Oxazolones

Rao, Yong; Filler, Robert

doi:10.1002/9780470187289.ch3

Cited by 26 publications

(6 citation statements)

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“…The oxazolones 1a – 1m shown in Figure 2 have been prepared by the classical Erlenmeyer–Plöchl method, 12 while the hippuric acids have been prepared by the Schotten–Baumann method. 13 Oxazolones 1a – 1d and 1f – 1h appear on SciFinder, 14 while 1e and 1i – 1m are new species.…”

Section: Resultsmentioning

confidence: 99%

“…In addition, one solution of compounds 4d and 3h as representative examples was deoxygenated by passing argon through it, and the value of the QY was redetermined to check the influence of O 2 in the intensity of the luminescence. The oxazolones 1a – 1m were prepared using the Erlenmeyer–Plöchl method, by reaction of the corresponding hippuric acids and aldehydes in acetic anhydride . The hippuric acids were prepared by the Schotten–Baumann method …”

Section: Methodsmentioning

confidence: 99%

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Fluorescence Amplification of Unsaturated Oxazolones Using Palladium: Photophysical and Computational Studies

et al. 2023

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Weakly fluorescent (Z)-4-arylidene-5-(4H)-oxazolones (1), ΦPL < 0.1%, containing a variety of conjugated aromatic fragments and/or charged arylidene moieties, have been orthopalladated by reaction with Pd(OAc)2. The resulting dinuclear complexes (2) have the oxazolone ligands bonded as a C^N-chelate, restricting intramolecular motions involving the oxazolone. From 2, a variety of mononuclear derivatives, such as [Pd(C^N-oxazolone)(O2CCF3)(py)] (3), [Pd(C^N-oxazolone)(py)2](ClO4) (4), [Pd(C^N-oxazolone)(Cl)(py)] (5), and [Pd(C^N-oxazolone)(X)(NHC)] (6, 7), have been prepared and fully characterized. Most of complexes 3–6 are strongly fluorescent in solution in the range of wavelengths from green to yellow, with values of ΦPL up to 28% (4h), which are among the highest values of quantum yield ever reported for organometallic Pd complexes with bidentate ligands. This means that the introduction of the Pd in the oxazolone scaffold produces in some cases an amplification of the fluorescence of several orders of magnitude from the free ligand 1 to complexes 3–6. Systematic variations of the substituents of the oxazolones and the ancillary ligands show that the wavelength of emission is tuned by the nature of the oxazolone, while the quantum yield is deeply influenced by the change of ligands. TD-DFT studies of complexes 3–6 show a direct correlation between the participation of the Pd orbitals in the HOMO and the loss of emission through non-radiative pathways. This model allows the understanding of the amplification of the fluorescence and the future rational design of new organopalladium systems with improved properties.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Fluorescence Amplification of Unsaturated Oxazolones Using Palladium: Photophysical and Computational Studies

et al. 2023

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“…We present here the synthesis of ortho-palladated unsaturated 5(4 H )-oxazolones. These compounds are relevant organic precursors and intermediates in the preparation of heterocyclic compounds of pharmacological interest, more specifically in the synthesis of amino acids . Saturated 5(4 H )-oxazolones are easily obtained from N-acylamino acids, and they have been used in coupling reactions as synthetic equivalents of α-amino acids in the synthesis of peptides.…”

Section: Introductionmentioning

confidence: 99%

Ortho-Palladation of (Z)-2-Aryl-4-Arylidene-5(4H)-Oxazolones. Structure and Functionalization

