STUDY OF THE CONDENSATION OF ETHYL 5-METHYL-1,2,4- TRIAZOLO[1,5-a]PYRIMIDIN-7-YL)ACETATE WITH ALLYL BROMIDE, DMF-DEA AND DI(2-CHLOROETHYL)AMINE HYDROCHLORIDE

Abstract

Ethyl 5-methyl(1,2,4-triazolo[1,5-a]pyrimidin-7-yl)acetate : 1 has been used as
a precursor for the synthesis of 1,2,4-triazolo[1,5-a]pyrimidine derivatives.
Thus, the action of an excess of allyl bromide under liquid-solid phase transfer
catalysis (PTC) conditions leads to ethyl 2-(5-methyl-(1,2,4-triazolo
[1,5-a]pyrimidin-7-yl)-pent-4-enoate : 2 and ethyl 2-(prop-2-en-3-yl)-2-(5-
methyl-(1,2,4-triazolo[1,5-a]pyrimidin-7-yl)-pent-4-enoate : 3
Moreover, the condensation of compound 1 with N,N-dimethylformamidediethylacetal at reflux affords ethyl (2E)-3-dimethylamino-2-(5-methyl-1,2,4-
triazolo[1,5-a]pyrimidin-7-yl)prop-2-enoate 4. Also 5-methyl-1,2,4-triazolo[1,5-
a]pyrimidine 5 has been obtained during the condensation of compound 1 with
di(2-chloroethyl)amine hydrochloride at reflux of DMF in the presence of
potassium carbonate.
A plausible mechanism has been proposed to explain the formation of
triazolo[1,5-a]pyrimidine 5 involving an oxidation reaction of the methylene
group of the side-chain in position 7 of the biheterocyclic compound.
The structures of all compounds obtained have been elucidated on the basis of
NMR spectroscopy and confirmed by a single-crystal X-ray diffraction analysis.