4- 3- - 2-quinoxalinyl

Quinoxalinyl, 4-cinnolinyl, and 1-phthalazinyl derivatives, which are all activated by a combination of induction and resonance, have very similar kinetic characteristics (Table XV, p. 352) in ethoxylation and piperidination, but 2-chloroquinoxaline is stated (no data) to be more slowly phenoxylated. In nucleophilic substitution of methoxy groups with ethoxy or isopropoxy groups, the quinoxaline compound is less reactive than the cinnoline and phthalazine derivatives and more reactive than the quinoline and isoquinoline analogs. 2-Chloroquinoxaline is more reactive than its monocyclic analog, 2-chloropyrazine, with thiourea or with piperidine (Scheme VI, p. 350). 

Depending on the reaction temperature and reaction time, tetrahydroisoquinoline 357 afforded different mixtures of 1,2,3,4,11,11 a-hcxahydro-6//-pyrazino[ 1,2-3]isoquinolines 358-361 and tetracyclic compound 362 (Scheme 30) <2005JA16796>. Each of the individual diastereoisomers 358-361 could be transformed into the compound 362. z7r-3//,4a//-3-Phcnylpcrhydropyra/ino[ 1,2-7]isoquinoline-l,4-dione was prepared via automated parallel solid-phase synthesis on Kaiser oxime resin <1998BML2369>. l,2,3,5,6,7-Hexahydropyrido[l,2,3-r/f ]quinoxaline-2,5-dionc was obtained by catalytic hydrogenation of ethyl 3-(2-oxo-l,2,3,4-tetrahydro-5-quinoxalinyl)acrylate in the presence of TsOH over 5% Pd/C catalyst under 40 psi of hydrogen <1996JME4654>. 

Thermolysis of 3-alkyloxy- and 3-aroyloxy-5-phenyl-l,2,4-pyrrolo[l,2- ]quinoxaline-l,2,4-triones afforded 5-phenyl-9-(4-phenyl-3-oxo-3,4-dihydro-2-quinoxalinyl)-6,8,10-trioxo-5,6,9,10-tetrahydro-87/-pyrido[l,2-tf ]quinoxaline-7,9-dicarboxylates <2000CHE615, 2004CHE1295> and 7-aroyl-8-aroyloxy-5-phenyl-9-(4-phenyl-3-oxo-3,4-dihydro-2-quinoxalinyl)-5,6-dihydro-1077-pyrido[l,2- ]quinoxaline-6,10-diones <2002CHE498>, respectively. Thermolysis of 3-aryl-2-(5-aryl-2,3-dioxo-2,3-dioxo-4-furanyl)quinoxalines gave 7-aroyl-8-aroyloxy-6-aryl-9-(3-aryl-2-quinoxalyl)-10/7-pyrido[l,2- ]quinoxalin-10-ones <2001CHE1314, 2002RCB850>. 

Heteroarylstannanes are more prevalent than their heteroarylboron counterparts. As the following chapters will entail, all of the heteroarylstannanes are known with the one exception of quinoxalinylstannanes at the C(2) and C(3) positions. The exception could be simply a result of lack of necessity — because the same adduct can be obtained simply by using quinoxalinyl halides with other stannanes. 

The reaction of 2-aminoquinoxaline and isopropylidene methoxymethylenemalonate (420) in methanol afforded isopropylidene 2-quinoxalinyl-aminomethylenemalonate (83EUP86723). 

Cyanoquinoxaline reacts with carbanions either at the ring, with displacement of cyanide ion, or at the carbon of the cyano group. Thus acetophenone yields both 2-(2-quinoxalinyl)acetophenone and 3-(2-quinoxalinyl)-3-iminopropiophenone (Ml). 49 Quinoxalinecarbox-anilides 142 undergo intramolecular cyclization to the spiroindoles 143,... 

Reactions of 2-chloro- and 2,3-dichloroquinoxalines with carbanions give 2-quinoxalinyl ketones and 3-chloro-2-quinoxalinyl ketones, respectively e.g., 2-quinoxalinylacetophenone (151) from acetophenone anion.161 However, 2,3-dimethoxy- and 2,3-diethoxy-quinoxaline with methyl ethyl ketone and sodamide in anhydrous benzene give 2-amino derivatives rather than ketones.162... 

Some reactions of 2-methylsulfonylquinoxaline (169) have recently been investigated by Hayashi and his co-workers.176 Reaction of 169 with ketones in benzene in the presence of sodamide yields 2-(2-quinoxalinyl) ketones (see Section IV,F149,161) with active methylene compounds, e.g., ethyl cyanoacetate, the 2-substituted quinoxaline (170) is isolated.176 It was also found that reaction of 2-methylsulfonyl-... 

Hayashi and his co-workers investigated the reactions of 2-substituted quinoxaline 4-oxides with ketones.210-212 2-Phenylquinoxaline 4-oxide (193) yields 2-phenyl-3-phenacylquinoxaline 4-oxide (203) with acetophenone and sodamide. However, 2-cyanoquinoxaline 4-oxide under these conditions yields cu-(3,4-dihydro-3-oxo-2-quinoxalinyl)aceto-phenone (204) by displacement of the cyano group by the ketone carbanion and rearrangement of the N-oxide.212... 

