New possibilities of the functionalization of 6-hydrazino-1,3-dimethyluracils: one-pot synthesis of 5,7-dimethylpyrazolopyrimidine-4,6-dione and 1,3-dimethyl-5-arylidenebarbituric acid derivatives

3-aryl-5,7-dimethylpyrazolopyrimidine-4,6-diones and 5-benzylidene-1,3-dimethylpyrimidine-2,4,6-triones were obtained by heating hydrazones of 1,3-dimethyl-6 -hydrazinouraciles in trifluoroacetic acid (TFA). The same compounds were also obtained by heating the hydrazones of 1,3-dimethyl-6-hydrazinouraciles in aqueous ethanol in the presence of hydrochloric acid.3-aryl-5,7-dimethylpyrazolopyrimidine-4,6-diones and 5-benzylidene-1,3-dimethylpyrimidine-2,4,6-triones were obtained by heating hydrazones of 1,3-dimethyl-6 -hydrazinouraciles in trifluoroacetic acid (TFA). The same compounds were also obtained by heating the hydrazones of 1,3-dimethyl-6-hydrazinouraciles in aqueous ethanol in the presence of hydrochloric acid

New pathways for the synthesis of indolyl-containing quinazoline trifluoroacetohydrazides

Received: 19.08.2020. Accepted: 28.09.2020. Published: 07.10.2020.The reactions of indole-3‑carbaldehyde arylhydrazones with quinazoline in TFA proceed at the 7’ position of the aryl part of the hydrazone molecule to form σ-adducts of quinazoline trifluoroacetohydrazides.The authors are grateful to the Russian Foundation for Basic Research (grant 18‑33‑00727 mol_a) for financial support of the research

New opportunities for the synthesis of quinoxaline derivatives

Received: 21.01.2019. Accepted: 12.02.2019. Published: 29.03.2019.Convenient methods for the synthesis of quinoxaline derivatives with the use of nucleophilic aromatic substitution of hydrogen in heteroaromatic part of molecule in conditions of the acid catalysis were elaborated. The reactions of substitution of fluorine with amines in aromatic ring of 6,7-difluoroquinoxaline with the formation of monofluoro derivatives were studied.The research was supported by the Russian Foundation for Basic Research (grant: 18‑33‑00727 mol_a, grant: 18‑03‑00715 A) and the Russian Science Foundation (project 18‑13‑00161)

A simple means of preparing quinoxaline derivatives: Direct introduction of C-nucleophiles into the quinoxaline nucleus by substituting a hydrogen atom

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. © 2013 Springer Science+Business Media New York

Synthesis, thermal transformations, and mass spectrometric fragmentation of 4,4'-[1,2-bis(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)ethane-1,2-diyl]- bis(5-methyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one)

Quinoxaline reacted with 3-methyl-1-phenylpyrazol-5-one at room temperature in the presence of triethylamine in DMSO solution, to form 4,4'-[1,2-bis(5- hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)-ethane-1,2-diyl]bis(5-methyl-2- phenyl-1,2-dihydro-3H-pyrazol-3-one). Heating of the obtained crystalline product at 240-250 C temperature led to the known 4-[(5-hydroxy-3-methyl-1- phenyl-1H-pyrazol-4-yl)methylidene]-5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3- one. The mass spectral fragmentation of the obtained compounds was characterized. © 2013 Springer Science+Business Media New York