224
V. Satam, R. Rajule, S. Bendre, P. Bineesh, and V. Kanetkar
Vol 46
obtained was purified by vacuum distillation to afford golden
yellow oil, 6.35 g (84%), bp 142–144ꢀC at 2 mm.
polyester fabrics were stitched between two pieces of
undyed polyester fabrics (stain cloths) and treated at
200ꢀC for 1 min. Any staining on the undyed piece,
change in tone, or loss in depth was assessed on a 1
(poor) to 5 (very good) rating.
Synthesis of 1,4-diethyl-7-methoxy-1,2,3,4-tetrahydro-6-
quinoxalinecarboxaldehyde (6). Phosphorous oxychloride
(8.0 mL, 0.09 mol) was added to dimethyl formamide (10.1
mL, 0.13 mol) at 5ꢀC under stirring. After 15 min, 1,4-diethyl-
6-methoxy-1,2,3,4-tetrahydroquinoxaline (11.0 g, 0.05 mol)
was added to the cooled reagent under stirring. The mixture
was then heated at 70–80ꢀC for 4 h and poured on ice water.
The clear solution was neutralized by adding cold sodium hy-
droxide solution (15%) maintaining the temperature at 10–
15ꢀC. The sticky mass obtained was extracted in ethyl acetate
(4 Â 100 mL). Ethyl acetate extracts were combined, dried
over anhydrous sodium sulfate, and vacuum evaporated.
Brown sticky solid showing dark yellow spot on TLC was
purified by column chromatography using neutral activated
aluminum oxide (Eluent: 40% ethyl acetate in hexane), 8.43 g
All the dyes built up well on polyester to give strong,
bright colors. The light fastness of the dyes was of gen-
erally good order and varied from 3 to 6, dye 8e exhib-
ited excellent light fastness. The sublimation fastness of
the dyes was in the range of 2–4, thus showed good
sublimation fastness properties on polyester fabric. The
dyes showed good wash fastness, as it is usual with dis-
perse dyes.
(68%), bp 146–148ꢀC, IR: CO 1712 cmÀ1 1H NMR: d 1.16
,
(t, 6.9Hz, 3H, CH3), d 1.23 (t, 6.9Hz, 3H, CH3), d 3.13–3.18
(m, 2H), d 3.31 (q, 6.9Hz, 2H, CH2), d 3.41 (q, 6.9Hz, 2H,
CH2), d 3.49–3.54 (m, 2H), d 3.93 (s, 3H, OCH3), d 6.0 (s,
1H, phenyl proton), d 7.0 (s, 1H, phenyl proton), d 10.20 (s,
1H, aldehydic proton), Anal. Calcd for C14H20N2O2: C, 67.71;
H, 8.12; N, 11.28. Found: C, 67.81; H, 8.14; N, 11.34.
EXPERIMENTAL
All melting points were uncorrected and in degree Celsius
(ꢀC). IR spectra were recorded on a Bomem Hartmann and
Braun MB-Series FIIR spectrometer (KBr). 1H NMR spectra
were recorded on Varian 300 MHz mercury plus spectrometer,
and chemical shifts are expressed in d ppm using TMS as an
internal standard. Microanalysis for C, H, and N were per-
formed on Thermofignnin Elemental analyzer. Electronic spec-
tra were recorded on Spectronic spectrophotometer from dye
solutions in DMF, methanol, acetone, and acetonitrile. Ther-
mogravimetric analysis was carried out on SDT Q600 v8.2
Build 100 model of TA instruments.
Synthesis of 6-methoxyquinoxaline (4). 4-Methoxy-2-nitro-
aniline (16.8 g, 0.1 mol) was dissolved in methanol (200 mL)
and hydrogenated in Parr hydrogenator using 10% Pd/C
catalyst at 60ꢀC for 6 h (reaction monitored on TLC). After
cooling, the reaction mass was filtered to separate catalyst and
concentrated in roto-evaporator. Residue obtained was dis-
solved in dry acetonitrile (350 mL) and to this solution was
added glyoxal (40%, 32.0 mL, 2.6 mol). Reaction mixture was
then stirred at 60ꢀC for 6 h and cooled. Solvent was removed
in roto-evaporator and the dark brown sticky solid obtained
was passed over silica gel column to remove base impurities
(Eluent: 70% ethyl acetate in hexane). 6-Methoxyquinoxaline
was obtained as white solid in excellent yield, 13.6 g (85%),
mp 58–60ꢀC (Lit mp 60ꢀC [18]).
