Kaliendina S., Brynzei M., Kut M., Sukharev S.M., Ostapchuk Е., Onysko M. REGIOSELECTIVITY OF ALKYLATION OF 2-(THIOPHENE-2-IL)THIENO[2,3 d]PYRIMIDINE-4(3H)-ONE

Thieno[2,3-d]pyrimidines are an important class of heterocyclic compounds with a wide range of biological activities. The thieno[2,3-d]pyrimidin-4-one system is of the greatest interest to scientists, as it is one of a large number of possible thienopyrimidine derivatives. The presence of an amide fragment in these molecules allows for the introduction of various substituents via alkylation reactions. On the other hand, the presence of N- and O-nucleophilic centres makes it possible to form different types of alkylation products. In the present work, the alkylation reaction of 5,6-dimethyl-2-(thiophen-2-yl)thieno[2,3-d]pyrimidin-4(3H)-one, which contains N(3)- and O-nucleophilic centres for attacking alkylating reagents, was investigated. Allyl bromide was used as an alkylating reagent. It was found that the alkylation of 5,6-dimethyl-2-(thiophen-2-yl)thieno[2,3-d]pyrimidin-4(3H)-one with allyl bromide in DMF resulted in the regioselective preparation of 4-(allyloxy)-5,6-dimethyl-2-(thiophen-2-yl)thieno[2,3-d]pyrimidine, which can be used in the future to study the process of electrophilic intramolecular cyclisation. An increase in the reaction time of the starting reagents leads to an increase in the yield of the target ester. Keywords: 5,6-dimethyl-2-(thiophen-2-yl)thieno[2,3-d]pyrimidin-4(3H)-one; alkylation; regioselectivity; ether; 4-allyloxypyrimidine.