can be used in reactions of purines and ribonucleosides, are precluded due to the acid sensitivity of the glycosidic bond in the 2′-deoxyribonucleosides. More recently, C–H bond activation has been applied to the synthesis of polycycles containing fused purines and purine ribonucleosides, 16 and N-directed sulfonamidation of two purines as well as two purine ribonucleosides has been accomplished.…”

Section: Introductionmentioning

confidence: 99%

Purinyl N1-Directed Aromatic C–H Oxidation in 6-Arylpurines and 6-Arylpurine Nucleosides

et al. 2013

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Palladium-catalyzed C–H bond activation and oxidation of C6 arylpurines as well as C6 arylpurine nucleosides can be accomplished using Pd(OAc)2/PhI(OAc)2 in CH3CN. Despite the presence of four nitrogen atoms in the purine moiety as well as the polyoxygenated saccharide and a labile glycosidic bond in the nucleosides, these reactions can be effectively conducted. Notably, the generally more labile 2′-deoxyribonucleosides also undergo reaction. The reaction conditions can be tuned to yield either monoacetoxylated or diacetoxylated products predominantly. In the course of these investigations, a dimeric PdII-containing cyclopalladated C6 naphthylpurine derivative has been obtained and crystallographically characterized. This compound is competent in catalyzing the oxidization with PhI(OAc)2, indicating its plausible intermediacy in the chemistry. The X-ray structure of a monoacetoxylated product from this reaction has also been obtained.

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Section: Introductionmentioning

confidence: 99%

Purinyl N1-Directed Aromatic C–H Oxidation in 6-Arylpurines and 6-Arylpurine Nucleosides

et al. 2013

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“…Notably, even with arylated purine nucleosides (i.e., bearing sugar moieties), the direct C-H arylation with various aryl iodides proceeded. Lakshman [22] also reported a similar transformation using ruthenium catalysis.…”

Section: Various Directing Groupsmentioning

confidence: 81%

Biaryl Synthesis through Metal‐Catalyzed C–H Arylation

Yamaguchi

Itami

2013

Metal‐Catalyzed Cross‐Coupling Reactions and More

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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%

“…For this, we chose to evaluate Ru catalysis on the basis of the ortho -arylation reactions of C-6 aryl nucleosides using the purinyl nitrogen atom. 4 …”

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

Cited by 101 publications

References 42 publications

Purinyl N1-Directed Aromatic C–H Oxidation in 6-Arylpurines and 6-Arylpurine Nucleosides

Purinyl N1-Directed Aromatic C–H Oxidation in 6-Arylpurines and 6-Arylpurine Nucleosides

Biaryl Synthesis through Metal‐Catalyzed C–H Arylation

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

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