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Stadlbauer, W.; Fiala, Werner; Fischer, Michaela; Hojas, Gerhard

doi:10.1002/(sici)1521-3897(200001)342:1<33::aid-prac33>3.3.co;2-6

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“…The synthetic thermolysis of the azides 1 2 b , c was performed in refluxing 1,2-dichlorobenzene according to the onset temperatures of 154-160 °C obtained from DSC data; after 10 minutes the evolution of nitrogen gas had stopped and the reaction mixture was worked up. The spectral and microanalytical data were in agreement with the structures of 5-phenyl-12H-q u i n o l i n o [ 3 , 4 -b] [ 1 , 4 ] b e n z o t h i a z i n -6 ( 5H)one 7,7-dioxide (1 3 b) and 4,5,6,14-tetrahydrob e n z o [ 9 , 1 0 ] q u i n o l i z i n o [ 3 , 2 -b] [1,4]benzothiazin-8-one 9,9dioxide (1 3 c), a hitherto unknown class of compounds.…”

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confidence: 75%

“…Two typical examples are the attack of the azide nitrogen either to the 2-position of a phenyl ring in ortho-position to the azide forming indoles [3], or by attack of the azide nitrogen to e.g. the oxygen atom of a carbonyl group in ortho-position to the azide forming isoxazoles [4]. Only in a few cases, the formation of six-membered heterocycles is reported [2], e.g.…”

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Thermolytic ring closure reactions of 4‐azido‐3‐phenylsulfanyl‐and 4‐azido‐3‐phenylsulfonyl‐2‐quinolones to 12H‐quinolino‐[3,4‐b][1,4]benzothiazin‐6(5H)‐ones

Täubl

Langhans

Kappe

et al. 2002

Journal of Heterocyclic Chem

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4-Hydroxy-3-phenylsulfanyl-2-quinolones 2 and 4-hydroxy-3-sulfonyl-2-quinolones 7, which are readily accessible from 4-hydroxy-2-quinolones 1 and diphenyldisulfide or thiophenol, can be converted to 4-azido-3-phenylsulfanyl-2-quinolones 10 or 4-azido-3-phenylsulfonyl-2-quinolones 12 via 4-chloro-3-phenylsulfanyl-2-quinolones 5 or 4-chloro-3-phenylsulfonyl-2-quinolones 9, respectively. Thermolysis of the azides 1 0 and 1 2 results in a cyclization reaction to give quinolino [3,4-b] Organic azides with reactive ortho-groups such as aryl-, heteroaryl-or acyl groups are known to decompose on thermolysis or photolysis followed by a cyclization to heterocycles, either via a nitrene or an electrocyclic mechanism [2]. Mainly, this cyclization type leads to five-membered heterocycles. Two typical examples are the attack of the azide nitrogen either to the 2-position of a phenyl ring in ortho-position to the azide forming indoles [3], or by attack of the azide nitrogen to e.g. the oxygen atom of a carbonyl group in ortho-position to the azide forming isoxazoles [4]. Only in a few cases, the formation of six-membered heterocycles is reported [2], e.g. with a benzyl substituent in ortho-position of the azido group; in this way we obtained from 4-azido-3-benzyl-2-quinolones in good yields dibenzo [b,h][1,6]naphthyridin-6-ones [5]. S i m i l a r l y, the phenylsulfanyl group, Ph-S, or their oxidized variants, the phenylsulfoxide group, Ph-SO, and the phenylsulfonyl group, Ph-SO 2 , seemed to be good candidates for such a thermal azide cyclization.Recently a direct sulfenylation of 4-hydroxy-2-quinolones by the action of diphenyl disulfide has been developed in our group [6,7]. This reaction sequence was used, in this contribution, in order to obtain 4-azido-2-quinolones with phenylsulfanyl groups in 3-position as suitable starting materials for the planned thermal cyclization of azides to six-membered heterocycles. The reaction of 4-hydroxy-2-quinolones 1 with diphenyl disulfide was carried out as described in references [6,7] under basic conditions. During the reaction the thiophenolate anion was formed, which was oxidized by oxygen back to diphenyl disulfide. In contrast to the earlier described method [7], we obtained better results when the air for oxidation was not bubbled through the reaction mixture, but compressed air was blown onto the mixture with a tube ending above the surface of the reaction mixture. This was because the inlet pipe often was clogged when air was bubbled through the mixture. In this way the amount of employed diphenyl disulfide could be reduced to a halfmolar amount and the 3-phenylsulfanyl-2-quinolones 2a-c were obtained in good to excellent yields. There is also the possibility to obtain the thioethers 2 from thiophenol and 3-chloro-4-hydroxyquinolones 4 in pyridine as basic solvent in excellent yields, however this method needs two more steps.

