the benzo [ c ] furan system , trivially called isobenzofuran , has come to light from 1960s .
there are records for the reactivity of substituted isobenzofurans as dienes in the diels - alder reaction [ 1 , 2 ] .
citalopram ( figure 1 ) , a well - known compound , affects serotonin metabolism in the brain and thus acts as an antidepressant drug .
citalopram is prescribed for treating major depression , social anxiety [ 5 , 6 ] , panic disorder [ 79 ] , diabetic neuropathy , premature ejaculation [ 11 , 12 ] , and poststroke pathological crying [ 13 , 14 ] .
the pharmacological profiles of 3-mercapto-1,2,4-triazoles are tested meticulously for their antimicrobial [ 18 , 19 ] , anticonvulsant , and antidepressant activities .
an attempt to prepare 2-amino-5-substituted-1,3,4-thiadiazoles from substituted acyl thiosemicarbazides 11 has failed to furnish the corresponding products .
the decomposition of the starting material is indicated by h nmr and c nmr spectra .
this reaction in acidic medium is dependent on both ph of the medium and substituents of acylthiosemicarbazides .
the probable reason for the failure may be the steric hindrance posed by bulky isobenzofuran component for cyclization pathway .
this paper portrays the synthetic tactic for the preparation of 3-mercapto-1,2,4-triazole derivatives bearing isobenzofuran moiety and an assessment of their antimicrobial action .
the ir ( kbr ) spectra are recorded on shimadzu 8300 fourier transform infrared spectrometer .
h nmr is recorded on bruker am 400  mhz spectrometer and c nmr is recorded on bruker am 100  mhz spectrometer using dmso as solvent and tms as an internal standard ( chemical shift in ppm ) .
mass spectral ( ms ) analysis is carried out on agilent 6520 esiqtof ms with ionization source esiqtof and acetonitrile as solvent ( 110 volts ) .
thin layer chromatography is conducted on 0.25  mm silica gel plates ( 60f254 , merck ) .
reagents are obtained commercially and used as received . to a cooled solution of sncl2 ( 1.0  g , 5.27  mmol ) in conc .
hcl ( 20  ml ) add 4-nitrophthalimide 1 ( 5.0  g , 0.026  mol ) slowly under stirring .
after complete addition , the reaction mass is stirred for 3  h at r.t .
the reaction mass is cooled and the solid formed is filtered and washed with chilled water .
the wet solid 2 ( 4  g , 0.024  mol ) is dissolved in 30% aq .
zn dust ( 2  g , 0.030  mol ) is added to the mixture and refluxed for 4  h. the residue is filtered and the filtrate is acidified with conc .
this mass is refluxed again for 2  h. thereafter , the reaction mass is cooled and the ph is adjusted to neutral using liq . nh3 .
the solid formed is filtered and recrystallised from boiling methanol to afford 5-amino-3h - isobenzofuran-1-one 3 as off white solid , yielding 3.0  g ( 83% ) , m.p .
186188c ; ir ( kbr pellet , cm ) :  3133 ( nh ) , 3085 ( aromatic ch ) , 1644 ( c = o ) , 1620 , 1471 ( aromatic c = c ) , 1044 ( coc ) , 1022 ( cn ) ; h nmr ( dmso , 400  mhz ) :  7.55 ( d , j = 8.0  hz , 1h , arh ) , 6.626.69 ( m , 2h , arh ) , 5.32 ( s , 2h , ch2 ) , 5.13 ( bs , 2h , nh2 ) ; c nmr ( dmso , 400  mhz ) :  169.0 , 141.7 , 137.6 , 133.0 , 131.9 , 128.9 , 124.4 , 70.5 ; anal .
calcd . for c8h7no2 : c , 64.42 ; h , 4.73 ; n , 9.39 .
found : c , 64.49 ; h , 4.69 ; n , 9.34 . dissolve 5-amino-3h - isobenzofuran-1-one 3 ( 2.00  g , 0.013  mol ) in conc .
dilute with water ( 30  ml ) and stir to make a homogeneous solution .
cool in ice and add nano2 ( 1.10  g , 0.016  mol ) solution in water ( 2.5  ml ) under stirring . to this cool diazonium salt solution add cucn ( 1.42  g , 0.015  mol ) slowly in small quantities with warming on a water bath at 60c .
reflux for 30  min and then cool the reaction mass to get the title compound 4 which is recrystallised from ethyl acetate , yielding 1.68  g ( 84% ) , m.p .
