Electrochemical Synthesis of Keto and Enol Forms of Tetraketones of the Type 3,4-Diaroyl-2,5-hexanedione by Oxidative Dimerization of Aroylacetones

Tetraketones of the type 3,4-diaroyl-2,5-hexanedione: Ar = CsH;-, p-CHs-CsH4-, 3,4-(CHsh-CsHs-, p-CHaO-CsH4-, p- Cl-CsH4-, p-Br-C6H4- and 2-C4H3S- were prepared in good yield by oxidative anodic dimerization of aroylacetones. Electrochemical oxidation was carried out at constant current (4-5 A) in cylindrical cell without diaphragm with Pt-gauze anode and Ni-cathode. Depending on the method used (A or B) and depending on the properties of the electrolysed aroylacetones, dimer-products were isolated as stable keto or enol tautomers. Electrolysis in 80°/o aqueous methanol (Method A) gave keto or enol tautomers, while electrolysis in absolute methanol (Method B) yielded only enol tautomers

Electrochemical Reduction of Acetonylacetone in Hydrochloric Acid

The electrochemical reduction of acetonylacetone on a mercury cathode in aqueous hydrochloric acid medium has been studied. It has been shown that the electroactive species is the protonated form of acetonylacetone. The experimental results indicate -that the rate of electrochemical reduction is dependent upon the preceding chemical protonation step and/or adsorption of the electroactive species. The electrolysis at controlled potential (- 1.2 V vs. S. C. E .) yielded the following products : acetaldehyde; acetone, acetic acid, 2,5-hexanediol and 2,5-dimethyltetrahydrofuran. Possible mechanistic routes leading to the formation of these products are discussed

Synthesis of Amino Acids by Cathodic Cleavage of Phenylhydrazones of a-Keto Acids

Electrochemical synthesis of amino acids by reduction of phenylhydrazones of the folowing a-ketoacids: pyruvic, a-ketovaleric, a-ketoglutaric and a-ketooctane acid was studied. The corresponding a-amino acids were obtained in 44--55~/o yield using controlled potential electrolysis on mercury pool electrode in 0.5 M HCl aqueous ethanol solution. A mechanism rationalizing the reduction products of the phenylhydrazone of pyruvic acid as well as polarographic and coulometric data are proposed

Electrochemical Synthesis of Keto and Enol Forms of Tetraketones of the Type 3,4-Diaroyl-2,5-hexanedione by Oxidative Dimerization of Aroylacetones

Tetraketones of the type 3,4-diaroyl-2,5-hexanedione: Ar = CsH;-, p-CHs-CsH4-, 3,4-(CHsh-CsHs-, p-CHaO-CsH4-, p- Cl-CsH4-, p-Br-C6H4- and 2-C4H3S- were prepared in good yield by oxidative anodic dimerization of aroylacetones. Electrochemical oxidation was carried out at constant current (4-5 A) in cylindrical cell without diaphragm with Pt-gauze anode and Ni-cathode. Depending on the method used (A or B) and depending on the properties of the electrolysed aroylacetones, dimer-products were isolated as stable keto or enol tautomers. Electrolysis in 80°/o aqueous methanol (Method A) gave keto or enol tautomers, while electrolysis in absolute methanol (Method B) yielded only enol tautomers

Ferrocene Compounds. IX. Voltammetric Studies on the Oxidation of Some Ferrocene Derivatives

Oxidation potentials for ferrocene and a series of mono- (II- VII) and bridged diferrocenyl derivatives (VIII-XIV) have been determined by rotating disk electrode voltammetry and cyclic voltammetry using a platinum electrode in acetonitrile solution. The diffusion coefficients of monoferrocenyl derivatives, ranging from (0.74 to 2.38) X 10-5 cm2 s-1, were evaluated. Analysis of the\u27 results obtained for bridged diferrocenyl derivatives has shown that their oxidation potentials are sensitive to structural and electronic effects

