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LIPSON et al.
with benzaldehyde, and the other involves possible
formation of enaminoketone by condensation of amine I
with diketone VII.Analogous processes were postulated
in reactions of dimedone with aromatic amines [13].
dimethylformamide is involved in the process, and the
mode of pyrimidine ring closure changes. Probably, the
mechanism of these reaction includes formation of
intermediate A which undergoes cyclization to triazolo-
[2,3-a]quinazolin-6-one with participation of DMF
molecule.
In order to verify the possibility for the three-
component condensation to occur via successive reac-
tions of diaminotriazole I with benzaldehyde II, III, or
VI and dimedone, we examined the reaction of the latter
with Schiff bases XVIIIXX. Compounds XVIIIXX
(Tables 1, 2) were synthesized by heating equimolar
amounts of the corresponding aldehyde with aminoazole
I in boiling alcohol and were brought into reaction with
dimedone in DMF. As a result, we isolated only
triazoloquinazolinones VIII, IX, XII. No alternative
products like XIII were detected. Therefore, Schiff bases
XVIIIXX act in this reaction as synthetic equivalents
of aldehydes.
EXPERIMENTAL
The IR spectra were recorded on a Specord M-82
spectrometer from samples prepared as KBr pellets. The
1H NMR spectra were obtained on a Varian 200
instrument from solutions in DMSO-d6 using TMS as
internal reference. The mass spectra were recorded on
an MSBC SELMI spectrometer with a 10 mCi252Cf
source for positive and negative ions (accelerating voltage
±20 kV). The reaction mixtures and products were
analyzed by TLC on Silufol UV-254 plates using CHCl3
MeOH (9 : 1) as eluent. The melting points were
determined on a Kofler device.
Enaminoketone XXI was obtained by heating a mix-
ture of dimedone and amine I in DMSO. Its struc-
ture was determined on the basis of the spectral data
(Tables 1, 2). According to the mass spectrum, the
molecular weight of XXI is 221, i.e., the reaction of I
with dimedone is accompanied by liberation of water
2-Arylmethylene-5,5-dimethylcyclohexane-1,3-diones
XIV and XV were synthesized by the procedure reported
in [11]. The procedure for preparation of xanthenediones
XVI and XVII and their properties were described in
[12].
1
molecule. The H NMR spectrum of compound XXI
2-Amino-5-aryl-8,8-dimethyl-5,6,7,8,9,10-hexa-
hydro[1,2,4]triazolo[3,2-b]quinazolin-6-ones VIII
XII (general procedure). a. A mixture of 1 mmol of
3,5-diamino-1,2,4-triazole (I), 1 mmol of dimedone (VII),
and 1 mmol of aldehyde IIVI in 1 ml of DMF was heated
for 10 min under reflux until a solid material began to
separate from the mixture. The mixture was cooled, 5 ml
of 2-propanol was added, and the precipitate was filtered
off and recrystallized from DMF2-propanol (1 : 2). Mass
spectrum of VIII: m/z 310/308 [M + H]/ [M H].
(Table 2) contains signals from amino, methyl, and
methylene groups and singlets due to two NH protons
and CH proton in the enone fragment. These data support
structure XXI. Enaminoketone XXI was heated with
benzaldehyde II in DMF in the absence of a catalyst
and in the presence of a catalytic amount of hydrochloric
acid. Triazoloquinazolinone VIII was obtained only in the
presence of hydrochloric acid.According to the TLC data
(CHCl3MeOH, 9:1), under these conditions compound
XXI decomposes to initial amine I and dimedone (VII).
On prolonged heating in the absence of an aromatic
aldehyde, reaction (7) involves DMF as carbonyl
component, and quinazolinone XXIII is formed. If
benzaldehyde (II) is present in the reaction mixture, it
reacts with dimedone to form arylmethylene derivative
XIV or xanthenedione XVI. In the next stage, the latter
reacts with diaminotriazole I, following one of the above
mechanisms. Thus the formation of compounds VIIIXII
through intermediate enaminoketone XXI [reaction (1)]
seems to be improbable.
b. A mixture of 1 mmol of amine I and 1 mmol of
2-arylmethylene-5,5-dimethylcyclohexane-1,3-dione XIV
or XV in 1 ml of DMF was heated for 10 min until a solid
material began to separate from the mixture. Products
VIII and IX were isolated as described above. Yield of
quinazolines VIII and IX 55 and 63%, respectively.
c. A mixture of 1 mmol of amine I and 1 mmol of 9-
aryl-3,3,6,6-tetramethyl-3,4,5,6,7,9-hexahydroxanthene-
1,8(2H)-dione XVI and XVII in 1 ml of DMF was heated
for 10 min under reflux. Products VIII and IX were
isolated as described above. Yield of quinazolines VIII
and IX 51 and 56%, respectively. Dimedone (VII) was
extracted from the filtrate with chloroform. The solvent
was removed, and the oily residue was crystallized from
methanol to isolate diketone VII with mp 150151°C;
published data [14]: mp 148150°C.
Our experimental data give us grounds to believe that
arylmethylene derivatives of dimedone and xanthen diones
are the key intermediates in the three-component
condensation leading to the triazolo[3,2-b]quinazolin-6-
one system. In the absence of an aromatic aldehyde,
RUSSIAN JOURNALOF ORGANIC CHEMISTRY Vol. 41 No. 1 2005
Lipson