202204c ; ir ( kbr pellet , cm ) :  3043 ( aromatic ch ) , 2251 ( cn ) , 1685 ( c = o ) , 1670 , 1444 ( c = c ) , 1037 ( coc ) ; h nmr ( dmso , 400  mhz ) :  8.01 ( d , j = 7.5  hz , 1h , arh ) , 7.65 ( d , j = 7.5  hz , 1h , arh ) , 7.62 ( s , 1h , arh ) , 5.38 ( s , 2h , ch2 ) ; c nmr ( dmso , 400  mhz ) :  171.1 , 140.6 , 137.8 , 132.5 , 131.7 , 128.4 , 125.7 , 119.6 , 69.4 ; anal . calcd . for c8h4no2 : c , 67.92 ; h , 3.17 ; n , 8.80 .
found : c , 67.91 ; h , 3.19 ; n , 8.88 . under nitrogen atmosphere p - fluoro phenyl magnesium bromide ( 7.5  g , 37.73  mmol )
is added dropwise to a stirred solution of 1-oxo-1,3-dihydro - isobenzofuran-5-carbonitrile 4 ( 5  g , 31.44  mmol ) in thf ( 50  ml ) at 05c .
put in some more thf and wash with water . remove off thf and pour residue 5 into methanol ( 10  ml ) .
nabh4 ( 0.58  g , 15.72  mmol ) is added slowly for 30  min to the reaction mass and stirred for 2  h at r.t .
solvents are removed to get diol 6 which is refluxed with 2n hcl ( 50  ml ) for 2  h. the reaction mass is cooled and diluted with water .
the product is extracted into methylene chloride , washed with water , and dried ( anhy .
the solvent is removed and the residue is crystallized in ipa to provide 1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-carbonitrile 7 as pale yellow solid yielding 5.9  g ( 79% ) , m.p .
97 - 98c ; ir ( kbr pellet , cm ) :  3013(aromatic ch ) , 2246 ( cn ) , 1699 , 1479
( c = c ) , 1038 ( coc ) ; h nmr ( dmso , 400  mhz ) :  7.65 ( s , 1h , arh ) , 7.58 ( d , j = 8.5  hz , 1h , arh ) , 7.31 ( dd , j = 14.0  hz , 2.6  hz , 2h , arh ) , 7.15 ( d , j = 8.5  hz , 1h , arh ) , 7.09 ( t , j = 7.6  hz , 2h , arh ) , 6.11 ( s , 1h , ch ) , 5.29 ( d , j = 2.0  hz , 1h , ch ) , 5.18 ( d , j = 2.0  hz , 1h , ch ) ; c nmr ( dmso , 400  mhz ) :  144.8 , 140.5 , 137.2 , 133.3 , 132.9 , 131.3 , 128.9 , 128.4 , 125.7 , 119.6 , 116.0 , 84.2 , 71.8 ; anal . calcd . for c15h10fno : c , 81.08 ; h , 4.58 ; n , 6.36 .
1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-carbonitrile 7 ( 5  g , 20.92  mmol ) is added to methanol ( 50  ml ) and 1n naoh ( 20  ml ) .
completion of reaction is marked by tlc with mobile phase toluene  :  ethyl acetate = 7.5  :  2.5 . after completion of reaction , the mass is cooled and acidified with 1n hcl .
the solid formed is filtered , washed with water , and recrystalized from ethanol to give 8 as crystalline white solid with a yield of 4.7  g ( 87% ) , m.p .
