1200
K. J. Jarag, A. R. Jagtap, B. N. Borse, S. R. Shukla, and G. S. Shankarling
Vol 49
sodium hydroxide solution. The mixture was extracted with
ethyl acetate. The organic layer was dried with anhydrous
sodium sulfate and then concentrated on rotary evaporator.
The crude product on purification by column chromatography
using silica gel 100–200 # and ethyl acetate: toluene (5:95) as
eluent system afforded dark yellow solid.
Yield: 75%. FTIR (KBr, cmꢁ1): n∼ = 2800–2900, 3000–3100,
1668, 1591, 1320. 1H-NMR (400 MHz, CDCl3): d = 10.18 (s,1H)
ppm, 7.16–7.32 (m, 10H), 7.08 (s, 1H), 6.05 (s, 1H), 3.82 (s, 3H),
3.57 (t, 2H), 3.45 (t, 2H,), 3.30 (t, 2H), 3.04 (t, 2H), 2.90 (m, 4H).
13C-NMR (100 MHz, CDCl3): d = 186.44, 158.23, 143.02,
139.58, 138.71, 128.86, 128.66, 128.60, 128.59, 128.42,
128.33, 128.05, 126.47, 126.23, 126.00, 125.13, 113.92,
108.46, 92.75, 55.75, 53.31, 53.22, 48.79, 45.78, 32.31, 31.45.
ppm. Mass: m/z 401.33 (M + 1) C26H28N2O29(400.30): Calcd.
C77.97, H 7.05, N 6.99; Found C 78.17, H 6.98, N 7.22.
EXPERIMENTAL
Materials and equipment. All solvents and chemicals
were procured from SD fine chemicals (India) and were used
without further purification. The reactions were monitored by
TLC using 0.25-mm E-Merck silica gel 60 F254 precoated
plates, which were visualized with UV light (254 and 366 nm).
Melting points were measured on a standard melting point
apparatus from Sunder Industrial Products, Mumbai. UV–vis
absorption spectra were recorded on a Spectronic GENEYSIS 2
spectrophotometer instrument from dye solutions in chloroform.
The fluorescence maxima were recorded on a Jasco FP- 1520
1
fluorimeter from dye solutions in chloroform. The H-NMR and
13C-NMR spectra were recorded at 400 and 100 MHz,
respectively, on a Varian Mercury Plus spectrometer Chemical
shifts are expressed in d (ppm) using TMS as an internal
standard. Mass spectral data were obtained with a Micromass
Q-Tof (YA105) spectrometer. Elemental analysis was done on a
Harieus rapid analyzer. Thermogravimetric analysis was carried
out on an SDT 226 Q600 v8.2 Build 100 model of TA
instruments.
Synthesis of 2-((7-methoxy-1,4-diphenethyl-1,2,3,4-tetrahy-
droquinoxalin-6-yl)methylene)malononitrile (7a). 7-Methoxy-
1,4-diphenethyl-1,2,3,4-tetrahydroquinoxaline-6-carbaldehyde
(1.5 g, 3 mmol) and malononitrile (0.247 g, 3.7 mmol) were
dissolved in ethanol. Piperidine (0.1 mL) was added to it, and
reaction mixture was refluxed for 4 h. Ethanol was removed
by distillation under reduced pressure to afford dark red
colored solid. The dye 7a obtained was purified by column
chromatography using silica gel 100–200 mesh and toluene
as eluent system.
Synthesis and characterization.
Synthesis of 6-
methoxyquinoxaline (3). 6-Methoxyquinoxaline (3) was
prepared using reported method [19]. m.p. 58–60ꢀC (Lit: 60ꢀC).
Synthesis of 6-methoxy-1,4-diphenethyl-1,2,3,4-tetrahydro-
quinoxaline (4). 6-Methoxyquinoxaline (5.2 g, 0.032 mol) was
dissolved in dry toluene (250 mL) and cooled to 5ꢀC. To this
cold solution, sodium borohydride (12.33g, 0.32mol) was
added over a period of 30 min. Pale yellow slurry thus
obtained was stirred for 15 min. Phenyl acetic acid (44.2 g,
0.32 mol) was dissolved in 100 mL of toluene and added to
reaction mass dropwise over a period of 1 h maintaining the
temperature 5–10ꢀC. The brownish slurry that formed was
stirred for another 1 h at 10ꢀC and allowed to attain room tem-
perature. It was then heated to gentle reflux for 8 h (reaction
monitored on TLC). On cooling, thick reaction mass was
poured in 250 mL of water. The toluene layer formed was sep-
arated, and the aqueous layer was extracted with ethyl acetate
(3 ꢂ 100 mL). Combined extracts and toluene layer were washed
with 40% potassium hydroxide solution and brine, dried over
anhydrous sodium sulfate, filtered, and vacuum evaporated to
afford dark brown oil.
Yield: 83%, Melting point: 142–145ꢀC. FTIR (KBr): n∼ =
3027, 2203, 1610, 1512, 1338, 1294 cmꢁ1
.
