syntheses of quinoxalines have attracted a great deal of attention in view of their potent biological and pharmacological activities including anticonvulsant [ 14 ] , antibacterial , antifungal , antiviral , antitubercular , antileishmanial , antiamoebic , analgesic , antihistaminic , antineoplastic , hypoglycemic , mao - a inhibitor , antiarrhythmic , antiatherosclerotic , antiobese , and other diverse pharmacological activities .
earlier studies revealed that most of compounds derived from 1,2,4-triazoles have been found to be significant anticonvulsant   and tranquillizing agents .  
furthermore , compounds 1a  e in figure 1 which contain triazolo[4,3-a]quinoxaline moiety showed promising anticonvulsant activity .
we describe the synthesis and biological evaluation of novel triazolo[4,3-a]quinoxaline derivatives expected to have anticonvulsant activity starting from 1,2-diaminobenzene and oxalic acid via quinoxaline ring build - up .
2,3-dichloroquinoxaline ( 3 ) was prepared by chlorination of 2,3-dihydroxyquinoxaline ( 2 ) , which in turn was prepared by the condensation of the commercially available 1,2-diaminobenzene with oxalic acid in aqueous hydrochloric acid .
treatment of 3 with hydrazine hydrate yielded the corresponding 3-hydrazino compound , 4 , which was subjected to ring closure to 5 by treatment with triethyl orthoformate .
reaction of 5 with thiourea in absolute ethanol afforded the isothiouronium intermediate which upon basic hydrolysis yielded triazolo[4,3-a]quinoxaline-4-thiol ( 6 ) .
the potassium salt 7 was obtained after treatment of 6 with alcoholic koh in a quantitative yield .
reaction of the potassium salt 7 with substituted aniline in dmf gave the corresponding anilide 8a  d , and its reaction with alkyl chloroacetate in the same solvent gave the corresponding ester 9a  e .
the hydrazide derivative 10 was synthesized from the reaction of n - butyl ester with hydrazine hydrate .
thus , that hydrazide was allowed to react with ethyl acetoacetate and acetylacetone to give the corresponding methylpyrazolone derivative 11 and dimethylpyrazole derivative 12 , respectively . when compound 10 was treated with carbon disulphide and potassium hydroxide ,
allowing the same intermediate 10 to react with isocyanate or with isothiocyanates resulted in the formation of semicarbazide 14 and thiosemicarbazides 15 , respectively .
acetylation of compound 10 with acetic anhydride and condensation with variety of aromatic aldehydes gave the corresponding n - acetyl derivative 16 and n - arylidene derivatives 17a  f , respectively .  
the structural assignments to the new compounds were based on their elemental analysis and spectral ( ir , h  nmr , and mass ) data .
eleven compounds of the newly synthesized derivatives were selected to be screened for their anticonvulsant activity on different groups of mice .
swiss albino adult male mice , weighing 2025  g , were used as experimental animals .
they were obtained from an animal facility ( animal house , department of pharmacology and toxicology , faculty of pharmacy , al - azhar university ) .
animals were kept under well - ventilated conditions at room temperature ( 2530c ) . they were fed on an adequate standard laboratory chow ( el - nasr co. , abou - zabal , egypt ) and allowed to acclimatize with free access to food and water for 24-hour period before testing except during the short time
the tested compounds were dissolved in dmso and orally administered in a dose regimen ranging from 200 to 800  mg / kg animal weight , using the dosing volume of 0.2  ml per 20  g. pentylenetetrazole was dissolved in normal saline in 2% concentration and was given intraperitoneally in a dose of 60  mg / kg body weight ( dose that could induce convulsions in at least 80% of the animals without death during the following 24 hours ) .
phenobarbitone sodium ( alex co. , egypt ) was dissolved in normal saline in 2% concentration and it was intraperitoneally given in doses of 6.25 , 12.5 , and 25  mg / kg using the same dosing volume .
groups of six mice were administered the graded doses of the test compounds and phenobarbitone sodium orally .
control animals received an equal volume of saline ( 10  ml / kg ) .
after one hour , the animals were subcutaneously injected with the convulsive dose of pentylenetetrazole ( 60  mg / kg ) .
doses that gave full protection against the induced convulsions and those which exhibited 50% protection in addition to the relative potencies of the test compounds to phenobarbitone sodium were recorded in table 1 .
the ir spectra ( in kbr discs ) were recorded on potassium bromide discs on a pye unicam sp 3300 spectrophotometer .
h  nmr spectra were recorded either on gemini 300  mhz ( varian usa ) or on jeol eca 500  mhz nmr spectrometer ( 500  mhz ) using tms as an internal standard .
mass spectra were recorded on a shimadzu gcms - qp 1000 ex mass spectrometer operating at 70  ev .
elemental analysis was carried out at the regional center for mycology and biotechnology , al - azhar university , cairo , egypt .
progress of the reactions was monitored by tlc sheets precoated with uv fluorescent silica gel merck 60 f254 plates and was visualized using uv lamp and n - hexane  :  ethyl acetate 9  :  1 as mobile phase .
compounds 26 were prepared following the procedures reported in the literature [ 2224 ] . the used intermediates ( chloroacetanilides and alkyl chloroacetates )
compound 6 ( 1.5  g , 0.01  mol ) was treated with alcoholic solution of potassium hydroxide ( 0.4  g , 0.01  mol ) ; the reaction mixture was stirred for 1  h ; the solid obtained was filtered , washed with absolute ethanol , and air - dried to give the potassium salt in quantitative yield .
ir ( kbr ) cm : 3391 , 3127 , 2833 , 1629 , 1479 , 1412 , 1309 , 1209 , 1065 , 972 . ms ( m / z , % ): 240 ( m , 0.9 ) , 233 ( 4 ) , 202 ( 6 ) , 160 ( 7 ) , 143 ( 42 ) , 118 ( 34 ) , 102 ( 11 ) , 91 ( 22 ) , 77 ( 24 ) , 63 ( 100 ) , 51 ( 27 ) . h  nmr ( dmso - d6 , 300  mhz )  : 7.13 ( t , 1h , j = 7.50  hz ) , 7.27 ( t , 1h , j = 7.50  hz ) , 7.56 ( d , 1h , j = 7.20  hz ) , 8.07 ( d , 1h , j = 7.20  hz ) , 9.77 ( s , 1h , triazolo proton ) .
calcd . for c10h8kn4s : c , 44.98 ; h , 2.10 ; n , 23.31 .
general procedure : a mixture of compound 7 ( 1.0  g , 0.01  mol ) and the appropriate chloroacetanilide ( 0.01  mol ) in dmf ( 20  ml ) was heated over a water bath for 3  h. the reaction mixture was then cooled , poured into ice - cooled water ( 200  ml ) , and stirred well for 30  min .
the solid thus separated was filtered , washed with water , dried , and crystallized from methanol / toluene mixture ( 1  :  1 ) to obtain compounds 8a  d . 

ir ( kbr ) cm : 3216 , 3071 , 1666 , 1599 , 1537 , 1463 , 1318 , 1242 , 1066 , 955 .
ms ( m / z , % ): 335 ( m , 0.1 ) , 243 ( 1 ) , 215 ( 2 ) , 203 ( 11 ) , 143 ( 14 ) , 132 ( 25 ) , 119 ( 22 ) , 104 ( 14 ) , 91 ( 100 ) , 77 ( 44 ) , 64 ( 82 ) , 50 ( 26 ) .
h  nmr ( dmso - d6 , 500  mhz )  : 4.34 ( s , 2h ) , 7.02 ( t , 1h , j = 7.56  hz ) , 7.26 ( t , 2h , j = 7.56  hz ) , 7.58 ( m , 4h ) , 7.85 ( d , 1h , j = 8.40  hz ) , 8.32 ( d , 1h , j = 7.65  hz ) , 10.09 ( s , 1h , triazolo proton ) . anal . calcd . for c17h13n5os
: c , 60.88 ; h , 3.91 ; n , 20.88 . found : c , 61.08 ; h , 3.90 ; n , 20.94% . 

ir ( kbr ) cm : 3522 , 3205 , 3122 , 1681 , 1591 , 1459 , 1364 , 1247 , 1057 , 957 .
h  nmr ( dmso - d6 , 500  mhz )  : 4.32 ( s , 2h ) , 7.10 ( t , 1h , j = 7.65  hz ) , 7.43 ( m , 4h ) , 7.89 ( d , 2h , j = 7.65  hz ) , 8.17 ( t , 1h , j = 7.65  hz ) , 10.09 ( s , 1h , triazolo proton ) .
calcd . for c18h13n5o3s : c , 56.98 ; h , 3.45 ; n , 18.46 . found : c , 57.19 ; h , 3.44 ; n , 18.51% .  

