2- Benzoylquinoxalines

Benzoylquinoxaline from its 1,4-dioxide (253, R = H) (substrate, HCl, MeOH, warm then Na2S204-H20 dropwise, until color persisted 74%) also ethyl 3-benzoyl-2-quinoxalinecarboxylate from its 1,4-dioxide (253, R = C02Et)... 

Benzoylquinoxaline (70) gave 2-phenylquinoxaline (71) (Me2SO, NaOH-H20, 60°C, 30 min 34% after separation from several other products) 594 2-p-chlorophenylquinoxaline (67%) and other analogs were made similarly, and a possible mechanism was suggested.594... 

Quinoxalines bearing or//io-metalation directing 2-substituents react with lithium 2,2,6,6-tetramethylpiperidide (LTMP) to produce 2-substituted 3-lithioquinoxalines, which subsequently react with 7V-methoxy-7V-methylbenzamide to give 3-substituted 2-benzoylquinoxalines 20. ... 

A photocyclisation related to that well established for dienones has been reported in the 2-benzoylquinoxaline (39) and yields the purple-coloured methylindoloquinoxallne (40). Synthetically useful benzophenone derivatives (41) have been prepared by photo-Fries rearrangement of the anthranilates (42), and a detailed study of the same photorearrangement in W-acetyl-carbazole has been described. ... 

The IR spectrum of 2-acetyl-3-methylquinoxaline shows carbonyl stretching absorption at 1695 cm in Nujol and therefore in the region to be expected of an aryl methyl ketone. A range of standard derivatives have been prepared from quinoxalinyl ketones (see Table 1) but cycliza-tion occurs on treatment of various 2-benzoylquinoxalines (10) with... 

Although the reaction of 2-benzoylquinoxaline (15) with excess phenylhydrazine gives l,3-diphenylpyrazolo[3,4-h]quinoxaline (18) in 89% yield, reaction with only one equivalent of phenylhydrazine yields only 38% of the diphenylpyrazolo compound. Excess phenylhydrazine also converts the substituted compounds 16 into diphenyl compound 18 in greater than 90% yield. The benzyl and benzoyl analogues 17 give the same product but in lower yield. " ... 

Acetoxymethyl-7-acetyl-2-quinoxalinecarboxamide 1-oxide 2-Acetoxymethyl-3-benzoylquinoxaline 4-oxide 2-Acetoxymethyl-5-methoxy-3-methylquinoxaline 2-Acetoxymethyl-5-methoxy-3-methylquinoxaline 1,4-dioxide 2-Acetoxymethyl-3-methylquinoxaline... 

The 1,5-benzodiazepine 40 on irradiation in benzene under oxygen undergoes oxidative ring contraction to 2-benzoyl-3-methyl-quinoxaline.42 Similarly, photolysis of 7-chloro-2-methylamino-5-phenyl-3//-l,4-benzodiazepine-4-oxide (41) in benzene yields the N-benzoylquinoxaline 42. Related ring contractions of diazepines to reduced quinoxalines have also been observed.43... 

A two-step synthesis of the quinoxalinecarboxamide 11 results from reaction of the dioxobutyrolactone 9 with o-phenylenediamine followed by ring opening of the product (10) with ammonia/ Successive treatment of the lactone 10 with dilute sodium hydroxide and potassium permanganate yields 3-benzoylquinoxaline-2-carboxylic acid/ ... 

Phenyl-3-benzoylquinoxaline 1,4-dioxide dissolved in warm ethanol, and UV-irradiated 3 hrs. with a 450 w. Hanovia Hg-lamp 1,3-dibenzoylbenzimidazolone. Y 50-70%. A.A.Jarrar, J. Chem. Educ. 57, 755 (1974) Heterocycles 4, 1077 (1976). 

The reaction of heterocyclic ketone 34a with benzylamine on heating in DMSO alfords imidazoquinoxaline 12a in quantitative yield. This result is yet another evidence that the formation of imidazoquinoxaline 12a in the reaction of 3-(a-chlorobenzyl)quinoxalin-2(lfl)-one 8 with benzylamine in DMSO also occurs through amine 11 and intermediate imine A (see Scheme 4.5) (Mamedov et al. 2004). 3-Benzoylquinoxalin-2(lfl)-one 34a readily forms upon thermolysis of azide 9 in boiling acetic acid (Scheme 4.16) (Mamedov et al. 2002a). 