1H-NMR
(400 MHz,CDCl3): d = 8.00 (s, 1H), 7.55 (s, 1H), 7.32–7.35
(m, 4H, J = 8.85 Hz), 7.28–7.30 (m, 4H J = 8.45 Hz), 7.18
(t, 2H) 5.94 (s, 1 H), 3.80 (s, 3 H), 3.62 (t, 2H), 3.46 (t, 2H),
3.28 (t, 2H), 3.04 (t, 2H), 2.92 (t, 4H) ppm. 13C-NMR (CDCl3,
100 MHz): d = 156.68, 150.04, 144.69, 139.80, 138.44, 129.14,
128.99, 128.83, 128.49, 127.02, 126.28, 118.81, 110.02,
107.48, 92.28, 56.07, 53.70, 53.12, 49.42, 46.24, 32.83, 31.90
ppm. Mass: m/z 449 (M + 1). C29H28N4O (448): calcd. C 77.65,
H 6.29, N 12.49; found C 77.39, H 5.94, N 12.79.
The following compounds were synthesized by aforemen-
tioned procedure, using compound 5 and different active methy-
lene compounds 6b–6e.
Synthesis of (E)-ethyl 2-cyano-3-(7-methoxy-1,4-diphe-
nethyl-1,2,3,4-tetrahydroquinoxalin-6-yl)acrylate (7b). Dark
red solid, Yield: 62%. Melting point: 137–139ꢀC. IR (KBr):
Yield: 76%. FTIR (KBr, cmꢁ1): n∼
= 3027, 2203,
1610,1512,1338,1294 cmꢁ1. H-NMR (400 MHz, CDCl3): d =
7.19–7.33 (m, 10H) ppm, 6.54 (s, 1H), 6.21–6.24 (dd, 2H, J =
8.43 Hz), 3.77 (s, 3H), 3.37–3.48 (m, 4H,), 3.28 (m, 2H), 3.19
(m, 2H), 2.90 (m, 4H). 13C-NMR (CDCl3, 100 MHz): d =
152.99 ppm, 140.15, 139.83, 129.05, 128.84, 128.76, 128.52,
128.50, 126.58, 126.20, 126.12, 111.90, 100.18, 98.80, 55.54,
54.12, 53.52, 47.95, 47.16, 32.09, 31.92. C25H28N2O: Calcd. C
80.61, H 7.58, N, 7.52; Found C 80.63, H 7.78, N, 7.65.
n∼ = 3022, 2206, 1697, 1514, 1346, 1234 cmꢁ1 1H-NMR
,
1
(400 MHz, CDCl3): d = 8.63 (s, 1H), 7.81 (s, 1H), 7.20–7.31
(Ar-H, 10H), 6.00 (s, 1 H), 4.32 (q, 2H), 3.81 (s, 3H), 3.60
(t, 2H), 3.51 (t, 2H), 3.30 (t, 2H), 3.07 (t, 2H), 2.94 (m, 4H),
1.37 (t, 3H) ppm. 13C-NMR (100 MHz, CDCl3): d = 156.68,
150.04, 144.69, 139.80, 138.44, 129.14, 128.99, 128.83,
128.49, 127.02, 126.28, 118.81, 110.02, 107.48, 92.28, 56.07,
53.70, 53.12, 49.42, 46.24, 32.83, 31.90 ppm. Mass: m/z = 496
(M + 1). C31H33N3O3(495): calcd. C 75.13, H 6.71, N 8.48;
found C 75.45, H 6.40, N 8.84.
Synthesis of 7-methoxy-1,4-diphenethyl-1,2,3,4-tetrahydro-
quinoxaline-6-carbaldehyde (5). In a 100 mL three neck
round bottom flask (4.1 mL, 53 mmol) of anhydrous N,N-
dimethylformamide was cooled (0–5ꢀC) in an ice bath. To
this solution, (3.39 mL, 36 mmol) of phosphorous oxychloride
was added dropwise at 0–5ꢀC. 6-Methoxy-1,4-diphenethyl-
1,2,3,4-tetrahydroquinoxaline (4) (7.65 g, 20 mmol) was added
to the above solution and heated to 70ꢀ C for 5 h. This solution
was then cooled to room temperature, poured in to ice water, and
neutralized to pH 6–7 by dropwise addition of saturated aqueous
(E)-methyl 2-cyano-3-(7-methoxy-1,4-diphenethyl-1,2,3,4-
tetrahydroquinoxalin-6-yl)acrylate (7c). Yield: 80%. Melting
point: 124–127ꢀC. IR (KBr): n∼ = 3021, 2203, 1696, 1514,
1347, 1234 cmꢁ1. 1H-NMR (400 MHz, CDCl3): d = 8.63 (s, 1H),
7.80 (s, 1H), 7.18–7.27 (Ar-H, 10H), 6.00 (s, 1 H), 3.80 (s, 3H),
3.60 (t, 2H), 3.51 (t, 2H), 3.30 (t, 2H), 3.07 (t, 2H), 2.94 (m, 4H),
1.37 (t, 3H) ppm. 13C-NMR (100 MHz, CDCl3): d = 156.80,
147.24, 143.37, 140.08, 138.74, 129.22, 128.92, 128.84, 128.44,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet