January 2013
Synthesis and Antimicrobial Activity of 2‐(Pyridine‐3‐yl)‐4H‐
chromen‐4‐one Derivatives
151
dry pyridine (15 mL) and POCl3 (4.71 g, 0.037 mmol) was
added drop wise at 0°C. The reaction mixture was irradiated
for about 3–4 h under ultrasound. After completion of the
reaction, it was poured on crushed ice and the solid obtained
was dissolved in ethyl acetate (25 mL) and washed with
saturated solution of NaHCO3. The organic layer was dried
over anhydrous sodium sulphate and was concentrated under
reduced pressure.
General procedure for the synthesis of compounds (4e).
Compound 3e (2.25 g, 0.078 mmol) was dissolved in dry
pyridine (10 mL). To this powdered KOH (0.87 g, 0.015
mmol) was added and the reaction mixture was irradiated
for 2–3 h under ultrasound. The reaction mixture was
poured on ice cold water and acidified with conc. HCl.
The yellow solid obtained was filtered off and crystallized
C15H12ClNO3. C, 62.19; H, 4.17; N, 4.83. Found: C,
61.93; H, 3.99; N, 4.55.
1‐(5‐Chloro‐2‐hydroxyphenyl)‐3‐(pyridine‐3‐yl)propane‐1,3‐
1
dione (4e). Yellow solid. mp 131–133°C. H‐NMR (400
MHz, CDCl3‐d6): δ = 6.79 (dd, 1H, Ar–H), 6.89 (d, 1H,
Ar–H), 7.14 (dd, 1H, Ar–H), 7.36 (dd, 1H, Ar–H), 7.57
(d, 1H, Ar–H), 8.53 (m, 1H, Ar–H), 8.98 (s, 1H, vinylic
proton), 9.34 (d, 1H, Ar–H), 12.64 (s, 1H, OH), 15.41 (s,
1H, Enolic‐OH). EC–MS: 276.05 (M+1) and 378.09
(M+3). IR (KBr) cm−1: 3345(-OH), 2949 (Ar–H), 1700
(C═O), 1615 (C═N), 759 (Ar–Cl). Elemental analysis
Calcd. for C14H10ClNO3. C, 60.99; H, 3.66; N, 5.08.
Found: C, 61.24; H, 3.37; N, 4.78.
1‐(5‐Fluoro‐2‐hydroxyphenyl)‐3‐(pyridine‐3‐yl)propane‐1,3‐
1
dione (4f). Yellow solid. mp 117–120°C. H‐NMR (400
MHz, DMSO‐d6): δ = 5.98 (dd, 1H, Ar–H), 7.08 (d, 1H,
Ar–H), 7.12 (dd, 1H, Ar–H), 7.48 (d, 1H, Ar–H), 7.58
(dd, 1H, Ar–H), 7.96 (m, 1H, Ar–H), 8.49 (dd, 1H, Ar–H),
8.79 (s, 1H, vinylic proton), 12.61 (s, 1H, OH), 15.57 (s, 1H,
Enolic‐OH). EC–MS: 270.09 (M+1). IR (KBr) cm−1:
3398 (-OH), 1572 (C═C), 1219 (C═O), 1488 (C═N).
Elemental analysis Calcd. for C14H10FNO3. C, 64.86; H,
from ethanol to obtain pure product.
1‐(2‐Hydroxyphenyl)‐3‐(pyridine‐3‐yl)propane‐1,3‐dione
(4a). Yellow solid. mp 109–111°C. 1H‐NMR (400 MHz,
CDCl3‐d6): δ = 6.32 (d, 1H, Ar–H), 6.89 (dd, 1H, Ar–H), 7.10
(dd, 1H, Ar–H), 7.31 (m, 1H, Ar–H), 7.54 (dd, 1H, Ar–H), 7.56
(d, 1H, Ar–H), 8.49 (m, 1H, Ar–H), 8.99 (dd, 1H, Ar–H), 9.26
(s, 1H, vinylic proton), 12.67 (s, 1H, OH), 15.45 (s, 1H,
Enolic‐OH). EC–MS: 242.05 (M+1). IR (KBr) cm−1:
3340 (-OH), 2933 (Ar–H), 1705 (C═O), 1612 (C═N).
Elemental analysis Calcd. for C14H11NO3. C, 69.70; H, 4.60;
N, 5.81. Found: C, 69.44; H, 4.38; N, 5.52.
3.89; N, 5.40. Found: C, 64.58; H, 3.62; N, 5.89.
1‐(2‐Hydroxy‐5‐methylphenyl)‐3‐(pyridine‐3‐yl)propane‐
1,3‐dione (4g). Yellow solid. mp 116–118°C. 1H‐NMR (400
MHz, CDCl3‐d6): δ = 2.31 (s, 3H, CH3), 6.85 (dd, 1H, Ar–
H), 7.26 (dd, 1H, Ar–H), 7.43 (d, 1H, Ar–H), 7.46 (d, 1H,
Ar–H), 7.55 (dd, 1H, Ar–H), 8.24 (m, 1H, Ar–H), 8.77 (s,
1H, vinylic proton), 9.16 (d, 1H, Ar–H), 11.80 (s, 1H,
OH), 15.49 (s, 1H, Enolic‐OH). EC–MS: 238.04 (M+1).