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confidence: 75%

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confidence: 99%

Thermolytic ring closure reactions of 4‐azido‐3‐phenylsulfanyl‐and 4‐azido‐3‐phenylsulfonyl‐2‐quinolones to 12H‐quinolino‐[3,4‐b][1,4]benzothiazin‐6(5H)‐ones

Täubl

Langhans

Kappe

et al. 2002

Journal of Heterocyclic Chem

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“…The literature reports a short number of synthetic routes for 2-arylpyrazolo [4,3-c]coumarins (2-arlychromeno [4,3c]pyrazol-4(2H)-ones), such as cyclization of the 3-hydrazone-4-chloro or 4-hydroxy coumarins, which were relatively unstable and give a mixture of isomeric 1-aryl and 2arylpyrazolo [4,3-c]coumarins [15,16]. These compounds were studied for binding studies interaction with the central benzodiazepine receptor [17].…”

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confidence: 99%

A novel and efficient approach for the synthesis of new halo substituted 2-arylpyrazolo[4,3-c] coumarin derivatives

2011

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“…The direct acetylation of 4-hydroxycoumarin 2 with acetyl chloride 3 using pyridine or piperidine as a catalyst gave 3-acetyl-4-hydroxycoumarin 1 (Stadlbauer and Hojas, 2004;Klosa, 1956) (Scheme 1).…”

Section: Using 4-hydroxycoumarinmentioning

confidence: 99%

“…The condensation reaction of arylhydrazine hydrochlorides or arylhydrazines 36 with 1 either in refluxing acetic acid (Stadlbauer and Hojas, 2004) or ethanol (Catarzi et al, 1995;Colotta et al, 1988) furnished the corresponding hydrazones 37 (Scheme 22).…”

Section: Synthesis Of Hydrazonesmentioning

confidence: 99%

3-Acetyl-4-hydroxycoumarin: Synthesis, reactions and applications

Abdou

2017

Arabian Journal of Chemistry

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The chemistry of 3-acetyl-4-hydroxycoumarin has gained increased interest in both synthetic organic and biological fields, since a large number of developments in the use of such compound seem to be of considerable value. This review summarizes results from the literature concerning the synthesis and reactions of 3-acetyl-4-hydroxycoumarin as well as its applications are also discussed.ª 2014 Production and hosting by Elsevier B.V. on behalf of King Saud University.

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Cited by 5 publications

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Thermolytic ring closure reactions of 4‐azido‐3‐phenylsulfanyl‐and 4‐azido‐3‐phenylsulfonyl‐2‐quinolones to 12H‐quinolino‐[3,4‐b][1,4]benzothiazin‐6(5H)‐ones

Thermolytic ring closure reactions of 4‐azido‐3‐phenylsulfanyl‐and 4‐azido‐3‐phenylsulfonyl‐2‐quinolones to 12H‐quinolino‐[3,4‐b][1,4]benzothiazin‐6(5H)‐ones

A novel and efficient approach for the synthesis of new halo substituted 2-arylpyrazolo[4,3-c] coumarin derivatives

3-Acetyl-4-hydroxycoumarin: Synthesis, reactions and applications

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