ir ( kbr ) cm : 3675 , 3566 , 3021 , 2855 , 1678 , 1602 , 1521 , 1451 , 1388 , 1285 , 1056 , 959 .
ms ( m / z , % ): 351 ( m , 0.2 ) , 243 ( 8) , 215 ( 7 ) , 202 ( 100 ) , 143 ( 13 ) , 131 ( 5 ) , 109 ( 15 ) , 102 ( 5 ) , 90 ( 13 ) , 77 ( 5 ) , 63 ( 13 ) , 51 ( 21 ) .
: c , 58.11 ; h , 3.73 ; n , 19.93 . found : c , 58.10 ; h , 3.72 ; n , 19.86% . 

ir ( kbr ) cm : 3677 , 3075 , 1695 , 1588 , 1503 , 1464 , 1341 , 1274 , 1066 , 952 .
ms ( m / z , % ): 380 ( m , 0.5 ) , 243 ( 24 ) , 216 ( 80 ) , 202 ( 21 ) , 188 ( 32 ) , 143 ( 28 ) , 134 ( 18 ) , 102 ( 22 ) , 89 ( 100 ) , 76 ( 75 ) , 63 ( 88 ) , 51 ( 97 ) .
: c , 53.68 ; h , 3.18 ; n , 22.09 . found : c , 53.87 ; h , 3.17 ; n , 22.16% .  
general procedure : equimolar quantities of the potassium salt 7 ( 1.2  g , 0.01  mol ) and alkyl chloroacetate ( 0.01  mol ) in dmf ( 20  ml ) were heated on water bath for 3  h. the reaction mixture was poured onto ice water ( 200  ml ) , and stirred for 30  min .
ir ( kbr ) cm : 3454 , 1722 , 1464 , 1316 , 1200 , 1060 , 982 , 952 .
( m / z , % ): 274 ( m , 10 ) , 243 ( 4 ) , 215 ( 100 ) , 188 ( 55 ) , 170 ( 15 ) , 161 ( 26 ) , 143 ( 36 ) , 122 ( 16 ) , 116 ( 13 ) , 102 ( 11 ) , 76 ( 8) , 58 ( 46 ) .
h  nmr ( dmso - d6 , 500  mhz )  : 3.35 ( s , 3h ) , 4.27 ( s , 2h ) , 7.62 ( m , 2h ) , 7.83 ( d , 1h , j = 7.65  hz ) , 8.32 ( d , 1h , j = 8.6  hz ) , 10.09 ( s , 1h , triazolo proton ) .
calcd . for c18h13n5o3s : c , 52.54 ; h , 3.67 ; n , 20.43 .
ir ( kbr ) cm : 3099 , 2966 , 2346 , 1727 , 1641 , 1486 , 1388 , 1171 , 1035 , 951 . ( m / z , % ): 288 ( m , 16 ) , 243 ( 19 ) , 215 ( 100 ) , 188 ( 61 ) , 170 ( 25 ) , 161 ( 39 ) , 143 ( 42 ) , 121 ( 18 ) , 115 ( 18 ) , 102 ( 14 ) , 75 ( 21 ) , 50 ( 10 ) . h  nmr ( cdcl3 , 300  mhz )  : 1.29 ( t , 3h , j = 4.5  hz ) , 4.18 ( q , 2h , j = 3  hz ) , 4.30 ( s , 2h ) , 7.59 ( m , 2h ) , 7.88 ( d , 1h , j = 3.6  hz ) , 7.94 ( d , 1h , j = 3.6  hz ) , 9.28 ( s , 1h , triazolo proton ) .
for c13h12n4o2s : c , 54.15 ; h , 4.20 ; n , 19.43 . found : c , 54.34 ; h , 4.21 ; n , 19.37% .  

ir ( kbr ) cm : 3423 , 3069 , 2966 , 1743 , 1641 , 1390 , 1299 , 1167 , 1063 , 960 .
