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Unsubstituted quinoxaline (I) reacts with dimedone, indanedione, and 1-phenyl-3-methylpyrazol-5-one in dimethylsulfoxide in the presence of acid to form monosubstitution products II -IV. Quinoxaline reacts with 1,3-dimethylbarbituric acid in dimethylsulfoxide solution at room temperature to form monosubstitution product V without external catalysis. Heating of I with resorcinol in ethanol in the presence of acid produced resorcinol derivative VI. In the presence of base, quinoxaline reacts with 1-phenyl-3-methylpyrazol-5-one to form dipyrazolylmethane VII and tetrapyrazolylethane derivative VIII. Compound VIII undergoes cleavage to form dipyrazolylmethane VII in dimethylformamide solution with boiling or in the presence of iodine at room temperature.

ChemInform Abstract Reaction of antibiotic 2-methylfervenulone (MSD-92) (I) with nucleophiles is investigated. In each case (acid and base catalysis), the 4,4a-addition product is obtained. 4-Substituted o-phenylenediamines do not give the analogous addition reaction, but the alcohol used as the solvent reacts instead. The products have low antimicrobial activity.

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We have studied the reactions of alkylation, oxidation, and hydrolysis of 3-aryl-2-thioxoquinazolin-4-ones. Alkylation in an alkaline medium occurs exclusively at the sulfur atom. Oxidation by hydrogen peroxide leads to formation of 3-arylquinazoline-2,4-diones. The latter are also obtained in base or acid hydrolysis of the synthesized S-alkyl derivatives. When 3-aryl-2-thioxoquinazolin-4-ones are reacted with iodine, we obtain the disulfides, while the reaction with chlorine in hydrochloric acid leads to 2chloroquinazolin-4-ones. Studying the mass spectrometric behavior of the compounds obtained made it possible to observe in the gas phase ring-chain isomerization of the heterocyclic ring, and also S-N migration of the propargyl radical in molecular ions of the S-propargyl derivatives.