188190c ; ir ( kbr pellet , cm ) :  3012 ( acid ch ) , 2912 ( acid oh ) , 1707 ( c = o ) , 1682 , 1492 ( c = c ) , 1039 ( coc ) ; h
nmr ( dmso , 400  mhz ) :  12.35 ( bs , 1h , cooh ) , 7.80 ( s , 1h , arh ) , 7.72 ( d , j = 8.5  hz , 1h , arh ) , 7.26 ( dd , j = 14.0  hz , 2.5  hz , 2h , arh ) , 7.13 ( d , j = 8.5  hz , 1h , arh ) , 7.01 ( t , j = 8.0  hz , 2h , arh ) , 6.14 ( s , 1h , ch ) , 5.34 ( d , j = 2.0  hz , 1h , ch ) , 5.21 ( d , j = 2.0  hz , 1h , ch ) ; c nmr ( dmso , 400  mhz ) :  178.2 , 144.8 , 140.8 , 138.1 , 133.2 , 132.0 , 131.7 , 128.9 , 127.9 , 125.4 , 115.6 , 84.7 , 71.2 ; anal .
found : c , 69.70 ; h , 4.24 . 1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-carboxylic acid 8 ( 5  g , 0.019  mol )
the mixture is refluxed for 5  h. the progress of the reaction is monitored by tlc ( toluene  :  ethyl acetate = 7.5  :  2.5 ) . to stop the back reaction , excess of alcohol
ether layer is washed with 5% sodium bicarbonate solution and thereafter evaporated to yield corresponding aromatic ester 9 .
compound 9 ( 4  g , 0.013  mol ) is directly refluxed with 98% hydrazine hydrate ( 4  ml ) in ethanol ( 4  ml ) for 3  h. the progress of the reaction is monitored by tlc ( toluene  :  ethyl acetate  :  diethylamine = 7.5  :  2.5  :  1 ) .
reaction mixture is cooled and the solid formed is filtered and washed with ethanol to get 1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-carbohydrazide 10 as white solid with a yield of 3.6  g ( 94% ) , m.p .
238240c ; ir ( kbr pellet , cm ) :  3185 ( nh ) , 1695 ( c =
n ) , 1083 ( coc ) ; h nmr ( dmso , 400  mhz ) :  11.91 ( s , 1h , nh ) , 11.76 ( s , 2h , nh2 ) , 8.48 ( s , 1h , arh ) , 7.93 ( d , j = 8.5  hz , 1h , arh ) , 7.74 ( dd , j = 14.0  hz , 2.5  hz , 2h , arh ) , 7.42 ( d , j = 8.5  hz , 1h , arh ) , 7.21 ( t , j = 8.0  hz , 2h , arh ) , 6.27 ( s , 1h , ch ) , 5.34 ( d , j = 2.0  hz , 1h , ch ) , 5.21 ( d , j = 2.0  hz , 1h , ch ) ; c nmr ( dmso , 400  mhz ) :  161.0 , 147.8 , 139.7 , 133.8 , 129.5 , 129.1 , 127.5 , 127.1 , 122.6 , 121.3 , 125.0 , 115.9 , 84.5 , 72.8 ; anal . calcd .
for c15h13 fn2o2 : c , 66.17 ; h , 4.81 ; n , 10.29 . found : c , 66.19 ; h , 4.77 ; n , 10.22 .
reflux an equimolar mixture of compound 10 and 4-substituted phenyl isothiocyanate ( a  h ) in methanol ( 10  vol . ) for 3  h. after cooling , the resulting solid is filtered and recrystallized from methanol to afford pure acyl thiosemicarbazides 11(a  h ) .
thiosemicarbazide 11(a  h ) ( 1.0  mmol ) is added portionwise to 5% naoh solution ( 30  ml ) and the reaction mixture is refluxed for 4  h. cool and acidify with 6 n hcl to ph 2 - 3 .
the precipitated solid 12(a  h ) is filtered , washed with water , and recrystallized from ethanol .
( 0.50  g , 1.23  mmol ) we synthesized a white solid 12a ( 0.436  g , 91% ) with m.p .
208210c ; ir ( kbr pellet , cm ) :  3402 ( nh ) , 3085 ( aromatic ch ) , 1604 ( c
= n ) , 1404 ( c = c ) , 1234 ( c = s ) , 1157 ( coc ) , 1033 ( cf ) ; h nmr ( dmso , 400  mhz ) :  14.14 ( s , 1h , nh ) , 7.50 ( s , 1h , arh ) , 7.48 ( d , j = 8.5  hz , 1h , arh ) , 7.37 ( dd , j = 14.0  hz , 2.6  hz , 2h , arh ) , 7.34 ( t , j = 8.0  hz , 2h , arh ) , 7.33 ( d , j = 8.5  hz , 1h , arh ) , 7.187.0 ( m , 5h , arh ) , 6.15 ( s , 1h , ch ) , 5.23 ( d , j = 2.0  hz , 1h , ch ) , 5.17 ( d , j = 2.0  hz , 1h , ch ) ; c nmr ( dmso , 400  mhz ) :  169.0 , 150.9 , 144.4 , 139.7 , 134.9 , 129.9 , 129.8 , 129.1 , 128.9 , 128.8 , 128.2 , 125.8 , 122.6 , 121.9 , 115.8 , 115.6 , 84.3 , 72.7 ; ei - ms ( 110  v ) m / z ( % ) : 390 ( m , 100 ) , 360 ( 6.7 ) , 267 ( 28 ) , 165 ( 2.5 ) , 123 ( 4.3 ) ; anal . calcd . for c22h16
( 0.50  g , 1.19  mmol ) we synthesized a white solid 12b ( 0.432  g , 90% ) with m.p .
194196c ; ir ( kbr pellet , cm ) :  3448 ( nh ) , 3085 ( aromatic ch ) , 2923 ( ch ) , 1654 ( c =
c ) , 1280 ( c = s ) , 1033 ( cf ) ; h nmr ( dmso , 400  mhz ) :  14.11 ( s , 1h , nh ) , 7.53 ( s , 1h , arh ) , 7.37 ( d , j = 8.5  hz , 1h , arh ) , 7.34 ( dd , j = 14.0  hz , 2.5  hz , 2h , arh ) , 7.24 ( t , j = 8.0  hz , 2h , arh ) , 7.19 ( d , j = 8.5  hz , 1h , arh ) , 7.07.11 ( m , 5h , arh ) , 6.21 ( s , 1h , ch ) , 5.28 ( d , j = 2.0  hz , 1h , ch ) , 5.44 ( d , j = 2.0  hz , 1h , ch ) , 2.5 ( s , 2h , ch2 ) ; c nmr ( dmso , 400  mhz ) :  168.5 , 151.7 , 144.8 , 140.0 , 138.8 , 136.2 , 129.9 , 129.1 , 129.0 , 128.4 , 127.9 , 126.0 , 123.0 , 122.1 , 115.9 , 115.6 , 85.4 , 72.7 , 47.1 ; anal . calcd .
for c23h18 fn3os : c , 68.47 ; h , 4.50 ; n , 10.41 . found : c , 68.42 ; h , 4.57 ; n , 10.43 . 

( 0.50  g , 1.15  mmol ) we synthesized a white solid 12c ( 0.413  g , 86% ) with m.p .
212214c ; ir ( kbr pellet , cm ) :  3271 ( nh ) , 3155 ( aromatic ch ) , 1666 ( c =
n ) , 1542 ( c = c ) , 1234 ( c = s ) , 1164 ( coc ) , 1018 ( cf ) ; h
nmr ( dmso , 400  mhz ) :  14.13 ( s , 1h , nh ) , 7.50 ( s , 1h , arh ) , 7.36 ( d , j = 8.5  hz , 1h , arh ) , 7.32 ( dd , j = 14.0  hz , 2.5  hz , 2h , arh ) , 7.29 ( t , j = 8.0  hz , 2h , arh ) , 7.15 ( d , j = 8.5  hz , 1h , arh ) , 7.07.08 ( m , 5h , arh ) , 6.20 ( s , 1h , ch ) , 5.24 ( d , j = 2.0  hz , 1h , ch ) , 5.47 ( d , j = 2.0  hz , 1h , ch ) , 3.6 ( t , j = 7.0  hz , 2h , ch2 ) , 2.51 ( t , j = 7.0  hz , 2h , ch2 ) ; c nmr ( dmso , 400  mhz ) :  169.1 , 150.6 , 144.2 , 140.6 , 135.1 , 129.5 , 129.1 , 128.8 , 128.2 , 127.9 , 126.3 , 125.4 , 122.9 , 121.1 , 115.6 , 115.1 , 85.0 , 72.7 , 48.4 , 33.2 ; anal . calcd . for c24h20 fn3os
: c , 69.04 ; h , 4.83 ; n , 10.06 . found : c , 69.06 ; h , 4.88 ; n , 10.04 . 

