N. Coßskun, M. C¸ etin / Tetrahedron Letters 45 (2004) 8973–8975
8975
2. Experimental
46.17; 90.22; 120.73; 121.03; 122.68; 124.33; 124.54;
126.20; 126.70; 127.40; 128.09; 128.72; 129.24; 129.26;
129.42; 130.00; 135.26; 137.70; 138.21; 139.36; 152.07;
155.80. Anal. Calcd for C28H24N4O3 (464.52): C,
72.40; H, 5.21; N, 12.06. Found: C, 72.35; H, 5.15; N,
12.00.
2.1. Synthesis of 2-aryl-1,2,3,4-tetrahydroquinazolines 1.
General procedure
To a solution of 2-aminobenzylamine (5mmol, 0.611g)
in MeOH (20mL) was added aldehyde (5mmol) and
the reaction mixture stirred for 1h at room temperature.
The solvent was evaporated and the compounds were
recrystallized from ether (1a,b) or ethanol (1c,d).
2.4. Synthesis of diphenylcarbamoylated N-(2-amino-
methyl-phenyl)-hydroxylamine 4
To a solution of compound 3 (0.2mmol) in THF
(10mL), hydrochloric acid (10mL, 2M) was added
and the solution was stirred for 15min. The solution
was extracted with chloroform (3 · 10mL) and the com-
bined extracts were washed with water (2 · 10mL) and
dried over anhydrous Na2SO4. The organic solvent
was removed under vacuum and the residue was tritu-
rated with ether to give compound 4 in quantitative
yield. Mp 165–165.3ꢁC; IR (KBr) mNH 3358; mOH 3159;
2.1.1. 2-Furan-2-yl-1,2,3,4-tetrahydroquinazoline 1b.
Prepared according to the general procedure and recrys-
tallized from ether. H NMR (400MHz, CDCl3): d 2.40
(1H, br s, NH), 3.92 (2H, AB system, J = 16.8), 5.23
(1H, s), 6.27 (3H, m), 6.49 (1H, d, J = 8.0), 6.63 (1H,
t, J = 7.6), 6.83 (1H, d, J = 7.4), 6.95 (1H, t, J = 7.6),
7.32 (1H, s); 13C NMR (100MHz, CDCl3): d 45.91;
64.20; 107.05; 110.68; 115.73; 118.91; 121.83; 126.60;
127.74; 142.74; 143.25; 154.45.
1
mC@O 1646cmÀ1 1H NMR (400MHz, DMSO-d6): d
.
4.38 (2H, d, J = 5.9), 6.50 (1H, t, J = 5.9), 6.9 (1H, t,
J = 7.3), 7.01 (1H, t, J = 7.3), 7.20–7.42 (10H, m), 7.7
(2H, d, J = 6.5), 8.69 (1H, s), 9.33 (1H, s), 10.59 (1H,
s). Anal. Calcd for C21H20N4O3 (376.41): C, 67.01; H,
5.36; N, 14.88. Found: C, 67.10; H, 5.30; N, 14.80.
2.2. 2-Aryl-1,2,3,4-tetrahydroquinazolin-1-ols 2. General
procedure
To a solution of 2-aminobenzylamine (5mmol, 0.611g)
in MeOH (20mL), the aldehyde (5mmol) was added
and the reaction mixture stirred for 1h at room temper-
ature. H2O2 (20mmol, 35%, 1.94g, 1.7mL) and Na2-
WO4Æ2H2O (0.25mmol, 0.075g) were added and the
mixture stirred at room temperature for 1h. The precipi-
tate formed was filtered and washed with methanol and
dried under vacuum. Yield, mp and IR data are given in
Table 1.
Acknowledgements
Uludag University Research Fund is gratefully acknowl-
edged for its financial support (Project No. 2001-2).
References and notes
2.2.1. 2-Phenyl-1,2,3,4-tetrahydroquinazolin-3-ol 2a.
1H NMR (400MHz, DMSO-d6): d 4.03 (2H, AB system,
J = 16.7), 4.92 (1H, s), 6.93 (1H, m), 7.05 (1H, m), 7.23
(2H, m), 7.47 (4H, m), 7.61 (2H, m), 8.89 (1H, s); 13C
NMR (100MHz, CDCl3): d 45.85; 78.85; 118.23;
121.09; 125.53; 126.98; 127.25; 128.25; 128.68; 128.93;
142.49; 150.64. Anal. Calcd for C14H14N2O (226.27):
C, 74.31; H, 6.24; N, 12.38. Found: C, 74.32; H, 5.95;
N, 12.30.
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2.3. 7-Aryl-9H-6-oxa-5,8-diaza-benzocycloheptene-5,8-
dicarboxylic acid bis-phenylamide 3. General procedure
Compound 2 (0.5mmol) was suspended in toluene
(15mL), aryl isocyanate (1mmol) was added and the
mixture stirred for 18h at room temperature. The preci-
pitated product was filtered and dried under vacuum at
room temperature. Yield, mp and IR data are given in
Table 1.
7. Gilchrist, T. L. Six-membered Ring Compounds with Two
or More Heteroatoms. In Heterocyclic Chemistry; Pitman:
London, 1985; pp 327–330.
´ ´
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¨
9. In the case of compounds 1 having aliphatic R the
precipitation of 2 were not observed. The products
resulted from further oxidation of 2.
2.3.1. 7-Phenyl-9H-6-oxa-5,8-diaza-benzocycloheptene-
5,8-dicarboxylic acid bis-phenylamide 3a. 1H NMR
(400MHz, CDCl3): d 4.52 (2H, AB system, J = 17.7),
6.35 (1H, s), 6.93 (1H, m), 7.02 (1H, m), 7.12–7.23
(10H, m), 7.37 (5H, m), 7.53 (2H, m), 7.67 (1H, s), 7.8
(1H, d, J = 7.9). 13C NMR (100MHz, CDCl3): d
10. The value is too high for an aminal proton in the
unexpanded quinazoline structure. If this was the case,
carbamoylation would occur at the oxygen, which should
give a carbonyl frequency at approximately 1740cmÀ1
.