Roiban

Serrano

Soler³

et al. 2010

Organometallics

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Ortho-palladated complexes of (Z)-2-aryl-4-arylidene-5(4H)-oxazolones have been prepared through oxidative addition. The reaction of (Z)-2-phenyl-4-(2-bromobenzylidene)-5(4H)-oxazolone (4) with Pd 2 (dba) 3 3 CHCl 3 gives the six-membered cyclopalladated dinuclear complex [Pd(μ-Br)-(o-C 6 H 4 CHdCNC(O)OCPh)] 2 (7). The reaction of 7 with PPh 3 gives dinuclear 9, which incorporates one phosphine per Pd atom through cleavage of the Pd-N bond, and preserves the bromide bridging system. However, reaction with PPh 2 Me gives mononuclear 8, which incorporates two phosphines as a results of the cleavage of the μ-Br system and N displacement. In contrast, the reaction of 7 with pyridine gives complex 12 due to simple cleavage of the Br bridge, leaving the N-bonding intact. Therefore, three different reaction pathways have been characterized. The reactivity of the Pd-C bond in 7 has also been examined, and functionalized oxazolones can be obtained. The reaction of 7 with PhI(OAc) 2 in acetic acid gives the starting oxazolone C 6 H 4 -2-Br-CHdCNC(O)OCPh ( 4), through the presumed oxidation of the Pd center and C-Br bond formation by reductive coupling. In contrast, the reaction of the acetate dimer 14 with PhI(OAc) 2 in acetic acid gives C 6 H 4 -2-OAc-CHdCNC(O)OCPh (20) through C-O coupling. When treatment of 7 with PhI(OAc) 2 is performed in MeOH or EtOH, the oxazolones C 6 H 4 -2-OR-CHdCNC(O)OCPh (R = Me (18), Et (19)) are obtained. The reaction of 7 with CO in alcohols ROH gives cleanly the oxazolones C 6 H 4 -2-CO 2 R-CHdCNC(O)OCPh (R = Me (21), i Pr (22)) through CO migratory insertion into the Pd-C bond and further nucleophilic attack of the ROfragment.

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“…The absorption spectra in the UV–visible region were measured on a Thermo Scientific Evolution 600 UV–vis spectrophotometer using quartz SUPRAXIL cuvettes, light path 10 mm. The oxazolones 1a–1o used as starting materials were synthesized according to published methods. − …”

Section: Methodsmentioning

confidence: 99%

Reactivity of (Z)-4-Aryliden-5(4H)-thiazolones: [2 + 2]-Photocycloaddition, Ring-Opening Reactions, and Influence of the Lewis Acid BF₃

et al. 2021

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The irradiation of ( Z )-2-phenyl-4-aryliden-5(4 H )-thiazolones 2 with blue light (465 nm) in CH 2 Cl 2 solution promotes [2 + 2]-photocycloaddition of the exocyclic C=C bonds and the formation of the dispirocyclobutanes 3 . This reaction takes place with high stereoselectivity, given that the ε-isomer (1,3 head-to-tail syn coupling) is formed in more than 90% yield in most of the cases. However, irradiation of 5(4 H )-thiazolones 2 with blue light (456 nm) in dry MeOH in the presence of BF 3 ·OEt 2 leads to the monospirocyclobutanes 4 with full stereoselectivity, also affording the ε-isomer. A ring-opening reaction of only one of the thiazolone rings appears to have taken place in 4 upon methanolysis, leading to the corresponding ester and thioamide groups. The treatment of free 4-aryliden-5(4 H )-thiazolones 2 with a base in alcohol (NaOR/ROH) also produces a ring-opening reaction of the heterocycle by methanolysis, although, under these reaction conditions, further intramolecular S-attack at the exocyclic C(H)=C bond and cyclization is observed, forming the dihydrothiazoles 5 or 6 as mixtures of cis ( RS / SR )- and trans ( RR / SS )-isomers with high diastereomeric excess. trans -( RR/SS )-Dihydrothiazoles 6 can be isolated as pure diastereoisomers by column chromatography. Surprisingly, dihydrothiazoles 5 can also be obtained by the treatment of 4-aryliden-5(4 H )-thiazolones 2 with BF 3 ·OEt 2 in methanol in the absence of a base.

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Oxazolones

Cited by 26 publications

References 542 publications

Fluorescence Amplification of Unsaturated Oxazolones Using Palladium: Photophysical and Computational Studies

Fluorescence Amplification of Unsaturated Oxazolones Using Palladium: Photophysical and Computational Studies

Ortho-Palladation of (Z)-2-Aryl-4-Arylidene-5(4H)-Oxazolones. Structure and Functionalization

Reactivity of (Z)-4-Aryliden-5(4H)-thiazolones: [2 + 2]-Photocycloaddition, Ring-Opening Reactions, and Influence of the Lewis Acid BF₃

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Oxazolones

Cited by 26 publications

References 542 publications

Fluorescence Amplification of Unsaturated Oxazolones Using Palladium: Photophysical and Computational Studies

Fluorescence Amplification of Unsaturated Oxazolones Using Palladium: Photophysical and Computational Studies

Ortho-Palladation of (Z)-2-Aryl-4-Arylidene-5(4H)-Oxazolones. Structure and Functionalization

Reactivity of (Z)-4-Aryliden-5(4H)-thiazolones: [2 + 2]-Photocycloaddition, Ring-Opening Reactions, and Influence of the Lewis Acid BF3

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Reactivity of (Z)-4-Aryliden-5(4H)-thiazolones: [2 + 2]-Photocycloaddition, Ring-Opening Reactions, and Influence of the Lewis Acid BF₃