( m / z , % ): 303 ( m + 1 , 40 ) , 302 ( m , 16 ) , 243 ( 14 ) , 215 ( 100 ) , 188 ( 26 ) , 170 ( 13 ) , 161 ( 9 ) , 143 ( 16 ) , 122 ( 12 ) , 116 ( 8) , 102 ( 7 ) , 90 ( 13 ) , 63 ( 4 ) .
anal . calcd . for c14h14n4o2s : c , 55.61 ; h , 4.67 ; n , 18.53 .
ir ( kbr ) cm : 3446 , 2934 , 2725 , 1728 , 1626 , 1552 , 1468 , 1368 , 1171 , 1063 , 953 .
h  nmr ( cdcl3 , 300  mhz )  : 0.77 ( t , 3h , j = 7.2  hz ) , 1.21 ( sextet , 2h , j = 7.2  hz ) , 1.51 ( p , 2h , j = 6.3  hz ) , 4.09 ( t , 2h , j = 6.3  hz ) , 4.29 ( s , 2h ) , 7.30 ( m , 2h ) , 8.18 ( d , 1h , j = 6  hz ) , 8.35 ( d , 1h , j = 5.4  hz ) , 9.96 ( s , 1h ) . anal . calcd . for c15h16n4o2s : c , 56.94 ; h , 5.10 ; n , 17.71 . found : c , 56.92 ; h , 5.07 ; n , 17.69% . 

ir ( kbr ) cm : 3052 , 2976 , 2926 , 1738 , 1466 , 1306 , 1146 , 1068 , 956 .
( m / z , % ): 316 ( m , 3 ) , 260 ( 11 ) , 243 ( 10 ) , 216 ( 46 ) , 188 ( 23 ) , 143 ( 7 ) , 121 ( 4 ) , 102 ( 3 ) , 90 ( 7 ) , 56 ( 100 ) .
h  nmr ( dmso - d6 , 500  mhz )  : 1.33 ( s , 9h ) , 4.13 ( s , 2h ) , 7.64 ( m , 2h ) , 7.85 ( d , 1h , j = 7.65  hz ) , 8.33 ( d , 1h , j = 7.65  hz ) . anal . calcd . for c15h16n4o2s
: c , 56.94 ; h , 5.10 ; n , 17.71 . found : c , 56.72 ; h , 5.09 ; n , 17.63% .  
compound 9b ( 3.3  g , 0.01  mol ) was dissolved in absolute ethanol ( 50  ml ) and treated with hydrazine hydrate ( 95% , 20  ml ) .
the reaction mixture was stirred well and heated to 50c for two hours , then cooled and treated with water ( 200  ml ) .
the solid thus obtained was filtered , washed with water , dried , and then crystallized from glacial acetic acid to give 2.85  g ( 91% ) , m.p .
> 360c , ir ( kbr ) cm : 3412 , 3196 , 3072 , 1630 , 1488 , 1388 , 1250 , 1164 , 1058 , 954 .
ms ( m / z , % ): 274 ( m , 4 ) , 215 ( 7 ) , 202 ( 22 ) , 169 ( 26.86 ) , 143 ( 16 ) , 128 ( 47 ) , 102 ( 22 ) , 76 ( 100 ) , 51 ( 68 ) .
h  nmr ( dmso - d6 , 500  mhz )  : 4.08 ( s , 2h ) , 7.62 ( m , 2h ) , 7.92 ( d , 1h , j = 7.6  hz ) , 8.31 ( d , 1h , j = 7.6  hz ) , 10.05 ( s , 1h ) . anal . calcd . for c11h10n6os
found : c , 48.03 ; h , 3.68 ; n , 30.74% .   a mixture of 10 ( 1  g , 0.0028  mol ) and acetylacetone ( 0.36  g , 0.0028  mol ) in absolute ethanol ( 20  ml ) was heated at 80c on a water bath for 7  h. the reaction mixture was cooled and poured onto water , and the formed precipitate was filtered and crystallized from ethanol to give 0.78  g ( 64% ) , m.p .
236238c , ir ( kbr ) cm : 3078 , 1721 , 1572 , 1488 , 1321 , 1230 , 1133 , 1031 , 956 .
ms ( m / z , % ): 338 ( m , 0.06 ) , 265 ( 35 ) , 249 ( 4 ) , 237 ( 39 ) , 222 ( 24 ) , 195 ( 11 ) , 169 ( 10 ) , 143 ( 14 ) , 115 ( 11 ) , 102 ( 18 ) , 76 ( 34 ) , 51 ( 100 ) .
