Thieno [2, 3-d] Pyrimidine-4-Ones. Part 4.* Directions of Reactions of the 2-Oxo-, -Thioxo-5, 6-Dimethyl-3, 4-Dihydrothieno [2, 3-d] Pyrimidine-4-Ones with Electrophilic Reagents

Interaction of 5,6-dimethyl-3,4-dihydrothieno[2,3-d]pyrimidine-4-one (1), -thione(2) with alkylation agents (methyl-, ethyl-, n-propyl-, n-butyl iodides, allylbromide, benzyl chloride) in different conditions (in the presence of catalyst and/or without catalyst) were investigated. It was shown that methyl group in position 5 under action of nitrating mixture (NM) takes place aromatic ipso-substitution reaction or its oxidation up to corresponding carboxylic acid. Directions of reactions depend on nature of substituent in position N-3. It is revealed, that at absence of the substituent in position 3 (compounds 1, 2, 11) the electrophilic ipso-substitution of methyl group by nitro group with formation of 5-nitroderivatives took place. It is found, that at interaction of compounds 3, 19 with NM instead of substitution of methyl groups at C-5 go in an expected direction, i.e. there are oxidation of methyl groups.