Quinoxaline 1-oxide (209) reacts with phenyl isocyanate to give 2-anilinoquinoxaline (210) together with 1,3-diphenyl-l-(2-quinoxalinyl)-urea (211) and cyclized oxidation product of the urea 212.215 2-Quinoxalinone 4-oxide (205) and its 1-methyl derivative undergo addition reactions, e.g., with phenyl isocyanate and benzyne to give compounds 214 and 216, respectively.216 These reactions are formulated as proceeding via the intermediate cycloadducts 213 and 215. Compound 216 has also been obtained by photolysis of 3-(o-hydroxy-phenyl)quinoxaline 1-oxide.51 1,3-Dipolar cycloaddition of quinoxaline... 

Deshpande, A. M. Natu, A. A. Argade, N. P. Chemo- and regioselective nucleophilic reactions of (brorriorrietliyl) methylrrialeic anhydride synthesis of a-quinoxalinyl- and a-ben-zothiazinylacrylic adds. Heterocydes 1999, 52, 2159-2162. 

The furo[2,3-b]quinoxalines 20 are formed only in cases where the keto group in the intermediate quinoxalinyl ketone 19 is enolizable. If enolization is not possible, the reaction is completed by the formation of product 19 (Scheme 15) (72YZ736). Therefore, it is not surprising that / -dicarbonyl compounds, which are considerably enolized, undergo a very smooth cyclization with tetrachloropyrazine with ethyl acetoacetate, furo [2,3-b] pyrazine is obtained in good yield (Scheme 15) (83JHC365). 

An alternative to qdt, (.S )-2-(3-mercaptoquinoxalinyl)thiourinium, is stable and soluble in aqueous ethanol solutions unlike qdt (27). At pH 10 in ammonia-ammonium chloride buffer, this reagent hydrolyzes to qdt. (5)-2-(3-Mercapto-quinoxalinyl)thiourinium has been used for the simultaneous detection of nickel and cobalt and the determination of palladium (27, 28). A related reagent, 6-nitro-(S)-2-(3-mercaptoquinoxalinyl)thiourinium has also been used in metal analysis (7). This reagent is hydrolyzed in ammonia buffer to generate 6-nitro-2,3-quinoxalinedithiol (nqdt). Following adjustment to pH 2.0, the mixture is extracted with methyl isobutyl ketone and spectrophotometrically analyzed. 6-Nitro-(5)-2-(3-mercaptoquinoxalinyl)thiourinium has been used for the simultaneous spectrophotometric determination of nickel and cobalt by the quantification of [Ni(nqdt)2]2 (710 nm, e = 20,700 L mol 1cm 1) and [Co(nqdt)2]2 (530 nm, e = 40,000 L moE cm-1), respectively. 

Peptidelike macrocyclic antibiotics of dimeric and trimeric form are often found, an example being echinomycin A (quinomycin A) produced by Streptomyces echinatus from the soil of Cuanza (Angola). The complete structure of a large peptide macrocycle bearing two 2-quinoxalinyl substituents has been elucidated by Prelog and co-workers.183... 

Aryl-2-quinoxalinyl(aroyl)ketenes 351, generated in the thermolysis of 3-aroyl-2-(2-aryl-... 

QUINOXALINE 2-p-AMINOBENZENESULPHO-NAMIDOQUINOXALINE n3-2-QUINOXALINYL-SULFANILAMIDE N -2-QUINOXAL LSULFANIL-AMIDE SULFABENZPYRAZINE 2-SULFANIl AMIDOQUINOXALINE SULFAQUINOXALINE... 

Quizalofop or 2-[4-[(6-chloro-2-quinoxalinyl)oxyphenoxy] propanoic acid Aryloxyphenoxy acid Inhibition of fatty acid synthesis selective for grass weeds Potatoes, soy beans, cotton, flax 11-5... 

Reaction of 1-phenylcyclobutene-l,2-dione with benzene-1,2-diamine leads to a quinoxalinyl ketone derivative. 

Quinoxalinyl ketones ean be prepared by condensation of a benzene-1,2-diamine with an appropriate tricarbonyl compound yielding compounds 29. Many syntheses of quinoxaline-2-carbo.xylic acids and their derivatives arc based on the reaction of henzene-1,2-diamine with suitable tricarbonyl compounds. The formation of isomeric mixtures can prove problematic when unsymmetrical diamines arc used in this synthetic approach. 

Quinoxalinyl-a-oxoacetates are prepared with an acyl anion equivalent. 

When 2-chloroquinoxaliiie is treated with a sodium phenolate (see Section 6.3.2.1.4.5.) in an excess of the corresponding phenol, a mixture of the quinoxalinyl ether and the corresponding benzofuro[2,3- ]quinoxaline is obtained. Quinoxalinyl ethers may be cyclized to benzofuro[2,3-b]quinoxaline using polyphosphoric acid. ... 

---