( 0.50  g , 1.13  mmol ) we synthesized a white solid 12d ( 0.387  g , 79% ) with m.p .
180182c ; ir ( kbr pellet , cm ) :  3440 ( nh ) , 3093 ( aromatic ch ) , 1612 ( c =
n ) , 1488 ( c = c ) , 1226 ( c = s ) , 1103 ( coc ) , 1033 ( cf ) , 825 ( ccl ) ; h nmr ( dmso , 400  mhz ) :  14.07 ( s , 1h , nh ) , 7.92 ( s , 1h , arh ) , 7.88 ( d , j = 8.5  hz , 1h , arh ) , 7.70 ( d , j = 7.0  hz , 2h , arh ) , 7.64 ( d , j = 7.0  hz , 2h , arh ) , 7.45 ( dd , j = 14.0  hz , 2.5  hz , 2h , arh ) , 7.31 ( t , j = 8.0  hz , 2h , arh ) , 7.25 ( d , j = 8.5  hz , 1h , arh ) , 6.21 ( s , 1h , ch ) , 5.16 ( d , j = 2.0  hz , 1h , ch ) , 5.10 ( d , j = 2.0  hz , 1h , ch ) ; c nmr ( dmso , 400  mhz ) :  169.0 , 152.6 , 147.5 , 144.5 , 139.8 , 138.7 , 134.5 , 131.1 , 129.8 , 128.9 , 128.8 , 128.3 , 125.7 , 122.7 , 115.8 , 155.6 , 84.3 , 72.7 ; anal . calcd . for c22h15 clfn3os : c , 62.34 ; h , 3.57 ; n , 9.91 . found : c , 69.32 ; h , 3.54 ; n , 9.96 . 

( 0.50  g , 1.14  mmol ) we synthesized a white solid 12e ( 0.416  g , 83% ) with m.p .
174176c ; ir ( kbr pellet , cm ) :  3224 ( nh ) , 3091 ( aromatic ch ) , 1612 ( c =
n ) , 1481 ( c = c ) , 1315 ( no2 ) , 1244 ( c = s ) , 1103 ( coc ) ; h
nmr ( dmso , 400  mhz ) :  14.19 ( s , 1h , nh ) , 8.20 ( d , j = 8.0  hz , 2h , arh ) , 7.94 ( s , 1h , arh ) , 7.83 ( d , j = 8.5  hz , 1h , arh ) , 7.42 ( d , j = 8.0  hz , 2h , arh ) , 7.37 ( dd , j = 14.0  hz , 2.5  hz , 2h , arh ) , 7.30 ( t , j = 8.0  hz , 2h , arh ) , 7.24 ( d , j = 8.5  hz , 1h , arh ) , 6.87 ( s , 1h , ch ) , 5.21 ( d , j = 2.0  hz , 1h , ch ) , 5.18 ( d , j = 2.0  hz , 1h , ch ) ; c nmr ( dmso , 400  mhz ) :  168.8 , 153.6 , 150.6 , 143.8 , 137.9 , 134.5 , 129.9 , 129.5 , 129.1 , 128.6 , 127.3 , 125.8 , 124.4 , 122.5 , 117.0 , 115.2 , 84.2 , 72.1 ; anal . calcd . for c22h15 fn4o3s : c , 60.82 ; h , 3.48 ; n , 12.90 . found : c , 60.87 ; h , 3.43 ; n , 12.96 . 
 ( 6 ) synthesis of 4-(4-methylphenyl)-5-[1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-yl]-2h-1,2,4-triazole-3-thione 
 12f . from 11f
( 0.50  g , 1.19  mmol ) we synthesized a white solid 12f ( 0.422  g , 88% ) with m.p .
