A. Ivachtchenko, S. Kovalenko, O. G. Drushlyak
2002
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0
Influential Citations
2
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Journal
Heterocyclic Communications
Abstract
New benzimidazo[ 1,2-c]quinazoline-6(5//)-thiones were prepared by cyclization of 3-(2aminophenyl)quinazoline-2-thioxo-4-ones. Alkylation of these products led to S-alkyl derivatives of benzimidazo[ 1,2-c]quinazolines. Quinazolinethione derivatives and some polycondensed heterocycles comprising a fragment of quinazolinethione are of interest as biologically active substances. For instance, methyl 6-oxo3,4-dihydro-2//,6//-[ 1,3]thiazino[2,3-6]quinazoline-2-carboxylate possesses antihypertensive activity, 2-benzylthio-3-[2-[4-(2-methoxyphenyl)piperazino]ethyl]-4(3//)-quinazolinone is an effective alpha 1-adrenoceptor antagonist and shows an antihypertensive effect, iV-[4-(l//-imidazoll-yl)butyl]-7-isopropyl-5-oxo-5//-thiazolo[2,3-6]quinazoline-2-carboxamide is a leukotriene antagonist mediator release inhibitor and exhibits an antiallergic and antiasthmatic effect. To expand the search range for potential drug precursors we made an attempt to combine them with a fused benzimidazole system. The benzimidazole was expected to be formed by cyclization of 3-(2-aminophenyl)quinazolin-4-on-2-thiones 3, 4 obtained by us in an almost 100% yield by condensation of 2-carboxymethylphenylisothiocyanates 1, 2 with o-phenylenediamine (Scheme). Cyclizations of compounds 3, 4 were carried out in a mixture of 80% N,Ndimethylformamide and 20% acetic acid under reflux for 3 hours. Quite unexpectedly, instead of the anticipated benzimidazo[l,2-£]quinazoline-4(l//)-ones 5, 6, benzimidazo[l,2-c]quinazoline6(5//)-thiones 7, 8 were obtained in high yield (Table). The structure of the synthesized compounds has been validated by MS and 'H NMR. There is a strong signal for a molecular ion at m/z 251 and m/z 309 in the mass spectra of compounds 7 and 8, respectively. The diagnostic peak for S at