IR (KBr) cm−1: 3498 (-OH), 1575 (C═C), 1215 (C═O),
1490 (C═N). Elemental analysis Calcd. for C15H13NO3. C,
70.58; H, 5.13; N, 5.49. Found: C, 70.96; H, 4.85; N, 5.20.
General procedure for the synthesis of the compounds (5e).
Compound 4e (1.0 g, 0.002 mol) was dissolved in gla.
acetic acid (5 mL) in a round bottom flask and reaction
mixture was irradiated under ultrasonication at 65°C for
about 15 min. After completion of the reaction (monitored
by TLC), it was cooled to the room temperature and
poured on crushed ice. The solid obtained was filtered and
crystallized from ethanol to get pure product.
2‐(Pyridine‐3‐yl)‐4H‐chromen‐4‐one (5a). Creamy color.
1H‐NMR (400 MHz, DMSO‐d6): δ = 6.88 (dd, 1H, Ar–H),
7.22 (dd, 1H, Ar–H), 7.24–7.26 (m, 2H, Ar–H), 7.73 (dd,
1H, Ar–H), 7.76 (m, 1H, Ar–H), 7.98 (dd, 1H, Ar–H), 8.09
(s, 1H, Ar–H), 8.14 (d, 1H, Ar–H). EC–MS: 224.09 (M+1).
IR (KBr) cm−1: 1685 (γ‐pyrone), 1602 (Ar–O–Ar), 1608
(C═N). Elemental analysis Calcd. for C14H9NO2: C, 75.33;
H, 4.06; N, 6.27. Found: C, 75.70; H, 3.87; N, 5.98.
1‐(3,5‐Dichloro‐2‐hydroxyphenyl)‐3‐(pyridine‐3‐yl)propane‐
1,3‐dione (4b). Yellow solid. mp 105–107°C. H‐NMR
1
(400 MHz, CDCl3‐d6): δ = 6.93 (dd, 1H, Ar–H), 7.12
(d, 1H, Ar–H), 7.26 (d, 1H, Ar–H), 7.47 (dd, 1H, Ar–H),
7.92 (m, 1H, Ar–H), 8.23 (s, 1H, vinylic proton), 8.99 (d,
1H, Ar–H), 12.72 (s, 1H, OH), 15.35 (s, 1H, Enolic‐OH).
EC–MS: 310.03 (M+1) and 312.06 (M+3). IR (KBr) cm−1:
3350 (-OH), 2952 (Ar–H), 1698 (C═O), 1612 (C═N), 761
(Ar–Cl). Elemental analysis Calcd. for C14H9Cl2NO3. C,
54.22; H, 2.93; N, 4.52. Found: C, 53.94; H, 2.65; N, 4.25.
1‐(2‐Hydroxy‐3,5‐dimethylphenyl)‐3‐(pyridine‐3‐yl)propane‐
1,3‐dione (4c). Yellow solid. mp 130–132°C. 1H‐NMR
(400 MHz, CDCl3‐d6): δ = 2.40 (s, 3H, CH3), 2.51 (s, 3H,
CH3), 6.82 (dd, 1H, Ar–H), 6.92 (d, 1H, Ar–H), 7.06
(d, 1H, Ar–H), 7.34 (dd, 1H, Ar–H), 7.82 (m, 1H, Ar–H),
8.53 (s, 1H, vinylic proton), 8.89 (d, 1H, Ar–H), 12.93
(s, 1H, OH), 15.59 (s, 1H, Enolic‐OH). EC–MS: 270.08
(M+1). IR (KBr) cm−1: 3348 (-OH), 2943 (Ar–H), 1709
(C═O), 1614 (C═N). Elemental analysis Calcd. for C16H15NO3.
C, 71.36; H, 5.61; N, 5.20. Found: C, 70.98; H, 5.44; N, 4.93.
1‐(5‐Chloro‐2‐hydroxy‐4‐methylphenyl)‐3‐(pyridine‐3‐yl)
propane‐1,3‐dione (4d). Yellow solid. mp 123–125°C. 1H‐NMR
(400 MHz, CDCl3‐d6): δ = 2.54 (s, 3H, CH3), 6.85 (dd, 1H,
Ar–H),), 6.90 (s, 1H, Ar–H), 7.61 (s, 1H, Ar–H), 7.82 (dd,
1H, Ar–H), 8.51 (m, 1H, Ar–H), 8.89 (s, 1H, vinylic proton),
9.37 (d, 1H, Ar–H), 12.04 (s, 1H, OH), 15.52 (s, 1H,
Enolic‐OH). EC–MS: 290.10 (M+1) and 392.06 (M+3).
IR (KBr) cm−1: 3342 (-OH), 2943 (Ar–H), 1702 (C═O),
1610 (C═N), 757 (Ar–Cl). Elemental analysis Calcd. for
6,8‐Dichloro‐2‐(pyridine‐3‐yl)‐4H‐chromen‐4‐one (5b). Brown
1
color. H‐NMR (400 MHz, CDCl3‐d6): δ = 6.47 (d, 1H,
Ar–H), 7.25 (dd, 1H, Ar–H),7.37 (d, 1H, Ar–H), 7.41 (d, 1H,
Ar–H), 7.53 (m, 1H, Ar–H), 7.98 (dd, 1H, Ar–H), 8.54 (s,
1H, Ar–H). EC–MS: 292.05 (M+1) and 293.11 (M+3). IR
(KBr) cm−1: 1685 (γ‐pyrone), 1602 (Ar–O–Ar),1608 (C═N).
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet