Diphenyls, electroreduction

Rhodium and ruthenium complexes have also been studied as effective catalysts. Rh(diphos)2Cl [diphos = l,2-bis(diphenyl-phosphino)ethane] catalyzed the electroreduction of C02 in acetonitrile solution.146 Formate was produced at current efficiencies of ca. 20-40% in dry acetonitrile at ca. -1.5 V (versus Ag wire). It was suggested that acetonitrile itself was the source of the hydrogen atom and that formation of the hydride HRh(diphos)2 as an active intermediate was involved. Rh(bpy)3Cl3, which had been used as a catalyst for the two-electron reduction of NAD+ (nicotinamide adenine dinucleotide) to NADH by Wienkamp and Steckhan,147 has also acted as a catalyst for C02 reduction in aqueous solutions (0.1 M TEAP) at -1.1 V versus SCE using Hg, Pb, In, graphite, and n-Ti02 electrodes.148 Formate was the main... 

Electrochemical reduction of various 3,4-disubstituted-l,2,5-thiadiazole 1,1-dioxides (3,4-diphenyl- 10, phenanthro[9,10]- 51, and acenaphtho[l,2]- 53) gave the corresponding thiadiazoline 1,1-dioxides <1999CJC511>. Voltammetric and bulk electrolysis electroreduction of 3,4-diphenyl-l,2,5-thiadiazole 1-oxide 9 at ca. —1.5 V, in acetonitrile, gave 3,4-diphenyl-l,2,5-thiadiazole 8 (50%) and 2,4,6-triphenyl-l,3,5-triazine 54 (30%) (Equation 3) <2000TL3531>. 

The phenylhydrazone of acetone gave on hydrogenation over colloidal platinum a 90% yield of A(-isopropyl-A(-phenylhydrazine [950], and the semi-carbazone of benzil on electroreduction a 70% yield of A(-aminocarbonyl-N - 1,2-diphenyl-2-ketoethyl)hydrazine [95/]. 

Inokuchi, T. and Kusumoto, M. (2001) Selective dehalogenation of 6,6-dibromopenicillanates by indirect electroreduction with diphenyl diselenide as a recyclable mediator. J. Electroanal. Chem. 507, 34-36. 

Finally we cite the work of Grzeszczuk and Smith [117, 183] on the influence of solvents on the rate of electroreduction of several diphenyls in a limited number of solvents. In this case, disagreement of the kinetic data with the Marcus theory, but concordance with the dynamic model of the solvents, were observed. 

Maran [391] investigated electroreduction of optically active 2-bromo-7V-phenylpro-panamide giving optically active A -phenyl-2-hydroxypropanamide and cw-l,4-diphenyl-3,6-dimethyl-2,5-dioxopiperazine. 

---