Hence the results discussed above for the acylation indicate that the dihydro-13H-isoquino[3,2-b]-
quinazolinone 1a, which has an imino form in solutions with one nucleophilic center (the nitrogen atom), shows
ambident properties when acylated and forms the N- and C-acylation products depending on the reaction
conditions. Such chemical behavior is typical of secondary enamines. Acylation of compound 1a at the C(6) atom
is associated with its conversion to a mesomeric anion under the action of base with an increase in the
nucleophilicity of a carbon atom and not with the imine-enamine equilibrium.
EXPERIMENTAL
1
IR spectra (KBr tablets) were recorded on a Pye-Unicam SP3-300 instrument. H NMR spectra were
taken on a Varian Mercury 400 (400 MHz) instrument using TMS as internal standard. The mass spectrum of
compound 10 was recorded using HPLC on an AGILENT/100-Series instrument (CI, acetonitrile, 0.05% formic
acid). Melting points were taken on a Boetius heating block and not corrected. Monitoring of the course of the
reactions and the purity of the compounds prepared was undertaken using TLC on Silufol UV-254 plates.
Compounds 1a,b were prepared as in the method [5].
6-{[(4-(Dimethylamino)phenyl]methylidene}-6,11-dihydro-13H-isoquino[3,2-b]quinazolin-13-ones
(3a,b). A mixture of compound 1a,b (4.03 mmol) and aldehyde 2a (0.60 g, 4.06 mmol) in acetic anhydride
(10 ml) was refluxed for 40 min. Solvent was evaporated in vacuo using a rotary evaporator and the residue was
treated with acetone (10 ml). The precipitated product 3a,b was filtered, washed with acetone, and recrystallized
from DMF.
6-[(4-Nitrophenyl)methylidene]-6,11-dihydro-13H-isoquino[3,2-b]quinazolin-13-one hydrobromide
(3g·HBr) was prepared by the method for synthesis of compounds 3a,b from the hydrobromide 1a·HBr (1 g,
3.04 mmol) and aldehyde 2f (0.53 g, 3.5 mmol), washed with acetone, and recrystallized from AcOH.
6-(Arylidene)-6,11-dihydro-13H-isoquino[3,2-b]quinazolin-13-ones (3c-f). Morpholine (0.7 ml,
8.12 mmol) was added to a suspension of compound 1a (1 g, 4.03 mmol) in 2-propanol (10 ml), the mixture was
heated to reflux, the aldehyde 2b-e (5.0 mmol) was added, and the reaction product was refluxed for 6 h.
t-BuOK (0.45 g, 4.06 mmol) and the corresponding aldehyde 2b-e (5 mmol) were added and the product was
refluxed for a further 5 h. Solvent was evaporated, the residue was treated with water (10 ml), and the
precipitated product 3c-f was filtered off, washed with water and 2-propanol, and recrystallized from DMF.
6-(4-Chlorobenzoyl)-5,11-dihydro-13H-isoquino[3,2-b]quinazolin-13-one (6). Compound 1a (1 g,
4.03 mmol) was dissolved with heating in anhydrous pyridine (5 ml). p-Chlorobenzoyl chloride (1.02 ml,
8.0 mmol) was added to the solution and the mixture was refluxed for 4 h. The cooled reaction mixture was
treated with water (20 ml) and the precipitated product 6 was filtered, carefully washed with water and
2-propanol, and recrystallized from DMF.
5,6-Dicyano-5,11-dihydro-13H-isoquino[3,2-b]quinazolin-13-ones (7a-c). Using the method of
synthesis for product 6 from compound 1a and acetic, benzoic, or p-toluic acid chlorides to give the products
7a-c respectively.
6,11-Dihydro-11'H-[6,11']bis[isoquino[3,2-b]quinazolinyl]-13,6',13'-trione (8) was prepared as for
compounds 6, 7 from compound 1a and isonicotinoyl chloride. Yield 65%; mp. 280-281ºC (DMF)
(mp 279-281ºC [6]).
5-Acetyl-5,11-dihydro-13H-isoquino[3,2-b]quinazolin-13-one (9a). A mixture of compound 1a (1 g,
4.03 mmol) and anhydrous NaOAc (0.41 g, 5.1 mmol) in acetic anhydride was refluxed for 3 h, cooled, and held
at room temperature for 16 h. The precipitated product 9 was filtered off, washed with acetone, and
recrystallized from DMF.
5-Propionyl-5,11-dihydro-13H-isoquino[3,2-b]quinazolin-13-one (9b) was prepared by the method used
for product 9a using propionic anhydride (10 ml) in place of acetic anhydride and with NaHCO3 (0.42 g, 5.1 mmol).
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