5,8-isoquinolinediones. II. Chemical and electrochemical behavior of the 5,8-isoquinolinedione system

We have devised two general synthetic schemes to 5,8-isoquinolinediones and have investigated the chemical and electrochemical behavior of these compounds. The 1,4-addition reactions of these quinones with amines was shown to occur at the 7-position and a number of 7-amino-5,8-isoquinolinediones. were synthesized. The 1,4-addition of hydrogen bromide was also studied. The ethylenic double bond of the 5,8-quinone system underwent Diels-Alder additions to yield the oxidized forms of the adducts. The nucleophilic displacement of the methoxy group in 7-methoxy-5,8-isoquinoline was accomplished with both potassium hydroxide and morpholine. A Polarographic study of the half-wave potentials of substituted 5,8-isoquinolinediones showed a linear correlation between the change in the half-wave potential of the quinone system (ΔE° 1/2) resulting from the introduction of different substituents, and the substituent constants (σ_p-x).     

Sterol 5,8-endoperoxides

In this review the structures and properties of sterol 5,8-endoperoxides and methods for synthesizing them are discussed. Institute of Bioorganic Chemistry, Belarussian Academy of Sciences, 220141, Belarussia, Minsk, ul. Zhodinskaya, 5/2. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 599–619, September–October, 1998.     

Diels-Alder Reactions of 5,8-Ethano-5,8-dihydro-1,4-naphthoquinone with Cyclic Dienes

Diels-Alder cycloadditions of 1,3-cyclohexadiene and cyclopentadiene to π -facially dissymmetric 5,8-ethano-5,8-dihydro-1,4-naphtboquinone (1) were examined. The stereochemical outcome of the reactions, determined by a combination of chemical and spectral methods, indicates that addition of cyclic dienes to 1 occurs preferentially at the face syn to the etheno-bridge of 1. Cycloadducts 7a/7b and 8a/8b obtained from Diels-Alder reactions of 1 with cyclopentadiene and 1,3-cyclohexadiene undergo [2+2]-photocyclization to give caged compounds 9a/9b and 10a/10b , respectively. Stereoselective reduction of the enedione double bond in 7a/7b and 8a/8b with aqueous TiCl₃ in acetone affords cis-bis-bicyclic ring-fused 1,4-cyclo-hexadiones 11a/11b , and 12a/12b , respectively.     

Synthesis of 5-trifluoromethyl-5,8-dideazafolic acid and 5-trifluoromethyl-5,8-dideazaisofolic acid

The target folate analogue 5-trifluoromethyl-5,8-dideazafolic acid has been elaborated in a seven-step reaction sequence beginning with 2-fluoro-6-trifluoromethylbenzonitrile. The bridge-reversed isomer 5-trifluoromethyl-5,8-dideazaisofolic acid was prepared in six steps using the common intermediate 2,6-diamino-3,4-dihydro-4-oxo-5-trifluoromethylquinazoline. The key intermediate 2-amino-3,4-dihydro-4-oxo-5-trifluoromethyl-quinazoline was prepared using two distinct synthetic routes and the resulting products were found to be identical.     

Reactions of 5,8-dichloro-2,3-dicyanoquinoxaline with amines and hydrazines. A new and efficient synthetic approach to 3-amino-5,8-dichloroflavazoles

Reactions of 5,8-dichloro-2,3-dicyanoquinoxaline with primary amines and hydrazines under different experimental conditions were investigated. Alkylamines provided novel 3-alkylamino-5,8-dichloro-2-cyanoquinoxalines and N-alkyl-(5,8-dichloro-3-alkylamino-2-quinoxalinyl)carboxamidines in high yields. Alkylhydrazines and lithium arylhydrazinides gave previously unattainable 1-alkyl-3-amino-5,8-dichloroflavazoles and 3-amino-1-aryl-5,8-dichloroflavazoles in good to near quantitative yields whose molecular structure was confirmed by X-ray crystallography of 3-[N,N-bis(4-chlorobenzoyl)amino]-5,8-dichloro-1-phenylflavazole. Reaction with hydrazine gave 5,8-dichloro-3-hydrazino-2-quinoxalinylcarboxamidrazone quantitatively, which was converted to the parent compound of this class of flavazoles, 3-amino-5,8-dichloroflavazole, in high yield by a pyrolytic process involving loss of hydrazine.     

Quinones VIII. Synthesis of 3-t-butyl-5,8-dimethyl-1,10-anthraquinone

An 1,10-anthraquinone - stabilized only by alkylgroups - is prepared (in a four step synthesis) and described for the first time.     

Identifizierung von 5,8-Peroxid-Steroiden durch Gas-Chromatographie

Ohne Zusammenfassung     

2,6-Diamino-5,8-diaza-7,9-dicarba-purine

[reaction: see text] The title compound, a constitutional isomer of the natural nucleobase 2,6-diaminopurine, undergoes regioselective electrophilic substitutions at carbon C-9.     

Streptonigrin and related compounds. I. Some 2-phenyl- and 2,2-pyridylquinoline-5,8-diones

Methods for the synthesis of 6-amino-7-methoxy- and 7-amino-6-methoxy-2,2-pyridylquinoline- 5,8-diones and the corresponding 2-phenylquinoline-5,8-diones are described. The 6-aminoquinone system was generated by direct amination with sodium azide and the 7-aminoquinone system via the novel 6-hydroxy-7-nitroquinone intermediates. The basic skeleton was derived by the application of the Friedlander quinoline synthesis.