h  nmr ( dmso - d6 , 500  mhz )  : 2.21 ( s , 3h ) , 3.26 ( s , 3h ) , 4.26 ( s , 2h ) , 6.23 ( s , 1h , pyrazole proton ) , 7.67 ( t , 1h , j = 7.65  hz ) , 7.77 ( t , 1h , j = 7.65  hz ) , 7.98 ( d , 1h , j = 8.4  hz ) , 8.43 ( d , 1h , j = 7.65  hz ) , 10.17 ( s , 1h , triazolo proton ) . anal . calcd . for c16h14n6os
found : c , 56.99 ; h , 4.15 ; n , 24.91% .   a mixture of 10 ( 1  g , 0.0028  mol ) and ethyl acetoacetate ( 0.47  g , 0.0028  mol ) in dioxane ( 20  ml ) was heated under reflux for 5  h. the reaction mixture was cooled and poured onto water , and the formed precipitate was filtered and then crystallized from dioxane to give 0.37  g ( 30% ) , m.p .
242244c , ir ( kbr ) cm : 3412 , 3192 , 3069 , 1635 , 1491 , 1388 , 1248 , 1180 , 1062 , 970 .
ms ( m / z , % ): 340 ( m , 2 ) , 221 ( 3 ) , 201 ( 2 ) , 135 ( 6 ) , 121 ( 3 ) , 69 ( 48 ) , 55 ( 100 ) .
h  nmr ( dmso - d6 , 300  mhz )  : 3.43 ( s , 3h ) , 4.38 ( s , 2h , s 
ch2 ) , 5.61 ( s , 2h , ch2 of pyrazole ring ) , 7.418.39 ( m , 4h ) , 10.13 ( s , 1h , triazolo proton ) . anal . calcd . for c15h12n6o2s
found : c , 53.14 ; h , 3.56 ; n , 24.72% .   a mixture of 10 ( 1  g , 0.01  mol ) , koh ( 0.01  mol ) , and cs2 ( 20  ml ) in dmf ( 20  ml ) was heated under reflux until the h2s ceased to evolve ( about 5  h ) .
the excess solvent was removed by distillation , the residue was stirred with water and filtered , and the filtrate was acidified with 10% hcl .
the precipitated solid was filtered , washed with water , and crystallized from ethanol to give 0.9  g ( 86% ) , m.p .
> 360c , ir ( kbr ) cm : 3428 , 3111 , 2896 , 1642 , 1467 , 1396 , 1257 , 1098 , 952 .
ms ( m / z , % ): 316 ( m , 6 ) , 242 ( 10 ) , 215 ( 6 ) , 210 ( 21 ) , 202 ( 81 ) , 143 ( 11 ) , 121 ( 7 ) , 105 ( 17 ) , 77 ( 18 ) , 52 ( 100 ) .
h  nmr ( dmso - d6 , 500  mhz )  : 4.79 ( s , 2h ) , 7.59 ( m , 2h ) , 8.28 ( d , 1h , j = 7.65  hz ) , 9.91 ( d , 1h , j = 7.56  hz ) , 10.10 ( s , 1h , triazolo proton ) . anal .
calcd . for c12h8n6os2 : c , 45.56 ; h , 2.55 ; n , 26.56 .
compound 10 ( 1  g , 0.006  mol ) and cyclohexyl isocyanate ( 0.45  g , 0.006  mol ) in benzene were heated under reflux for 24  h. after cooling , the precipitate was collected and crystallized from ethanol to give 1.1  g ( 80% ) , m.p .
> 360c , ir ( kbr ) cm : 3390 , 3091 , 2929 , 1669 , 1534 , 1497 , 1334 , 1239 , 1175 , 954 .
h  nmr ( dmso - d6 , 500  mhz )  : 0.971.78 ( m , 11h ) , 4.15 ( s , 2h ) , 7.087.29 ( m , 4h ) , 9.57 ( s , 1h , triazolo proton ) .
: c , 54.12 ; h , 5.30 ; n , 24.54 . found : c , 54.31 ; h , 5.30 ; n , 24.61% .   a mixture of compound 10 ( 1  g , 0.006  mol ) and the appropriate thiocyanate ( 0.006  mol ) in 20  ml absolute ethanol was heated under reflux for 3  h. after cooling ,
the precipitate was collected and crystallized from dioxane to obtain compounds ( 15a - b ) .  

238240c , ir ( kbr ) cm : 3495 , 3066 , 1701 , 1639 , 1522 , 1316 , 1227 , 1051 , 955 .
ms ( m / z , % ): 361 ( m+1 , 8) , 241 ( 9 ) , 211 ( 9 ) , 201 ( 8.36 ) , 184 ( 31 ) , 157 ( 25 ) , 122 ( 9 ) , 115 ( 14 ) , 102 ( 15 ) , 77 ( 13 ) , 63 ( 100 ) . h  nmr ( dmso - d6 , 300  mhz )  : 0.99 ( t , 3h , j = 6.9  hz ) , 1.06 ( q , 2h , j = 6.9  hz ) , 4.29 ( s , 2h ) , 7.67 ( m , 2h ) , 7.96 ( d , 1h , j = 7.2  hz ) , 8.35 ( d , 1h , j = 7.5  hz ) , 10.11 ( s , 1h , triazolo proton ) .
calcd . for c14h15n7os2 : c , 46.52 ; h , 4.18 ; n , 27.13 . found : c , 46.68 ; h , 4.19 ; n , 27.21% .  

300302c , ir ( kbr ) cm : 3499 , 3173 , 2988 , 1701 , 1688 , 1526 , 1329 , 1246 , 1061 , 960 .
h  nmr ( dmso - d6 , 500  mhz )  : 4.21 ( s , 2h ) , 7.627.31 ( m , 4h ) , 7.337.65 ( m , 4h ) , 10.02 ( s , 1h , triazolo proton ) .
: c , 52.80 ; h , 3.69 ; n , 23.94 . found : c , 52.99 ; h , 3.70 ; n , 24.01% . the hydrazide 10 ( 1  g , 2  mmol ) was warmed with acetic anhydride ( 5  ml ) for 1  h , and then the mixture was allowed to attain room temperature .
the deposited red solid was filtered , washed with petroleum ether ( 6080c ) , and crystallized from ethanol to afford 0.5  g ( 45% ) , m.p .
200202c , ir ( kbr ) cm : 3433 , 3130 , 3011 , 1727 , 1670 , 1499 , 1370 , 1238 , 1022 , 976 .
ms ( m / z , % ): 316 ( m , 0.1 ) , 242 ( 36 ) , 200 ( 86 ) , 170 ( 100 ) , 143 ( 89 ) , 116 ( 50 ) , 75 ( 48 ) , 50 ( 34 ) .
h  nmr ( dmso - d6 , 300  mhz )  : 2.40 ( s , 3h ) , 4.20 ( s , 2h ) , 7.69 ( m , 2h ) , 8.04 ( d , 1h , j = 7.8  hz ) , 8.43 ( d , 1h , j = 7.8  hz ) , 10.19 ( s , 1h , triazolo proton ) . anal . calcd . for c13h12sn6o2s : c , 49.36 ; h , 3.82 ; n , 26.57 . found : c , 49.53 ; h , 3.83 ; n , 26.65% .  
general procedure : a mixture of 1.0  g ( 0.028  mol ) of compound 10 and the appropriate aromatic aldehyde ( 0.029  mol ) in absolute ethanol ( 20  ml ) and catalytic amount of glacial acetic acid ( 2  ml ) was refluxed for 3 - 4  h , and the reaction mixture was then poured onto water .
the solid so obtained was filtered and crystallized from acetic acid to obtain compounds 17a  f .  

350352c , ir ( kbr ) cm : 3438 , 3116 , 2925 , 1716 , 1645 , 1480 , 1388 , 1262 , 1169 .
h  nmr ( dmso - d6 , 500  mhz )  : 4.65 ( s , 2h ) , 7.577.63 ( m , 5h ) , 8.07 ( s , 1h ) , 8.098.36 ( m , 4h ) , 9.92 ( s , 1h , triazolo proton ) . anal . calcd . for c18h14n6os
282284c , ir ( kbr ) cm : 3450 , 3097 , 1708 , 1626 , 1478 , 1389 , 1240 , 1045 , 955 .
h  nmr ( dmso - d6 , 300  mhz )  : 1.91 ( s , 3h ) , 5.59 ( s , 2h ) , 7.137.34 ( m , 4h ) , 7.687.89 ( m , 4h ) , 8.54 ( s , 1h ) , 10.13 ( s , 1h , triazolo proton ) .
calcd . for c19h16n6os : c , 60.62 ; h , 4.28 ; n , 22.33 . found : c , 60.88 ; h , 4.29 ; n , 22.40% .  

