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

Abstract

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.

Matrix-isolation FTIR study of azidoacetone and azidoacetonitrile

“…Organic azides are useful reagents in many fields [1][2][3]. Their strongly exothermic reactions make them useful as propellants [4].…”

A new thermal study of the reaction of 6‐azidopyridones with different amines and hydrazines

“…Owing to the importance of this class of heterocycle and also as part of our research program dealing with the synthesis of pharmacologically interesting new heterocycles, particulary those containing the pyridine moiety [15][16][17][18][19], herein we describe the first study on the reaction of 6-azidopyridones 1 [15] with aromatic and aliphatic amines and hydrazines in order to synthesize novel polyfunctionally substituted pyridines of expected significant biological activity, which are often difficult to obtain by alternative routes. Although a number of studies in the chemistry of azide compounds have been carried out [20][21][22][23], to the best of our knowledge, the title studies have not been reported so far.…”

Diels‐alder reaction of 1‐methyl‐3,6,8‐trinitro‐2‐quinolone

“…From the viewpoint of biological and pharmacological interests, syntheses of unnatural compounds possessing the MeQone skeleton are also important projects [6][7][8][9][10], however, direct functionalization of MeQone is not always easy because of its low reactivity. Recently, Fujita and coworkers reported the Diels-Alder reactions of quinolone derivatives having an electron-withdrawing group at the 3-or 4-positions [11][12][13].…”