Synthesis of 5<i>H</i>-Quinolin[3,4-<i>b</i>][1,4]benzothiazin-6(12H)-ones

Anireddy, Jaya Shree; Rao, V. S.; Darbarwar, M.

doi:10.1080/00397919008052792

Cited by 9 publications

(1 citation statement)

References 4 publications

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“…The 4,11-dimethylbenzopyrano[3,4-b]benzothiazin-2-one 8 was prepared as shown in ( scheme 2) .Thequadricyclic system was synthesized according to the method of Tabakovic [17,20].The addition of 2-aminothiophenol on the substituted-5-hydroxycoumarin 1 was made in polar aprotic solvent (DMSO). This addition was accompanied by the elimination of one molecule of water and conducted to a non-isolable enaminone intermediate [16].…”

Section: (Scheme 1)mentioning

confidence: 99%

Synthesis of 5-Oxycoumarin and Fused Coumarin Derivatives and Evaluation of Their Antitumor Activity.

Al-Wahaibi¹

2016

IJAR

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Section: (Scheme 1)mentioning

confidence: 99%

Synthesis of 5-Oxycoumarin and Fused Coumarin Derivatives and Evaluation of Their Antitumor Activity.

Al-Wahaibi¹

2016

IJAR

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ChemInform Abstract: Synthesis of 5H‐Quino(3,4‐b)(1,4)benzothiazin‐6(12H)‐ones.

1990

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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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Synthesis of 5H-Quinolin[3,4-b][1,4]benzothiazin-6(12H)-ones

Cited by 9 publications

References 4 publications

Synthesis of 5-Oxycoumarin and Fused Coumarin Derivatives and Evaluation of Their Antitumor Activity.

Synthesis of 5-Oxycoumarin and Fused Coumarin Derivatives and Evaluation of Their Antitumor Activity.

ChemInform Abstract: Synthesis of 5H‐Quino(3,4‐b)(1,4)benzothiazin‐6(12H)‐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

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