EXPERIMENTAL
X-ray Structural Analysis of Compound 9. Crystals of 2,2-dimethyl-2,3-dihydrobenzimidazo[1,2-a]-
quinazolin-4(1H)-one 9 are monoclinic, C16H15N3O, at 20°C: a = 6.972(3), b = 8.097(2), c = 22.905(12) Å;
β = 97.85(4)°; V = 1280.9(9) Å3; Mr = 265.31; Z = 4, space group P2(1)/c; dcalc = 1.376 g/cm3;
µ(MoKα) = 0.089 mm-1; F(000) = 560. The unit cell parameters and intensities of 2409 reflections
(2214 independent with Rint = 0.07) were measured on a Siemens P3/PC automatic, four circle diffractometer
(MoKα graphite monochromator, 2θ/θ scanning, 2θmax = 50°).
The structure was solved by a direct method using the SHELX97 program package [17]. The positions
of the hydrogen atoms were revealed in electron density difference synthesis and refined using the "rider" model
with Uiso = nUeq for the non-hydrogen atom bound to the given hydrogen (n = 1.5 for a methyl group and n = 1.2
for the remaining hydrogen atoms). The structure was refined for F2 in full matrix least squares analysis in the
anisotropic approximation for non hydrogen atoms to wR2 = 0.250 for 2214 reflections (R1 = 0.082 for
1181 reflections with F 4σ(F), S = 0.979). The coordinates and equivalent isotropic thermal parameters for the
>
non-hydrogen atoms in the molecule 9 are given in Table. 4.
IR spectra were recorded on a Specord M-82 spectrometer for KBr tablets and NMR spectra on a Varian
300 (300 MHz) spectrometer for solutions in DMSO-d6 with TMS internal standard. Mass spectra were
obtained on a Finnigan M-95 spectrometer with direct introduction of the sample into the ion source. The
ionization chamber temperature was 180°C, ionizing intensity 70 eV, and emission current 100 µA. Monitoring
of the purity of the compounds was carried out by TLC on Silufol UV-254 plates with acetone–chloroform (1:1)
as eluent.
b
A. A
3,3-Dimethyl-12-phenyl-3,4,5,12-tetrahydrobenzimidazo[2,1- ]quinazolin-1(2H)-one (4a).
mixture of 5,5-dimethylcyclohexane-1,3-dione 3 (0.14 g, 1 mmol), benzaldehyde 2a (0.11 g, 1 mmol), and
2-aminobenzimidazole 1 (0.133 g, 1 mmol) in DMF (1 ml) was refluxed for 5 min until the formation of a
crystalline precipitate. The reaction mixture was cooled, 2-propanol (5 ml) was added, and compound 4a
(0.22 g) was filtered off and recrystallized from a mixture of DMF and 2-propanol (1:2).
Compounds 4b,c were prepared similarly using the aldehydes 2b,c.
B. A mixture of compound 6a (0.272 g, 1 mmol) and 2-aminobenzimidazole 1 (0.133 g, 1 mmol) in
DMF (1 ml) was refluxed for 3 min. The reaction mixture was cooled, 2-propanol (5 ml) was added, and the
precipitated product 4a was filtered off to give a yield of 0.21 g (62%). The product was purified by
recrystallization from a mixture of DMF and 2-propanol (1:2). The 4a obtained agreed in spectroscopic
parameters and melting point with the sample synthesized using method A.
C. A mixture of 3,3,6,6-tetramethyl-9-phenyl-3,4,5,6,7,9-hexahydroxanthene-1,8(2H)-dione 7a (0.35 g,
1 mmol) and amine 1 (0.133 g, 1 mmol) in DMF (1 ml) was refluxed for 3-5 min to the appearance of a
precipitate. After cooling, the reaction mixture was treated with 2-propanol (5 ml) and the precipitated product
was filtered off to give compound 4a (0.172 g, 51%). The filtrate was extracted with chloroform and the extract
was dried over sodium sulfate, filtered, and the filtrate evaporated. With the use of methanol, the oily residue
yielded dimedone 3 (0.13 g) with mp 150-151°C (mp 150°C [18]).
Compounds 4b,c were prepared similarly from compounds 7b,c respectively.
a
A mixture of dimedone
3
2,2-Dimethyl-2,3-dihydrobenzimidazo[1,2- ]quinazolin-4(1H)-one (9).
(0.14 g, 1 mmol) and amine 1 (0.133 g, 1 mmol) in DMF (1 ml) was refluxed for 25 min. 2-Propanol (5 ml) was
added to the cooled product which was then filtered to give compound 9 (0.16 g, 60%) and this was
1
recrystallized from 2-propanol. H NMR spectrum, δ, ppm: 8.44-7.51 (4H, m, 8-H to 11-H); 9.08 (1H, s, 5-H);
2.61, 3.70 (2H, s, CH2); 1.21 (6H, s, CH3). Mass spectrum, m/z (I, %): 265 (88), 250 (15), 209 (100), 181 (30),
154 (40), 133 (25), 103 (28), 77 (18), 51 (32).
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