Facile syntheses of 3,4-disubstituted pyrroline nitroxides and their further synthetic applications

Úr, Györgyi; Kálai, Tamás; Hideg, Kálmán

doi:10.1016/j.tetlet.2016.01.012

Cited by 11 publications

(8 citation statements)

References 16 publications

(9 reference statements)

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“…Our efforts to construct a P-C bond with diethylphospite via the Pd-catalyzed Hirao reaction with the conventional or microwave-assisted method [42] also failed. As a result, we finally decided to lithiate [43] the O-methyl derivative 16, as achieved via Fenton reaction in a dimethylsulfoxide/H 2 O 2 /Fe 2+ system [44], followed by treatment with 1.0 eq. BuLi (buthyl lithium) and addition of diethylchlorophosphate to produce the diamagnetic vinyl phosphonate, which was not isolated but the crude product was treated with meta-chloroperoxybenzoic acid [45].…”

Section: Phosphonate Synthesis With Lithiationmentioning

confidence: 99%

Syntheses and Reactions of Pyrroline, Piperidine Nitroxide Phosphonates

et al. 2020

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Organophosphorus compounds occupy a significant position among the plethora of organic compounds, but a limited number of paramagnetic phosphorus compounds have been reported, including paramagnetic phosphonates. This paper describes the syntheses and further transformations of pyrroline and piperidine nitroxide phosphonates by well-established methods, such as the Pudovik, Arbuzov and Horner-Wadsworth-Emmons (HWE) reactions. The reaction of paramagnetic α-bromoketone produced a vinylphosphonate in the Perkow reaction. Paramagnetic α-hydroxyphosphonates could be subjected to oxidation, elimination and substitution reactions to produce various paramagnetic phosphonates. The synthesized paramagnetic phosphonates proved to be useful synthetic building blocks for carbon-carbon bond-forming reactions in the Horner-Wadsworth-Emmons olefination reactions. The unsaturated compounds achieved could be transformed into various substituted pyrroline nitroxides, proxyl nitroxides and paramagnetic polyaromatics. The Trolox® equivalent antioxidant capacity (TEAC) of new phosphonates was also screened, and tertiary α-hydroxyphosphonatate nitroxides exhibited remarkable antioxidant activity.

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Section: Phosphonate Synthesis With Lithiationmentioning

confidence: 99%

Syntheses and Reactions of Pyrroline, Piperidine Nitroxide Phosphonates

et al. 2020

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“…This monoester was converted to an acyl azide by diphenylphosporyl azide (DPPA) followed by a Curtius rearrangement and treatment with 2-nitrobenzylamine furnished urethane, which was not isolated. Cyclization of the crude urethane by KOt-Bu offered N-2-nitrobenzyl-protected uracyl 239, deprotection of which with UV irradiation or with excess KOt-Bu yielded 5,5,7,7-tetramethyl-6,7-dihydro-1H-pyrrolo[3,4-d]pyrimidine-2,4(3H,5H)-dione-5-yloxyl, e.g., spin labeled uracyl 240 [93] (Scheme 43).…”

Section: Nitroxides Fused With Six-membered Het-erocyclesmentioning

confidence: 99%

Synthesis and Application of Stable Nitroxide Free Radicals Fused with Carbocycles and Heterocycles

Bognár

Úr

Sár

et al. 2019

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Stable nitroxide free radicals have traditionally been associated with 2,2,6,6- tetramethylpiperidine-1-oxyl (TEMPO) or its 4-substituted derivatives as relatively inexpensive and readily accessible compounds with limited possibilities for further chemical modification. Over the past two decades, there has been a resurgence of interest in stable free radicals with proper functionalization tuned for various applications. The objective of this review is to present recent results with synthetic methodologies to achieve stable nitroxide free radicals fused with aromatic carbocycles and heterocycles. There are two main approaches for accessing stable nitroxide free radicals fused with arenes, e.g., isoindoline- like nitroxides: further functionalization and oxidation of phthalimide or inventive functionalization of pyrroline nitroxide key compounds. The latter also offers the constructions of versatile heterocyclic scaffolds (furan, pyrrole, thiophene, 1,2-thiazole, selenophene, pyrazole, pyrimidine, pyridine, pyridazine, 1,5-benzothiazepine) that are fused with pyrroline or tetrahydropyridine nitroxide rings. The possible applications of these new stable nitroxide free radicals, such as covalent spin labels and noncovalent spin probes of proteins and nucleic acids, profluorescent probes, building blocks for construction of dual active drugs and electroactive materials, and substances for controlled free radical polymerization, are discussed.

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“…As compound 6 is not available via Favorskii rearrangement, 13 its synthesis was recently reported via the deprotonation of an α,β-unsaturated ester with the Li salt of 2,2,6,6-tetramethylpiperidine (LTMP) followed by treatment with the electrophile I 2 . 16 In this paper, we report further transformations of compound 6, avoiding dehalogenation, and its Sonogashira and Buchwald-Hartwig coupling reactions. The findings involving compound 6 inspired us to evaluate further reactions of more readily available compounds 1, 2, and 3.…”

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confidence: 95%

“…Consequently, our laboratory has synthesized several entirely carbon-based biomolecule-nitroxide-containing adducts, such as spin-labeled amino acids, 8 spin-labeled uracil, 9 spin-labeled resveratrol derivatives 10 and spin-labeled drugs. 11,12 It was essential to develop a series of paramagnetic vinyl bromides (1, 13 2, 14 and 3 13 ) and iodides (4, 15 5, 15 and 6 16 ) as useful substrates for Pd-catalyzed cross-coupling reac-tions ( Figure 1). As compound 6 is not available via Favorskii rearrangement, 13 its synthesis was recently reported via the deprotonation of an α,β-unsaturated ester with the Li salt of 2,2,6,6-tetramethylpiperidine (LTMP) followed by treatment with the electrophile I 2 .…”

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confidence: 99%

Palladium- and/or Copper-Catalyzed Cross-Coupling Reactions of Paramagnetic Vinyl Bromides and Iodides

et al. 2017

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A series of new 3-substituted-4-iodo-(2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrol-1-yl)oxidanyl compounds is synthesized to achieve NH2- and SH-specific spin labels. The new vinyl iodides are tested in Sonogashira and Buchwald–Hartwig cross-coupling reactions to produce a paramagnetic β-amino acid ester, pyrroline nitroxide-condensed heterocycles, including a paramagnetic α,α′-dipyridyl ligand and a spin-labeled sulfonamide.

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Facile syntheses of 3,4-disubstituted pyrroline nitroxides and their further synthetic applications

Cited by 11 publications

References 16 publications

Syntheses and Reactions of Pyrroline, Piperidine Nitroxide Phosphonates

Syntheses and Reactions of Pyrroline, Piperidine Nitroxide Phosphonates

Synthesis and Application of Stable Nitroxide Free Radicals Fused with Carbocycles and Heterocycles

Palladium- and/or Copper-Catalyzed Cross-Coupling Reactions of Paramagnetic Vinyl Bromides and Iodides

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