Fructuoso Barba

Electrochemical obtention of cis- and trans-3,6-dimethoxy-3,6-dimethyl-1,4-cyclohexadienes

Preparation par oxydation sur electrode de graphite du p-xylene dans le melange methanol-methanolate de sodium

Indirect electrochemical oxidation of cyclic ketones: Influence of ring size, mediator and supporting electrolyte on the result of the reaction

Abstract The result of the indirect electrochemical oxidation of cyclic ketones in methanol in an undivided cell in the presence of sodium halides depends on the ring size of ketone and the type of mediator. Selectivity of the reaction in some cases and current efficiency are increased by addition of supporting electrolyte - sodium hydroxide. Formation of cyclic 2,2-dimethoxycycloalkanols and the electrochemically induced Favorskii rearrangement with the formation of methyl cycloalkencarboxylates containing in the ring one carbon atom less than starting ketone are the main ways of the indirect electrochemical oxidation of cyclic ketones.

Electrosynthesis of 3-chloro-4-substituted-coumarins

A facile synthesis of 3-chloro-4-substituted-coumarins (2) was performed in good yield by cathodic reduction of 2-acyl(or aroyl)phenyltrichloroacetates (1). When 2-acetylphenyldichloroacetate (3) was employed, a mixture of 3-chloro-4-methyl-coumarin (2a) and 4-methyl-coumarin (4) was obtained. The cleavage of the ester was the main reaction when 2-acetylphenylchloroacetate was reduced.

Indirect electrochemical oxidation of aliphatic ketones mediated by the NaI–NaOH system:a facile way to unsaturated conjugated esters

Abstract Indirect electrochemical oxidation of aliphatic ketones in methanol in an undivided cell in the presence of sodium iodide–sodium hydroxide system leads to the corresponding unsaturated esters as a result of the electrochemically induced Favorskii rearrangement of the primarily formed α , α -diiodoketones.

Indirect electrochemical oxidation of cyclic ketones: Strong influence of ring size on the result of the reaction

Abstract The result of the indirect electrochemical oxidation of cyclic ketones in methanol in the undivided cell in the presence of sodium iodide depends on the ring size. Cyclopentanone affords 2,2-dimethoxycyclopentanone. While cyclohexanone gives rise 2,2-dimethoxycyclo-hexanol, and cyclic ketones with higher ring size undergo new type of the electrochemically induced Favorskii rearrangement with the formation of methyl cycloalkencarboxylates containing in the ring on the one carbon atom less than starting ketone. So the simple electrocatalytic system can distinguish the ring size of cyclic ketones.

Electrochemical synthesis of 3-phenylcinnamonitrile by reduction of benzophenone in acetonitrile

Abstract The electrochemical cyanomethylation of benzophenone in acetonitrile was investigated as an interesting way of synthesizing high yield of 3-phenylcinnamonitrile (55% for 50% of theoretical circulated charge). This synthetic method uses the benzophenone radical-anion as a strong electrogenerated base to abstract a proton from the solvent and obtain the nucleophile − CH 2 CN. This anion is capable of yielding cyanomethylated products very easily. In our case the reaction of this anion with benzophenone yields 3-phenylcinnamonitrile in a father–son like mechanism.

Electrosynthesis of 2-benzhydrylidene-4,4-diphenyl-[1,3]oxathiolan-5-one: The reaction pathway.

Abstract The pathway for the electrochemical formation of 2-benzhydrylidene-4,4-diphenyl-[1,3]oxathiolan-5-one ( 2 ), in dichloromethane tetraethylammonium bromide on graphite cathode is proposed. It involves reaction between electrogenerated diphenylketene ( 3 ), 2-bromo-2,2-diphenylacetyl bromide ( 1 ) and sulfide anion. The latter is formed from H 2 S generated in the anodic compartment and electrogenerated bases.

A new proposed mechanism for the cathodic reduction of a carbon–chlorine bond in 2-acetylphenyltrichloroacetate

Abstract The cathodic reduction of 2-acetylphenyltrichloroacetate at a controlled potential of −0.5 V (vs SCE) yields 3,3-dichloro-4-hydroxy-4-methyl-3,4-dihydrocoumarin. The charge consumption is 1e−/substrate molecule, which is in agreement with a non-conventional R–X→R−+X mechanism.

A new carbene route for the electrochemical reduction of phenacyl bromide

In previous papers we have reported the cathodic reduction of phenacyl bromides in aprotic media, yielding 2,4-diary1 furans [l]. The process is shown in scheme 1 (pathway a). When the reaction is carried out with very slow addition of I to the solution, the product obtained is the (E)-4-bromo-l,3-diphenyl-2,3-epoxy-butan-l-one (VI) 123 (pathway b). In this paper we report the cathodic reduction of phenacyl bromide when it is added slowly to a solution containing an aprotic solvent and various substances, such as ethyl bromoacetate or bencylidenaniline, which would be expected to react as electrophiles towards the nucleophile generated. However, rather than the expected products truns-1,2,3-tribenzoyl cyclopropan (11, 2-(3H)_3,5-diphenyl furanone (2) and acetophenone were obtained (pathway c). Several methods of obtaining products 1 and 2 have been reported in the literature. A procedure [3,4] involving the treatment of phenacyl bromide with bases has been reported to yield 1 but 2 is not obtained. However, both 1 and 2 can be obtained by decomposition of diazoketones, which is caused by thermal, photochemical or catalytic processes. These reactions are well known to proceed via a carbene intermediate which both trimerizes to 1 and undergoes Wolff rearrangement to a ketene which reacts with a diazoketone molecule leading to 2 [5-71. We wish to demonstrate here that our electrochemical process also involves a carbene intermediate. The high dilution created by the slow addition of I produces a suitable medium in which anion II diffuses from the electrode surface so that it can react as a base towards a new molecule of I, generating acetophenone and the

One-Pot Formation of 1,3,4-Oxadiazol-2(3H)-ones and Dibenzo[c,e]azepines by Concomitant Cathodic Reduction of Diazonium Salts and Phenanthrenequinones

The one-pot concomitant electrochemical reduction of phenanthrenequinones (1, 2) and arenediazonium salts (3a-f) led to the formation of 1,3,4-oxadiazol-2(3H)-ones (4a-f, 5a) and dibenzo[c,e]azepines (6a-f) when N-methylformamide was used as the solvent. A new pathway, different from those previously described with other aprotic solvents, is proposed. The experimental data support a radical mechanism for the electrochemical process followed by an internal rearrangement to give the products.