Electrochemical Synthesis of Heterocyclic Compounds. XI. Annelation of Coumarin Ring via Cathodic Reduction of 3-Nitrocoumarin Derivatives

Annelation of the coumarin ring was performed via cathodic reduction of 3-nitrocoumarin derivatives (1-4) by controlled potential. The reduction of 3-nitro-4-aminocoumarin, 1, gave 3,4-diaminocoumaDin, 5, and subsequent treatment with formic acid furnished tlie novel 4H [1] benzopyrano [3,4-b] imidazole-4-on ring system 6. The condensation of 5 with trifluoracetic acid anhydride, acetic acid anhydride, and benzil gave products 7, 8 and 9, respectively. The reduction of 3-nitro-4-carbetoxymethylthiocoumar.in, 2, gave the cyclic product 3H, 5H [1] benzopyrano[3,4-b]l,4-thiazine (2H)-3,5-dion, 10. The r.eduction of 3-nitro-4-(2-formylphenoxy)coumarin, 3, and subsequent intramolecular condensation of amino derivative 11 gave the novel SH [1] benzopyrano[3,4-b]l,4-benzoxazepin- 8-on ring system 13. The same compound 13 was obtained through reduction of 3-ruitro-4-chlorcoumarin, 4, to 3-amino-4- -chlorocoumarin, 12, acid and subsequent ·condensation of 12 with salicylaldehyde

Electrochemical Synthesis of Heterocyclic Compounds. XI. Annelation of Coumarin Ring via Cathodic Reduction of 3-Nitrocoumarin Derivatives

Annelation of the coumarin ring was performed via cathodic reduction of 3-nitrocoumarin derivatives (1-4) by controlled potential. The reduction of 3-nitro-4-aminocoumarin, 1, gave 3,4-diaminocoumaDin, 5, and subsequent treatment with formic acid furnished tlie novel 4H [1] benzopyrano [3,4-b] imidazole-4-on ring system 6. The condensation of 5 with trifluoracetic acid anhydride, acetic acid anhydride, and benzil gave products 7, 8 and 9, respectively. The reduction of 3-nitro-4-carbetoxymethylthiocoumar.in, 2, gave the cyclic product 3H, 5H [1] benzopyrano[3,4-b]l,4-thiazine (2H)-3,5-dion, 10. The r.eduction of 3-nitro-4-(2-formylphenoxy)coumarin, 3, and subsequent intramolecular condensation of amino derivative 11 gave the novel SH [1] benzopyrano[3,4-b]l,4-benzoxazepin- 8-on ring system 13. The same compound 13 was obtained through reduction of 3-ruitro-4-chlorcoumarin, 4, to 3-amino-4- -chlorocoumarin, 12, acid and subsequent ·condensation of 12 with salicylaldehyde

Chemistry of Coumarins. Some Novel Heterocycles from Deoxygenation of 4-Arylamino-3-nitrocoumarins

Reaction of 4-arylamino-3-nitrocoumarins with triethyl phosphite was investigated. The yet unreported 6-H-1-benzopyrano- -[4,3-b]quinoxalin-6-one (2a) system was synthesized and characte- rized on the basis of spectral and analytical data. Four derivatives (2a-2d) were obtained in good yields ranging from 68 to 76

Electrochemical Synthesis of Heterocyclic Compounds. Part 21.1 Anodic Oxidation of 1-Arylmethylenesemicarbazides in Methanol

Anodic oxidation of 1-arylmethylenesemicarbazides (1-5) was performed in methanol-tetraethylammonium perchlorate electrolyte solution by constant-current electrolysis. As a result of anodic oxidation, the corresponding oxadizoles (la-3a) were isolated in good yields, ranging from 51 to 65%. The anodic oxidation represents a novel efficient conversion of an aromatic aldehyde to an aromatic methyl ester (3b-5b) through oxidation of its semicarbazones

Electrochemical Synthesis of Heterocyclic Compounds. Part 21.1 Anodic Oxidation of 1-Arylmethylenesemicarbazides in Methanol

Anodic oxidation of 1-arylmethylenesemicarbazides (1-5) was performed in methanol-tetraethylammonium perchlorate electrolyte solution by constant-current electrolysis. As a result of anodic oxidation, the corresponding oxadizoles (la-3a) were isolated in good yields, ranging from 51 to 65%. The anodic oxidation represents a novel efficient conversion of an aromatic aldehyde to an aromatic methyl ester (3b-5b) through oxidation of its semicarbazones

The Avarol-Avarone Redox Behaviour in Acetonitrile

The oxidation of avarol and the reduction of avarone were studied at a Pt electrode in acetonitrile-tetraethyl-ammonium perchlorate media. The oxidation of avarol in acetonitrile takes place by formation of a two electron oxidation product, presumably the »protonated avarone«. The reduction of avarone takes place in two steps by formation of the stable radical anion which is reduced to the dianion at amore negative potential