152154c ; ir ( kbr pellet , cm ) :  3162 ( nh ) , 3044 ( aromatic ch ) , 2948 ( ch ) , 1612 ( c =
n ) , 1472 ( c = c ) , 1226 ( c = s ) , 1146 ( coc ) , 1012 ( cf ) ; h nmr ( dmso , 400  mhz ) :  14.07 ( s , 1h , nh ) , 7.92 ( s , 1h , arh ) , 7.88 ( d , j = 8.5  hz , 1h , arh ) , 7.64 ( d , j = 7.0  hz , 2h , arh ) , 7.58 ( d , j = 7.0  hz , 2h , arh ) , 7.40 ( dd , j = 14.0  hz , 2.6  hz , 2h , arh ) , 7.33 ( t , j = 8.0  hz , 2h , arh ) , 7.26 ( d , j = 8.5  hz , 1h , arh ) , 6.12 ( s , 1h , ch ) , 5.20 ( d , j = 2.0  hz , 1h , ch ) , 5.17 ( d , j = 2.0  hz , 1h , ch ) , 2.33 ( s , 3h , ch3 ) ; c nmr ( dmso , 400  mhz ) :  169.0 , 150.5 , 144.7 , 143.6 , 133.0 , 130.3 , 129.8 , 129.7 , 129.1 , 128.9 , 128.3 , 126.8 , 125.7 , 122.6 , 119.5 , 115.8 , 83.7 , 72.5 , 21.4 ; anal . calcd . for c23h18 fn3os
: c , 68.47 ; h , 4.50 ; n , 10.41 . found : c , 68.42 ; h , 4.56 ; n , 10.47 . 

( 7 ) synthesis of 4-(4-methoxyphenyl)-5-[1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-yl]-2h-1,2,4-triazole-3-thione 
 12 g . from 11 g ( 0.50  g , 1.14  mmol ) we synthesized a white solid 12 g ( 0.403  g , 84% ) with m.p .
174176c ; ir ( kbr pellet , cm ) :  3210 ( nh ) , 3093 ( aromatic ch ) , 1646 ( c =
n ) , 1428 ( c = c ) , 1305 ( co ) , 1278 ( c = s ) , 1140 ( coc ) , 1005 ( cf ) ; h
nmr ( dmso , 400  mhz ) :  14.10 ( s , 1h , nh ) , 7.99 ( s , 1h , arh ) , 7.85 ( d , j = 8.5  hz , 1h , arh ) , 7.44 ( dd , j = 14.0  hz , 2.6  hz , 2h , arh ) , 7.32 ( t , j = 8.0  hz , 2h , arh ) , 7.24 ( d , j = 8.5  hz , 1h , arh ) , 7.11 ( d , j = 7.5  hz , 2h , arh ) , 6.79 ( d , j = 7.5  hz , 2h , arh ) , 6.44 ( s , 1h , ch ) , 5.29 ( d , j = 2.0  hz , 1h , ch ) , 5.01 ( d , j = 2.0  hz , 1h , ch ) , 3.11 ( s , 3h , och3 ) ; c nmr ( dmso , 400  mhz ) :  168.4 , 150.4 , 150.1 , 144.7 , 140.0 , 134.1 , 131.1 , 129.5 , 129.1 , 128.9 , 128.2 , 124.3 , 122.0 , 117.1 , 117.4 , 115.4 , 84.1 , 72.8 , 53.6 ; anal . calcd .
for c23h18 fn3o2s : c , 65.86 ; h , 4.33 ; n , 10.02 . found : c , 65.82 ; h , 4.39 ; n , 10.07 . 

( 0.50  g , 1.05  mmol ) we synthesized a white solid 12h ( 0.398  g , 81% ) with m.p .
