Isidoro 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

Reactivity of 3,6-dimethoxy-3, 6-dimethylcyclohexa-1, 4-diene: nuclear versus benzylic nucleophilic substitution

Abstract The treatment of cis / trans -3,6-dimethoxy-3,6-dimethylcyclo-hexa-1, 4-diene ( ca . 1/1 mixture; easily prepared electrochemically in multigram scale from p -xylene) under acidic conditions (acetic, trifluoroacetic, sulfuric, or a Lewis acid) yields almost exclusively 2-methoxy-1,4-dimethylbenzene 4, through a transposition reaction. The use of aqueous hydrochloric or hydrofluoric acid gives 2,5-di-methylphenol 12, and with hydrogen chloride a mixture of 2- and α- chloro- P -xylene (13, 14) is isolated. Different oxygen-, nitrogen-, and sulfur-containing nucleophiles (alcohols, thiols, or hydrazoic acid) react with 3 under acid catalysis giving the corresponding products resulting from a nuclear or/and benzylic substitution on P -xylene (15-20). The reaction of compound 3 with organolithium reagents affords exclusively benzylic products 21 in a regiospecific manner. In all cases the mixtures of isomers are separated by column chromatography. The lithiation of compound 3 with lithium powder or lithium naphthalenide fails, giving P -xylene. A probable mechanism is proposed for the studied reactions.

Anodic oxidation of methylnaphthalenes and 9-methylanthracene

Abstract Anodic methoxylation of a series of methylnaphthalenes (1-methylnaphthalene, 2-methylnaphthalene, 1,3-dimethylnaphthalene, 1,4-dimethylnaphthalene, 1,5-dimethylnaphthalene, 2,6-dimethylnaphthalene, 2,3,5-trimethylnaphthalene) and 9-methylanthracene afforded a series of nuclear-addition products. The process of nuclear addition is only observed in an aromatic ring and no chain methoxylated products were obtained. A probable mechanism is provided.

Anodic oxidation of alkylated biphenyls. Synthetic routes to certain cyclohexa-1,4-dienes

Abstract The anodic methoxylation of 3-phenyltoluene, 4-phenyltoluene and 4,4′-dimethylbiphenyl carried out under constant current intensity afforded a number of new cyclohexa-1,4-dienes.