Chemistry of Heterocyclic Compounds, Vol. 37, No. 6, 2001
PARTIALLY HYDROGENATED
AROMATIC SUBSTITUTED
a
TETRAZOLO[1,5- ]PYRIMIDINES
S. M. Desenko1, E. S. Gladkov1, S. A. Komykhov1, O. V. Shishkin2, and V. D. Orlov1
By treating 5-aminotetrazole with aromatic , -unsaturated ketones or with Mannich base
α β
hydrochlorides there have been synthesized aromatic substituted 4,7-dihydrotetrazolo[1,5-a]-
pyrimidines. They can be reduced to the corresponding 4,5,6,7-tetrahydro derivatives by the action of
NaBH4. The high thermodynamic stability of the 4,7-dihydrotetrazolo[1,5-a]pyrimidines when
compared with the 4,5-dihydro isomers has been revealed. Reaction of 5-aminotetrazole both with
cyclohexanone as well as with 2-cyclohexylidenecyclohexanone leads to formation of
9,9-pentamethylene-4,5,6,7,8,9-hexahydrotetrazolo[5,1-b]quinazoline, the structure of which was
demonstrated using X-ray crystallography.
Keywords:
5-aminotetrazole,
dihydrotetrazolo[1,5-a]pyrimidines,
, -unsaturated
α β
ketones,
tetrahydrotetrazolo[1,5-a]pyrimidines, molecular structure, rearrangement, cyclocondensation.
A convenient regioselective method for the synthesis of azolopyrimidines with a nodal nitrogen atom is
the cyclocondensation of aminoazoles with unsaturated ketones [1]. However, in the case of non-equivalently
substituted tetrazolo[1,5-a]pyrimidines, a solution to the question of the position of the substituent in the
pyrimidine ring demands consideration of not only the route of formation of the pyrimidine ring but also the
possibility of tetrazoloazide tautomeric conversions in the final compounds. The aim of our work is the
synthesis of partially hydrogenated aromatic substituted tetrazolo[1,5-a]pyrimidines and an investigation of their
possible mutual interactions via the open azide form.
The dihydro derivatives 3a-l were obtained by condensation of 5-aminotetrazole (1) with Mannich base
hydrochlorides 2a-c or with , -unsaturated ketones 2d-l. The reaction was performed by refluxing solutions of
α β
equimolar amounts of the starting materials in isoamyl alcohol (compounds 3a-e, 3 h) or in DMF (compounds
3f-l, 20-30 min). By the action of NaBH4 on a suspension of compounds 3d-g,i,j,l they could be reduced to the
tetrahydro derivatives 4 (Scheme 1). Compounds 3f,i,j,l have been reported by us previously [2]; the
characteristics of the compounds obtained for the first time 3a-e,g,h,k are given in Table 1.
It is known that the dihydro derivatives of azolopyrimidines can exist in the enamine (A) and the imine
(B) tautomeric forms [1]. The IR spectra of compounds 3a-e,g,h,k contain strong absorption bands for the
–NH–C=C– fragment in the region 1650-1690 cm-1 (Table 1), typical for 1,4-dihydropyrimidine derivatives, and
1
this points to an enamine structure (A) for these substances in the solid phase. The H NMR spectra of
compounds 3 contain signals for the protons of the NH group, the aromatic nuclei, the substituent, and the
__________________________________________________________________________________________
1
V. N. Karazin National University, Kharkov 61077, Ukraine; e-mail: desenko@univer.kharkov.ua,
2
e-mail: gladkov@isc.kharkov.com. NTK "Institute of Monocrystals", Kharkov 61001, Ukraine. Translated
from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 811-818, June, 2001. Original article submitted
September 27, 1999.
0009-3122/01/3706-0747$25.00©2001 Plenum Publishing Corporation
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