274276c , ir ( kbr ) cm : 3340 , 3192 , 3054 , 1607 , 1471 , 1378 , 1237 , 1160 , 1062 , 962 .
ms ( m / z , % ): 378 ( m , 7 ) , 302 ( 7 ) , 243 ( 7 ) , 215 ( 10.32 ) , 201 ( 16 ) , 143 ( 19 ) , 120 ( 30 ) , 102 ( 16 ) , 76 ( 28 ) , 51 ( 100 ) .
h  nmr ( dmso - d6 , 500  mhz )  : 4.65 ( s , 2h ) , 6.756.85 ( m , 4h ) , 7.13 ( t , 1h , j = 7.65  hz ) , 7.33 ( t , 1h , j = 7.65  hz ) , 8.01 ( d , 1h , j = 8.4  hz ) , 8.32 ( d , 1h , j = 8.4  hz ) , 8.47 ( s , 1h ) , 10.04 ( s , 1h , triazolo proton ) . anal . calcd . for c18h14n6o2s : c , 57.13 ; h , 3.73 ; n , 22.21 . found : c , 57.35 ; h , 3.72 ; n
288290c , ir ( kbr ) cm : 3435 , 3101 , 3054 , 1622 , 1457 , 1396 , 1266 , 1193 , 1058 , 958 .
h  nmr ( dmso - d6 , 500  mhz )  : 4.29 ( s , 2h ) , 6.836.91 ( m , 4h ) , 7.227.32 ( m , 4h ) , 9.00 ( s , 1h ) , 10.03 ( s , 1h , triazolo proton ) .
calcd . for c18h14n6o2s : c , 57.13 ; h , 3.73 ; n , 22.21 . found : c , 57.10 ; h , 3.69 ; n , 22.15% .  

290292c , ir ( kbr ) cm : 3450 , 3093 , 1629 , 1482 , 1349 , 1226 , 1084 , 955 , ms ( m / z , % ): 396 ( m , 0.04 ) , 398 ( 0.03 ) , 361 ( 0.05 ) , 322 ( 5 ) , 285 ( 0.04 ) , 243 ( 4 ) , 215 ( 6 ) , 201 ( 6.02 ) , 185 ( 100 ) , 143 ( 7 ) , 123 ( 34 ) , 102 ( 57 ) , 76 ( 45 ) , 50 ( 89 ) .
h  nmr ( dmso - d6 , 300  mhz )  : 4.73 ( s , 2h ) , 7.207.39 ( m , 4h ) , 7.487.69 ( m , 4h ) , 8.49 ( s , 1h ) , 9.95 ( s , 1h , triazolo proton ) . anal . calcd . for c18h13cln6os : c , 54.48 ; h , 3.30 ; n , 21.18 . found : c , 54.62 ; h , 3.30 ; n , 21.24%
290292c , ir ( kbr ) cm : 3420 , 3328 , 3106 , 1620 , 1476 , 1371 , 1244 , 1158 , 1025 , 952 .
ms ( m / z , % ): 431 ( m , 0.03 ) , 395 ( 0.04 ) , 321 ( 5 ) , 243 ( 0.6 ) , 215 ( 1 ) , 211 ( 5 ) , 185 ( 100 ) , 143 ( 8) , 123 ( 14 ) , 76 ( 3 ) , 51 ( 6 ) . anal . calcd . for c18h12c12n6os
: c , 50.13 ; h , 2.80 ; n , 19.49 . found : c , 50.31 ; h , 2.79 ; n , 19.43% .
in the present investigation , 16 new 4-substituted triazolo[4,3-a]quinoxaline derivatives were synthesized and characterized by spectral analysis .
the activity may be explained by the presence of substituents on position 4 of the condensed heterocyclic system containing quinoxaline , fused to triazole at 1,2 positions in the backbone structure of title compounds .
the electronic factors exerted by the substituents and the hydrophobic nature of phenyl nucleus in the title compounds influenced the activity .
 2-([1,2,4]triazolo[4,3-a]quinoxalin-4-ylthio)acetic acid hydrazide ( 10 ) was used as a precursor for the syntheses of novel quinoxaline derivatives with potential anticonvulsant properties . 
 the newly synthesized compounds have been characterized by ir , 1h  nmr , and mass spectral data followed by elemental analysis . 
 the anticonvulsant evaluation was carried out for eleven of the synthesized compounds using metrazol induced convulsions model and phenobarbitone sodium as a standard . among 
 this set of tested compounds , two of them ( 14 , and 15b ) showed the best anticonvulsant activities . 
1. Introduction
2. Results and Discussion
3. Biological Activity
4. Experimental
5. Conclusion