Oxidative cyclization in the synthesis of 5‐ and 6‐membered <i>N</i>,<i>O</i>‐heterocycles

Tsoungas, Petros G.; Diplas, Andreas I.

doi:10.1002/hc.10200

Cited by 11 publications

(5 citation statements)

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“…Oxidants, such as the one-electron lead(IV) acetate (LTA) or the two-electron, I(III) reagents phenyliodine diacetate (PIDA) and phenyliodine bis(trifluoroacetate) (PIFA) or I(V) reagent Dess-Martin periodinane (DMP), operating by the ligand coupling mechanism, [30] are commonly used in ring cyclizations. [31,32] On the other hand, the use of transition metal (TM) oxides, like AgO (or Ag 2 O), has certain advantages over non-TMs, such as multiple oxidation states, coordination potential and some d with s and p orbital hybridization. [33] Their oxidant profile, depends on the structure to be oxidized and the relative MÀ O (M: Ag, Pb) bond dissociation enthalpy (BDE) of the transiently generated organoelement complex.…”

Section: D-a Self Cycloaddition-formation Of Spiro Adductmentioning

confidence: 99%

Self Cycloaddition of o‐Naphthoquinone Nitrosomethide to (±) Spiro{naphthalene(naphthopyranofurazan)}‐one Oxide: An Insight into its Formation

et al. 2022

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2-Hydroxy-1-naphthaldehyde oxime was oxidized by AgO (or Ag 2 O), in presence of N-methyl morpholine N-oxide (NMMO), to the title spiro adduct-dimer (�)-Spiro{naphthalene-1(2H),4'-(naphtho[2',1':2,3]pyrano[4,5-c]furazan)}-2-one-11'-oxide by a Diels-Alder(DÀ A) type self-cycloaddition, through the agency of an o-naphthoquinone nitrosomethide (o-NQM). Moreover, 2hydroxy-8-methoxy-1-naphthaldehyde oxime was prepared and subjected to the same oxidation conditions. Its sterically guided result, 9-methoxynaphtho[1,2-d]isoxazole, was isolated, instead of the expected spiro adduct. The peri intramolecular H bonding in the oxime is considered to have a key contribution to the outcome. Geometry and energy features of the oxidant-and stereo-guided selectivity of both oxidation outcomes have been explored by DFT, perturbation theory and coupled cluster calculations. The reaction free energy of the DÀ A intermolecular cycloaddition is calculated at À 82.0 kcal/mol, indicating its predominance over the intramolecular cyclization of ca. À 37.6 kcal/mol. The cycloaddition is facilitated by NMMO through dipolar interactions and hydrogen bonding with both metal complexes and o-NQM. The 8(peri)-OMe substitution of the reactant oxime sterically impedes formation of the spiro adduct, instead it undergoes a more facile cyclodehydration to the isoxazole structure by ca. 4.9 kcal/mol.

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Section: D-a Self Cycloaddition-formation Of Spiro Adductmentioning

confidence: 99%

Self Cycloaddition of o‐Naphthoquinone Nitrosomethide to (±) Spiro{naphthalene(naphthopyranofurazan)}‐one Oxide: An Insight into its Formation

et al. 2022

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“…Corresponding pyrazole 3i was isolated as a by‐product. Oxidative cyclization of hydrazones to pyrazoles by number of oxidative agents (Pb(OAc) 4 , hypervalent iodine compounds, MnO 2 …) is described in the literature [22–24]. An oxidative agent in the case of formation of pyrazoles 3 is unclear; it could be the second molecule of diazonium salt.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and characterization of some 3‐acyl‐4‐amino‐1‐aryl‐1H‐pyrazoles

Šimůnek

Svobodová

Macháček

2009

Journal of Heterocyclic Chem

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Online risk prediction tools for common cancers are now easily accessible and widely used by patients and doctors for informed decision‐making concerning screening and diagnosis. A practical problem is as cancer research moves forward and new biomarkers and risk factors are discovered, there is a need to update the risk algorithms to include them. Typically, the new markers and risk factors cannot be retrospectively measured on the same study participants used to develop the original prediction tool, necessitating the merging of a separate study of different participants, which may be much smaller in sample size and of a different design. Validation of the updated tool on a third independent data set is warranted before the updated tool can go online. This article reports on the application of Bayes rule for updating risk prediction tools to include a set of biomarkers measured in an external study to the original study used to develop the risk prediction tool. The procedure is illustrated in the context of updating the online Prostate Cancer Prevention Trial Risk Calculator to incorporate the new markers %freePSA and [‐2]proPSA measured on an external case–control study performed in Texas, U.S.. Recent state‐of‐the art methods in validation of risk prediction tools and evaluation of the improvement of updated to original tools are implemented using an external validation set provided by the U.S. Early Detection Research Network.

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“…The simplest method was reported by Freitas et al in which they performed a simple cyclodehydration reaction of nitroketoximes 1 to create 1,2,5‐oxadiazole‐N‐oxides 2 (Scheme 1) (Freitas et al, 2023). Tsoungas and Diplas (2003) also presented another simple method in which dioximes 2 underwent cyclization in the presence of sodium hydroxide and sodium hypochlorite to yield 1,2,5‐oxadiazole‐N‐oxides 3 (Scheme 2).…”

Section: Synthetic Strategies For 125‐oxadiazole and Its Derivativesmentioning

confidence: 99%

Synthetic approaches and applications of an underprivileged 1,2,5‐oxadiazole moiety: A review

Kumar

Mazumder

et al. 2023

Chem Biol Drug Des

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Abstract1,2,5‐oxadiazole belongs to five‐membered heterocyclic compounds with two nitrogen and one oxygen atom. In comparison with other heterocyclic moieties, 1,2,5‐oxadiazoles moiety is considered as underprivileged as it attracted little attention of the researchers although lot of scopes and possible applications in medicinal, material and agriculture science. 1,2,5‐oxadiazole and its derivatives have been reported as good pharmacophores as carbonic anhydrase inhibitors, antibacterial, vasodilating agents, antimalarial, anticancer, etc. In the presented manuscript, we reviewed granted patents and different synthetic strategies which have been reported for the synthesis of 1,2,5‐oxadiazoles such as cycloaddition, dimerization, cyclodehydration, condensation, thermolysis, nitration, oxidation and ring‐conversion. These synthetic methods have also been analysed for their merits and demerits. The manuscript also highlighted various applications of 1,2,5‐oxadiazole and its derivatives. We hope that researchers across the scientific streams will be benefitted from the presented review articles for designing their work related to 1,2,5‐oxadiazoles.

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Oxidative cyclization in the synthesis of 5‐ and 6‐membered N,O‐heterocycles

Abstract: The versatility and potential of oxidative cyclization in the synthesis of 5-and 6-membered N-and/or O-heterocycles is presented through judiciously selected examples.

Cited by 11 publications

References 314 publications

Self Cycloaddition of o‐Naphthoquinone Nitrosomethide to (±) Spiro{naphthalene(naphthopyranofurazan)}‐one Oxide: An Insight into its Formation

Self Cycloaddition of o‐Naphthoquinone Nitrosomethide to (±) Spiro{naphthalene(naphthopyranofurazan)}‐one Oxide: An Insight into its Formation

Synthesis and characterization of some 3‐acyl‐4‐amino‐1‐aryl‐1H‐pyrazoles

Synthetic approaches and applications of an underprivileged 1,2,5‐oxadiazole moiety: A review

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