2-methyl quinoxaline

Treatment of quinoxaline-2-thione (85) with methyl iodide and alkali gives 2-methylthioquinoxaline (86) and apparently no 1-methyl-quinoxaline-2-thione (87). The latter compound is prepared conven-... 

Treatment of bis-lactim ether 420 with BuLi, then with cw-l,4-dichloro-2-butene in the presence of Nal afforded 3,4,9,9n-tetrahydro-6//-pyrido[l,2-fl]pyrazin-4-one (421) with 96% diastereomeric excess (97TA1855). Reaction of l,2-diphenyl-6-methyl-quinoxaline with 1,4-dichlorobutane in THF in the presence of Na at —78°C afforded a 3 1 mixture of 4a,5-diphenyl-9-methyl-l,2,3,4-tetrahydro-4a//-pyrido[l,2-n]quinoxaline and 4-(4-chlorobutyl)-2,3-diphenyl-6-methyl-1,4-dihydroquinoxaline (98JHC1349). 

Bis[(4,4 -bipyridinio)methyl]quinoxaline dibromide (120) gave 2,3-dimethyl quinoxaline (121) (Na2S204, H2O, briefly 93%). °... 

C Nuclear Magnetic Resonance Spectra. The sohd-state CNMR spectra of 6,7-dimethyl-2,3-di(pyridin-2-yl)quinoxahne (130) and its salts have been used to complement X-ray information (see above) on fine structure. A study of the spectra of mono- to tetramethylquinoxalines has made possible the analysis of mixtures of such methylated quinoxalines obtained from ambiguous primary syntheses. 

Nitroquinoxaline (49) with appropriate carbanions gave 2-(dicyanomethyl)-quinoxaline (48) (95%), 2-[di(ethoxycarbonyl)methyl]quinoxaline (50) (85%), and the like. ... 

Methyl-2-quinoxalinamine gave 2-dimethylaminomethyleneamino-3 -methyl-quinoxaline (146) [Me2NCH(OMe)2, PhMe, reflux, 2 h 89%]. ... 

Cyanoamino-3-methylquinoxaline (154) gave 2-(A( -butylguanidino)-3-methyl-quinoxaline (154a) (neat BuNH2, 75°C, 18 h 16%). ... 

Quinoxalinecarbaldehyde 1,4-dioxide (178) gave its acetal, 2-(diethoxy-methyl)quinoxaline 1,4-dioxide (179) (HCl gas/EtOH, reflux, 1 h 47%) and thence the corresponding hydrate 2-(dihydroxymethyl)qumoxalme... 

Phenylimino)methyl]quinoxalme (186) with dimethyl phosphonate gave 2-[a-amlmo-a-(dimethoxyphosphinyl)methyl]quinoxalme (187) (MeONa, MeOH, reflux, several hours >95%) or with diphenylphosphine oxide gave 2-[a-anilino-a-(diphenylphosphinyl)methyl)quinoxaline (188) (MeONa, EtOH, 0°C, 20 min 95%) several analogs likewise. 

Methyl-2( 1 //)-quinoxalinethione (23) gave 2-(2-hydroxyethylamino)-3-methyl-quinoxaline (24) (H2NCH2CH2OH, EtOH, reflux, 2 h 15%).103... 

Chan and coworkers developed a new diphosphine 9, related to MeO-BiPhep 5 (Fig. 10) [21]. [lr(p-Cl)(COD)]2/9/l2 catalytic system provided similar enantios-electivities than [lr(p-Cl)(COD)]2/5/l2 in the Ir-catalyzed hydrogenation of quinolines but higher enantioselectivitites in the reduction of 2-methyl-quinoxaline and 2,3,3-trimethylindolenine (Fig. 10). 

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