Qualitative and Quantitative Aspects of Using Eshtblausalz B to Visualise 4-Hydroxycoumarin and Some of its Biologically Active Derivatives on Thin-Layer Chromatographs

Qualitative and quantitative aspects of the analysis of 4-hy..:. droxycoumarin and some of its biologically active derivatives (dicumarol, TromexanR, warfatin, 3-(co-bromoacetyl)-4-hydroxycoumarin and 3-(co-bromoacetyl)-4-hydroxy-7-bromocoumarin) were studied. The coumarin derivatives can be sharply separated by TLC on .silica gel HF254 using Eshtblausalz B for detection. Azo compounds of coumarine derivatives show that a linear relationship exists between spot-eluate absorbances and the amonts applied from 10 to 30 μg. The new rapid and sensitive method was obtained for qualitative and quantitative analysis of 4-hydroxy- . coumarin derivatives

Electrochemical Reduction of Intermediates in the Vitamin B6 Production. II. Reduction of 2-Methoxymethyl-3-nitro-4-methyl- 5-cyano-6-chloropyridine

2-Methoxymethyl-3-nitro-4-methyl-5-cyano-6-chloropyridine (I) was reduced on a mercury-pool in an electrolytic cell with a diaphragm. A mixture of acetic and hydrochloric acid was used as catholyte and diluted hydrochloric acid as anolyte. Compound I was reduced at - 0.5 V to 2-methoxymethyl-3-amino-4-methyl- 5-cyano-6-chloropyridine (II) (yield 67-820/o). Compound II was reduced at - 0.9 V to 2-methoxymethyl-3-amino-4-methyl-5- cyanopyridine (Ill) (yield 54-83-0/o). Compound III was reduced at -1.1 V to 2,4-dimethyl-3-amino-5-cyanopyridine (IV) (yield 48-660/o Compound IV was reduced at constant current density to 2,4-dimethyl-3-amino-5-aminomethylpyridine (V) (yield 82,40/o). Polarographic waves of I, II, and III are defined and character of limiting currents was determined according to the usual criteria

Electrochemical Reduction of Intermediates in the Vitamin B6 Production. II. Reduction of 2-Methoxymethyl-3-nitro-4-methyl- 5-cyano-6-chloropyridine

2-Methoxymethyl-3-nitro-4-methyl-5-cyano-6-chloropyridine (I) was reduced on a mercury-pool in an electrolytic cell with a diaphragm. A mixture of acetic and hydrochloric acid was used as catholyte and diluted hydrochloric acid as anolyte. Compound I was reduced at - 0.5 V to 2-methoxymethyl-3-amino-4-methyl- 5-cyano-6-chloropyridine (II) (yield 67-820/o). Compound II was reduced at - 0.9 V to 2-methoxymethyl-3-amino-4-methyl-5- cyanopyridine (Ill) (yield 54-83-0/o). Compound III was reduced at -1.1 V to 2,4-dimethyl-3-amino-5-cyanopyridine (IV) (yield 48-660/o Compound IV was reduced at constant current density to 2,4-dimethyl-3-amino-5-aminomethylpyridine (V) (yield 82,40/o). Polarographic waves of I, II, and III are defined and character of limiting currents was determined according to the usual criteria

Electrochemical Synthesis of Heterocyclic Compounds: X. Anodic Synthesis of s-Triazolo [3,4-a)pyridinium Salt Derivatives

A novel way of preparing s-triazolo[3,4-a] pyridinium salts by . anodic oxidation of aryl hydrazones of 2-acetylpyridine, 2-benzoylpyridine and 2-formylpyridine is described. Controlled potential electrolysis was carried out in CH3CN-Et4NX media using a Pt- electrode and a divided cell. The products were obtained in high yield (79-91°/o) and purity. It has been shown that the conformation of the starting hydrazone does not affect the yield of products and s-triazolo [3,4-a]pyridinium salts differing in anions can be prepared merely by using a supporting electrolyte carrying the desired anion (Clo4- , Tso-, BFn