Analogously, A-alkylated derivatives 34c-h and 3-acetylquinoxalin-2-one 34b [instead of 3-benzoylquinoxalin-2-one 34a] react with 3-aminomethylpyridine (P-picolylamine) (instead of benzylamine) to give imidazo[l,5-a]quinoxalin-4-ones 35a-l (Scheme 4.17) (Kalinin and Mamedov 2008a Mamedov et al. 2009 Kalinin et al. 2013). 

In addition, compounds containing two benzoylquinoxaline moieties were introduced into this reaction. This enabled the synthesis of bis(imidazoquinoxaline)s in which the quinoxaline moieties are linked with each other through various spacers. In particular, the reaction of a,co-bis(3-benzoylquinoxalin-2-on-l-yl) derivatives 36 with benzyl- and picolylamines on heating in DMSO yields a,to-bis(l,3-diphenyl-and l-pyridyl-3-phenyl-imidazo[l,5-a]quinoxaIin-4-on-5-yl) derivatives 37a-g... 

It reacts with 3-benzoylquinoxalin-2-ones 34a, c-e, i to give l,3-bis(imidazo [l,5-a]quinoxalin-4-on-l-yl)benzenes 39a, c-e, i (Mamedov et al. 2004, 2009 Kalinin and Mamedov 2008b). These compounds are of interest as bidentate chelating agents and precursors of macrocycles (Scheme 4.19). 

It should be noted that the examples of E-type formation of bonds in imidazo[l,5-a] quinoxalines are limited to variant EIq. The three-component reaction of 3-benzoylquinoxalin-2(l//)-one 34a with aromatic aldehydes and NHjOAc in boiling methanol is the only example of Eg-lype synthesis of the imidazo[l,5-a] quinoxaline system (Mamedov et al. 2011). This reaction leads not only to imidazo [l,5-fl]quinoxaline derivatives 12a and 67a-g but also to 2,4,5-trisubstituted imidazoles 68a-h, sometimes as major products. It should be noted that the reaction of A-alkylated 3-benzoylquinoxalin-2(lfl)-one 34i yields only imidazo[l,5-a] quinoxaline 67g. As distinct from variant CIq of synthesis of imidazo[l,5-a] quinoxalines where aminomethyl derivatives are used to introduce the C(l)-N(2) fragment into 3-benzoylquinoxalin-2(lfl)-one, in this case the reaction involves... 

Table 4.2 Three-component reaction of 3-benzoylquinoxalin-2(l//)-one with aromatic aldehydes and NH4OAC for the synthesis of imidazo[l,5-n]quinoxaline system...

The imidazoannulation of 3-benzoylquinoxalin-2-ones has been widely studied on various ketones of quinoxalines in their reactions with compounds containing an aminomethyl moiety (benzylamine picolylamine, m-xylylenediamine), that allowed the creation a library of imidazo[l,5-a]quinoxalines with substituents at different positions (Mamedov et al. 2004a, 2009b, 2008a, b Kalinin et al. 2013). 

Kalinin AA, Mamedov VA (2008b) Polyfused nitrogen heterocycles XIX. Oxidative imidazo-fusion of 3-benzoylquinoxalin-2-ones with benzylamines in the synthesis of bis (imidazo[l,5-a]quinoxalin-l- and -5-yl) derivatives. Russ J Org Chem 44(5) 736-740. doi 10. 1134/S1070428008050187... 

Mamedov VA, Kalinin AA, Gubaidullin AT, Litvinov lA, Levin YA (2003b) 3-Benzoylquinoxalin-2(lfl)-one in the Kostanecki-Robinson reaction. Synthesis and structure of 2-oxo-4-phenylpyrano[2,3-i)]quinoxaline. Chem Heterocyel Compd 39(1) 96-100. doi 10. 1023/A 1023028927007... 

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