206208c ; ir ( kbr pellet , cm ) :  3241 ( nh ) , 3077 ( aromatic ch ) , 1672 ( c =
n ) , 1488 ( c = c ) , 1237 ( c = s ) , 1142 ( coc ) , 1075 ( cf ) , 524 ( cbr ) ; h nmr ( dmso , 400  mhz ) :  14.03 ( s , 1h , nh ) , 7.90 ( s , 1h , arh ) , 7.85 ( d , j = 8.5  hz , 1h , arh ) , 7.66 ( d , j = 7.0  hz , 2h , arh ) , 7.52 ( d , j = 7.0  hz , 2h , arh ) , 7.44 ( dd , j = 14.0  hz , 2.5  hz , 2h , arh ) , 7.32 ( t , j = 8.0  hz , 2h , arh ) , 7.24 ( d , j = 8.5  hz , 1h , arh ) , 6.19 ( s , 1h , ch ) , 5.18 ( d , j = 2.0  hz , 1h , ch ) , 5.12 ( d , j = 2.0  hz , 1h , ch ) ; c nmr ( dmso , 400  mhz ) :  168.1 , 150.6 , 146.2 , 145.1 , 134.6 , 133.2 , 129.9 , 129.5 , 129.0 , 128.8 , 127.1 , 125.7 , 122.4 , 118.4 , 115.2 , 113.6 , 84.3 , 72.6 ; anal . calcd .
for c22h15 br fn3os : c , 56.42 ; h , 3.23 ; n , 8.97 . found : c , 56.44 ; h , 3.26 ; n , 8.91 . as per nccls document m62-a7 protocols , the preliminary antimicrobial activity is performed using the disc diffusion method .
they are bacillus subtilis ( ncim 2063 ) , staphylococcus aureus ( ncim 2079 ) , escherichia coli ( ncim 2574 ) , pseudomonas aeruginosa ( ncim 2036 ) , candida albicans ( ncim 3471 ) , saccharomyces cerevisiae ( ncim 3559 ) , aspergillus flavus ( ncim 1316 ) , and aspergillus niger ( ncim 545 ) . the bacterial strains are maintained on muller - hinton ( mh ) agar medium and fungi are sustained on sabouraud dextrose ( sd ) agar medium .
the bacterial inoculum is prepared by suspending in 9  ml of sterile water for colonies from 24  h culture on mh agar medium . for the fungi ,
the inoculum is prepared with spores derived from 48  h96  h culture on sd agar medium . to standardize the inoculum density for a susceptibility test
the turbidity of the actively growing microbial culture is adjusted with sterile saline to attain turbidity optically comparable to that of the 0.5 mcfarland standards . within 15 minutes after adjusting the turbidity of the inoculum suspension , the petri plates are inoculated with a standardized suspension of the tested microorganisms .
the predetermined series of antimicrobial discs is allotted onto the surface of the inoculated agar plate .
whatman filter paper number 1 is used to prepare discs approximately 6  mm in diameter , which are sterilized in a hot air oven before placing in petri plates .
these paper discs are placed in a circular pattern in each inoculated plate and then injected with the specific amount of tested compound using micropipettes .
all the newly synthesized mercaptotriazoles are dissolved in dimethyl sulfoxide ( dmso ) to prepare chemicals of stock solution of 10  mg/1  ml for antibacterial study and 25  mg/1  ml for antifungal study .
the plates are incubated and the inhibitory activity is measured ( in mm ) as the diameter of the observed inhibition zones .
the tests are repeated to confirm the findings and the average of the readings is taken into account .
following m62-a7 protocols , broth dilution test by doubling dilution of the antibiotics is carried out to examine the minimum inhibitory concentration of the most promising compound 12d against the tested microbes .
the antibacterial and antifungal assays are performed in mueller - hinton broth and sabouraud dextrose broth , respectively .
mic for microbes is to be observed between 250  g/1  ml and 7.81  g/1  ml .
gentamicin ( 1  mg/2  ml ) and fluconazole ( 1  mg/2  ml ) are used as standard antibacterial and antifungal drugs , respectively .
4-nitrophthalimide 1 is reduced to 4-aminophthalimide 2 using sncl2/hcl which is converted to 5-amino-3h - isobenzofuran-1-one 3 by employing zn / naoh .
compound 4 , commonly called 5-cyanophthalide , is subjected to grignard reaction with 4-fluorophenyl magnesium bromide in tetrahydrofuran and the resulting product is treated with sodium borohydride to obtain the diol 6 , which is cyclized with 2n hcl to afford 1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-carbonitrile 7 .
the synthesized acid hydrazide is treated with different substituted phenyl isothiocyanates ( a  h ) to yield 1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-acyl thiosemicarbazides 11(a  h ) .
cyclodehydration of the thiosemicarbazides 11(a  h ) in basic medium ( 5% naoh ) leads to the formation of 4-substituted phenyl-5-[1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-yl]-2h-1,2,4-triazole-3-thiones 12(a  h ) ( scheme 1 ) .
the ir spectra of the mercaptotriazoles 12(a  h ) mark the absence of carbonyl absorption around 1750  cm .
the existence of triazoles in thione form is indicated by the absence of sh stretching in the characteristic region of 2540  cm .
the h nmr spectrum of every compound unveils the deshielding of nh of the triazole ring as anticipated in the range  14.0014.50 .
the signal for nh appearing downfield than  12.0 authenticates the existence of the ring in thione form .
the characteristic fluorocoupling is observed for the aromatic protons of the phenyl ring attached to the 1st position of isobenzofuran moiety . in the c nmr spectra of triazol-3-thiones ,
values close to  168 and  150 are the characteristic signals for c-3 and c-5 carbons , respectively .
disappearance of signal around  161163 for carbonyl carbons indicates the formation of target compounds 12(a  h ) .
the molecular ion peak in the mass spectrum of c22h16fn3os ( 12a ) is found to be at m / z 390.09 .
many research articles on heterocycles have explicated the synthesis of 2-amino-5-substituted-1,3,4-thiadiazole derivatives from substituted acyl thiosemicarbazides .
this reaction runs parallel to the preparation of 3-mercapto-1,2,4-triazoles from the same starting material . here
moreover , the use of novel reagents like saccharin and p - toluene sulfonic acid has also failed to afford the required products .
similarly , spectral characterization reveals that 2-substituted acyl thiosemicarbazides have failed to form the required mercaptotriazoles .
greater steric hindrance of the bulky isobenzofuran substituents may be the rationalization for both failures .
the results of the preliminary testing of the antimicrobial activity of the novel compounds are tabulated in tables 1 and 2 .
varying grades of inhibition against the growth of the tested microbes by the synthesized compounds can be noticed .
broadly , the inhibitory activity against the gram - positive bacteria is higher than against the gram - negative bacteria .
compound 12d shows significant inhibition against all the tested microorganisms owing to the presence of chloro group on the benzene ring attached to the 4th position of triazole ring .
the better activity of 12e , 12 g , and 12h can be attributed to the presence of nitro , methoxy , and bromo groups , respectively , at para positions of benzene ring .
compound 12a , which has unsubstituted benzene at 4th position of triazole ring , also shows better activity than the triazoles with benzyl and phenylethyl groups .
the fluoro substituent attached to the para position of benzene ring , which is connected to the 1st position of the isobenzofuran core , appears to be the reason behind the antimicrobial activities displayed by the target compounds .
minimum inhibitory concentration ( mic ) is inspected for 12d by broth dilution approach . for gram - positive bacteria , the values are less than 62.5 , but for gram - negative bacteria the results are 125  mic > 62.5 .
structural confirmation is done with analytical techniques and antimicrobial action is performed by disc diffusion method . based on structural activity relationship study , compounds 12a , 12d ,
 the paper describes a convenient method for the preparation of 4-substituted phenyl-5-[1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-yl]-2h-1,2,4-triazole-3-thiones . 
 the structures of the synthesized compounds are established by the results of lcms , 1h nmr , 13c nmr , and ir and elemental analyses . 
 the mercaptotriazoles are indicated to be in thione form by 1h nmr spectra . 
 all the synthesized compounds have been screened for antibacterial and antifungal activities . 
 compounds 12d and 12h exhibit encouraging results , while the remaining compounds show moderate activities . on the basis of spectral studies , formation of 2-amino-1,3,4-thiadiazoles from the isobenzofuran acyl thiosemicarbazides 11(a  h ) is ruled out . 
1. Introduction
2. Materials and Methods
3. Results and Discussion
4. Conclusion