Synthesis of 1,4-diethyl-6-methoxy-1,2,3,4-tetrahydroqui-
noxaline (5). 6-Methoxyquinoxaline (5.5 g, 0.034 mol) was
dissolved in dry benzene (350 mL) and cooled to 5ꢀC. To this
cold solution was added sodium borohydride (13.2 g, 0.35
mol) over a period of 15 min. Pale yellow slurry thus obtained
was stirred for 10 min. Glacial acetic acid (57.3 mL, 60 g, 1.0
mol) was added to it drop wise over a period of 1 h maintain-
ing the temperature 5–10ꢀC. The brownish slurry that formed
was stirred for another 1 h at 10ꢀC and allowed to attain room
temperature. It was then heated to gentle reflux for 5 h (reac-
tion monitored on TLC). On cooling, thick red resinous mass
was obtained to which water (250 mL) was added. The ben-
zene layer formed was separated and the aqueous layer was
extracted with ethyl acetate (3 Â 100 mL). Combined extracts
and benzene layer were washed repeatedly with dilute sodium
carbonate solution and water, dried over anhydrous sodium
sulfate, filtered and vacuum evaporated. The dark brown oil
Synthesis of styryl dyes (8a–8f).
Synthesis of 2-cyano-3-(1,4-diethyl-7-methoxy-1,2,3,4-tet-
rahydroquinoxalin-6-yl)-2-propenoic acid ethylester (8b). 1,4-
Diethyl-7-methoxy-1,2,3,4-tetrahydro-6-quinoxalinecarboxalde-
hyde (2.48 g, 0.01 mol) and ethyl cyanoacetate 1.13 g (0.01
mol) were dissolved in dry ethanol. Piperidine (0.1 mL) was
added to it and reaction mixture was refluxed for 2 h. Ethanol
was removed by distillation and reddish crystals were washed
with water and dried. Dye (8b) thus obtained was further puri-
fied by column chromatography using neutral activated alumi-
num oxide (Eluent: 30% ethyl acetate in hexaÀn1e), 2.7 g, 78%,
mp 128–132ꢀC, IR: CO 1755, CN 2210 cm
,
1H NMR: d
1.21 (t, 6.9Hz, 3H, CH3), d 1.26 (t, 6.9Hz, 3H, CH3), d 1.36
(t, 6.9Hz, 3H, CH3), d 3.16–3.22 (m, 2H), d 3.34 (q, 6.9Hz,
2H, CH2), d 3.44 (q, 6.9Hz, 2H, CH2), d 3.53–3.59 (m, 2H), d
3.92 (s, 3H, OCH3), d 4.44 (q, 6.9Hz, 2H, CH2), d 6.0 (s, 1H,
phenyl proton), d 7.7 (s, 1H, phenyl proton), d 8.6 (s, 1H, ole-
finic proton), Anal. Calcd for C19H25N3O3: C, 66.45; H, 7.34;
N, 12.24. Found: C, 66.56; H, 7.35; N, 12.31.
Synthesis of 2-cyano-3-(1,4-diethyl-7-methoxy-1,2,3,4-tetra-
hydroquinoxalin-6-yl)-2-propenamide (8a). 2.54 g (81%), mp
1
172–175ꢀC, IR: CO 1685, CN 2218 cmÀ1, H NMR: d 1.20 (t,
7.1Hz, 3H, CH3), d 1.25 (t, 7.1Hz, 3H, CH3), d 3.18–3.23 (m,
2H), d 3.35 (q, 6.9Hz, 2H, CH2), d 3.44 (q, 6.9Hz, 2H, CH2),
d 3.54–3.59 (m, 2H), d 3.90 (s, 3H, OCH3), d 5.3 (s, 2H,
CONH2 proton), d 6.0 (s, 1H, phenyl proton), d 7.6 (s, 1H,
phenyl proton), d 8.5 (s, 1H, olefinic proton), Anal. Calcd for
C17H22N4O2: C, 64.95; H, 7.05; N, 17.82. Found: C, 64.83; H,
7.07; N, 17.99.
Synthesis of [(1,4-diethyl-7-methoxy-1,2,3,4-tetrahydroqui-
noxalin-6-yl)methylene]propanedinitrile (8c). 2.22 g (75%),
mp 226–228ꢀC, IR: CN 2223 cmÀ1 1H NMR: d 1.22 (t,
,
7.0Hz, 3H, CH3), d 1.28 (t, 7.0Hz, 3H, CH3), d 3.16–3.21 (m,
2H), d 3.33 (q, 7.0Hz, 2H, CH2), d 3.42 (q, 7.0Hz, 2H, CH2),
d 3.52–3.57 (m, 2H), d 3.93 (s, 3H, OCH3), d 6.1 (s, 1H, phe-
nyl proton), d 7.7 (s, 1H, phenyl proton), d 8.9 (s, 1H, olefinic
proton), Anal. Calcd for C17H20N4O: C, 68.89; H, 6.80; N,
18.90. Found: C, 68.99; H, 6.83; N, 18.97.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet