January 2010
Unusual Anisotropic Effects from 1,3-Dipolar Cycloadducts
of 4-Azidomethyl Coumarins
95
EXPERIMENTAL
6.53 (s, 1H, C3AH), 6.96 (d, 1H, C7AH, J ¼ 8.1 Hz), 7.26
(d, 1H, C8AH, J ¼ 8.1 Hz), 7.40 (s, 1H, C5AH). Anal. Calcd.
for C11H9N3O3; C, 57.14; H, 3.92; N, 18.17; Found: C, 57.11;
H, 3.83; N, 18.06.
Melting points were determined by open capillary method
and are uncorrected. The elemental analysis was performed
using Heraus CHN rapid analyzer. Analytical TLC was per-
formed on Merck precoated 60 F254 silica gel plates. IR spec-
tra (KBr disc) were recorded on a Nicolet-5700 FTIR spectro-
4-Azidomethyl-7-methoxy-chromen-2-one (2f). Colorless
solid (petroleum ether), mp. 92ꢀC, yield 59%; IR (KBr, m in
1
cmꢁ1): 1712 (lactone C¼¼O), 2116 (N3); H NMR (300 MHz,
photometer. H and 13C NMR spectra were recorded on Bruker
1
CDCl3): d 3.93 (s, 3H, C7AOCH3), 4.61 (s, 2H, CH2AN3),
6.53 (s, 1H, C3AH), 6.55–7.44 (m, 3H, ArAH). Anal. Calcd.
for C11H9N3O3; C, 57.14; H, 3.92; N, 18.17; Found: C, 57.09;
H, 3.86; N, 18.02.
300 MHz spectrometer using CDCl3 as a solvent and tetrame-
thylsilane as an internal standard. The chemical shifts are
expressed in d ppm scale down field from tetramethylsilane
and proton signals are indicated as s ¼ singlet, d ¼ doublet, t
¼ triplet and m ¼ multiplet. EI 70 EV and AUTOSPEC elec-
tron impact mass spectrometer was used to record mass
spectra.
Preparation of substituted 4-bromomethylcoumarins (1a–
1h). The required substituted 4-bromomethylcoumarins 1 [14]
have been synthesized by the Pechmann cyclization of various
phenols with 4-bromoethylacetoacetate.
4-Azidomethyl-6-chloro-chromen-2-one (2g). Colorless solid
(petroleum ether), mp. 118ꢀC, yield 66%; IR (KBr, m in
1
cmꢁ1): 1720 (lactone C¼¼O), 2121 (N3); H NMR (300 MHz,
CDCl3): d 4.55 (s, 2H, CH2AN3), 6.58 (s, 1H, C3AH), 7.32
(d, 1H, C7AH, J ¼ 8.2 Hz), 7.54 (d, 1H, C8AH, J ¼ 8.2 Hz),
7.70 (s, 1H, C5AH); LCMS m/z: 237 [M þ 2]. Anal. Calcd.
for C10H6ClN3O2; C, 50.97; H, 2.57; N, 15.05; Found: C,
50.82; H, 2.54; N, 15.01.
General procedure for the preparation of 4-azidomethyl-
chromen-2-ones (2a–2h). 4-Bromo-methylcoumarin 1 (0.01
mol) was taken in acetone (20 mL) in a round bottom flask.
To this, sodium azide (0.012 mol) in 3 mL of water was added
dropwise with stirring. The stirring was continued for 10 h
(reaction was monitored by TLC). Then, the reaction mixture
was poured to ice cold water. The separated solid was filtered
and recrystallized using suitable solvent (Table 4).
4-Azidomethyl-7-chloro-chromen-2-one (2h). Colorless solid
(petroleum ether), mp. 102ꢀC, yield 65%; IR (KBr, m in
1
cmꢁ1): 1710 (lactone C¼¼O), 2120 (N3); H NMR (300 MHz,
CDCl3): d 4.54 (s, 2H, CH2AN3), 6.56 (s, 1H, C3AH), 7.21
(d, 1H, C6AH, J ¼ 8.1 Hz), 7.41 (s, 1H, C8AH), 7.71 (d, 1H,
C5AH, J ¼ 7.9 Hz). Anal. Calcd. for C10H6ClN3O2; C, 50.97;
H, 2.57; N, 15.05; Found: C, 50.91; H, 2.52; N, 15.00.
General procedure for the preparation of 1-(2-oxo-2H-
chromen-4-ylmethyl)-1H-[1,2,3]triazole-4,5-dicaboxylic acid
dimethyl ester (3a–3h). Mixture of 4-azidomethylcoumarin 2
(0.01 mol) and DMAD (0.01 mol) was taken in a dry xylene
(5 mL) in a round bottom flask. The mixture was refluxed in
an oil bath at 130ꢀC under dry conditions for 8 h (reaction
was monitored by TLC) and then cooled. The separated solid
was collected by filtration and recrystallized using suitable
solvent.
4-Azidomethyl-6-methyl-chromen-2-one (2a). Colorless
solid (ethanol), mp. 110ꢀC, yield 63%; IR (KBr, m in cmꢁ1):
1
1722 (lactone C¼¼O), 2109 (N3); H NMR (300 MHz, CDCl3):
d 2.44 (s, 3H, C6ACH3), 4.57 (s, 2H, CH2AN3), 6.52 (s, 1H,
C3AH), 7.30 (s, 1H, C5AH), 7.32 (d, 1H, C7AH, J ¼ 7.9
Hz), 7.40 (d, 1H, C8AH, J ¼ 8.3 Hz); LCMS m/z: 216 [M þ
1]. Anal. Calcd. for C11H9N3O2; C, 61.39; H, 4.22; N, 19.53;
Found: C, 61.36; H, 4.10; N, 19.51.
4-Azidomethyl-7-methyl-chromen-2-one (2b). Colorless
solid (petroleum ether þ benzene), mp. 104ꢀC, yield 60%; IR
(KBr, m in cmꢁ1): 1732 (lactone C¼¼O), 2098 (N3); 1H NMR
(300 MHz, CDCl3): d 2.47 (s, 3H, C7ACH3), 4.56 (s, 2H,
CH2AN3), 6.47 (s, 1H, C3AH), 7.27 (s, 1H, C8AH), 7.13 (d,
1H, C6AH, J ¼ 8.0 Hz), 7.41 (d, 1H, C5AH, J ¼ 8.0 Hz);
LCMS m/z: 216 [M þ 1]. Anal. Calcd. for C11H9N3O2; C,
61.39; H, 4.22; N, 19.53; Found: C, 61.32; H, 4.08; N, 19.47.
1-Azidomethyl-benzo[f]chromen-3-one (2c). Colorless solid
(ethanol), mp. 146ꢀC, yield 65%; IR (KBr, m in cmꢁ1): 1727
(lactone C¼¼O), 2099 (N3); 1H NMR (300 MHz, CDCl3): d
4.96 (s, 2H, CH2AN3), 6.71 (s, 1H, C3AH), 7.50 (d, 1H,
ArAH, J ¼ 8.8 Hz), 7.58 (t, 1H, ArAH, J ¼ 6.6 Hz), 7.69 (t,
1H, ArAH, J ¼ 6.6 Hz), 7.94 (d, 1H, C7AH, J ¼ 8.1 Hz),
8.02 (d, 1H, ArAH, J ¼ 8.9 Hz), 8.25 (d, 1H, C8AH, J ¼ 8.0
Hz). Anal. Calcd. for C14H9N3O2; C, 66.93; H, 3.61; N, 16.73;
Found: C, 66.90; H, 3.54; N, 16.70.
1-(6-Methyl-2-oxo-2H-chromen-4-ylmethyl)-1H-[1,2,3]tri-
azole-4,5-dicaboxylic acid dimethyl ester (3a). Colorless
solid (ethanol), mp. 192ꢀC, yield 76%; IR (KBr, m in cmꢁ1):
1
1722 (lactone C¼¼O), 1722 (ester C¼¼O); H NMR (300 MHz,
CDCl3): d 2.46 (s, 3H, C6ACH3), 3.95 (s, 3H, ACOOCH3),
4.02 (s, 3H, ACOOCH3), 5.60 (s, 1H, C3AH), 6.05 (s, 2H,
C4ACH2), 7.36 (d, 1H, C7AH, J ¼ 8.4 Hz), 7.51 (d, 1H,
C8AH, J ¼ 8.4 Hz), 7.67 (s, 1H, C5AH); 13C NMR (75 MHz,
CDCl3): 22, 50, 53, 54, 114, 117, 118, 124, 130, 134, 135,
141, 148, 152, 158, 161, 162; LCMS m/z: 358 [M þ 1]. Anal.
Calcd. for C17H15N3O6; C, 57.14; H, 4.23; N, 11.76; Found:
C, 57.18; H, 4.17; N, 11.69.
1-(7-Methyl-2-oxo-2H-chromen-4-ylmethyl)-1H-[1,2,3]tri-
azole-4,5-dicaboxylic acid dimethyl ester (3b). Colorless
solid (benzene), mp. 151ꢀC, yield 75%; IR (KBr, m in cmꢁ1):
1
1722 (lactone C¼¼O), 1754 (ester C¼¼O); H NMR (300 MHz,
CDCl3): d 2.48 (s, 3H, C7ACH3), 3.94 (s, 3H, ACOOCH3),
4.01 (s, 3H, ACOOCH3), 5.67 (s, 1H, C3AH), 6.03 (s, 2H,
C4ACH2), 7.17 (d, 1H, C6AH, J ¼ 7.2 Hz), 7.37 (s, 1H,
C8AH), 7.57 (d, 1H, C5AH, J ¼ 7.1 Hz); LCMS m/z: 358 [M
þ 1]. Anal. Calcd. for C17H15N3O6; C, 57.14; H, 4.23; N,
11.76; Found: C, 57.19; H, 4.16; N, 11.72.
4-Azidomethyl-benzo[h]chromen-2-one (2d). Colorless solid
(ethanol), mp. 131ꢀC, yield 64%; IR (KBr, m in cmꢁ1): 1716
(lactone C¼¼O), 2115 (N3); 1H NMR (300 MHz, CDCl3): d
4.63 (s, 2H, CH2AN3), 6.57 (s, 1H, C3AH), 7.26–8.54 (m,
6H, ArAH). Anal. Calcd. for C14H9N3O2; C, 66.93; H, 3.61;
N, 16.73; Found: C, 66.87; H, 3.53; N, 16.66.
1-(3-Oxo-3H-benzo[f]chromen-1-ylmethyl)-1H-[1,2,3]tria-
zole-4,5-dicaboxylic acid dimethyl ester (3c). Colorless solid
(ethanol), mp. 180ꢀC, yield 78%; IR (KBr, m in cmꢁ1): 1731
(lactone C¼¼O), 1731 (ester C¼¼O); 1H NMR (300 MHz,
CDCl3): d 3.85 (s, 3H, ACOOCH3), 4.03 (s, 3H, ACOOCH3),
4-Azidomethyl-6-methoxy-chromen-2-one (2e). Colorless
solid (petroleum ether), mp. 106ꢀC, yield 62%; IR (KBr, m in
1
cmꢁ1): 1710 (lactone C¼¼O), 2115 (N3); H NMR (300 MHz,
CDCl3): d 3.90 (s, 3H, C6AOCH3), 4.57 (s, 2H, CH2AN3),
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet