Dienolate Anion Research Articles

Substituted naphthalenes and naphthols from benzynes and dienolate anions

A direct method for the preparation of substituted naphthalenes and naphthols from benzynes and dienolate anions is described. The naphthols are thus formed from conjugated esters and the naphthalenes from conjugated ketones. The scope and mechanism of the reaction have been briefly explored. Reaction between the dienolate anion from mesityl oxide and the benzyne from 2-(or 3-)bromoanisole produces 8-methoxy-1,3-dimethylnaphthalene in a regioselective manner.

ChemInform Abstract: SUBSTITUTED NAPHTHALENES FROM BENZYNES AND DIENOLATE ANIONS

A new, direct route to substituted naphthalenes and naphthols from benzynes and dienolate anions has been devised.

Substituted naphthalenes from benzynes and dienolate anions

A new, direct route to substituted naphthalenes and naphthols from benzynes and dienolate anions has been devised.

Methylation of kinetically generated dienolate anions derived from α,β-unsaturated ketones

Methylation of kinetically generated dienolate anions derived from α,β-unsaturated ketones

The copper‐catalysed oxidation of unsaturated carbonyl compounds: V. Kinetics and mechanism

AbstractWe have investigated the kinetics of the oxidation of α,β‐ and β,γ‐unsaturated aldehydes or ketones by oxygen in methanol containing a base and a cupric pyridine complex as a catalyst. The results show that the mechanism comprises the following steps: a rate‐determining deprotonation of the substrate, yielding a dienolate anion, oxidation of this anion by the cupric complex to a dienoxy radical (or to a charge transfer complex of cupric and the dienolate anion), and oxygenation of the radical resulting in a peroxy radical, which is reduced by a cuprous complex to a γ‐hydroperoxide anion. The subsequent base‐catalysed reactions of this species were discussed in Part III of this series.A cupric ion‐initiated chain oxidation of the substrate does not occur under the conditions applied. In the absence of oxygen the cupric complex yields a stoichiometric amount of the dienoxy radicals which combine to give α,α‐, γ,γ‐, α,γ‐ and oxygen‐γ‐dehydrodimers.The active cupric complex contains a methoxide group and only three pyridine molecules.

The copper‐catalysed oxidation of unsaturated carbonyl compounds: II. Base‐catalysed isomerization of isomesityl oxide and Δ5‐cholestenone

AbstractThe mechanism of the base‐catalysed isomerization of the βγ‐unsaturated ketones isomesityl oxide and Δ5‐cholestenone to their αβ‐unsaturated isomers was studied. The results are interpreted on the basis of a reaction scheme in which a dienolate anion, formed by deprotonation of the starting material, is an intermediate. The factors determining the rate of deprotonation of unsaturated ketones are discussed.Methoxide ions were found to deprotonate both ketones studied, whereas triethylamine, which deprotonates isomesityl oxide directly, was found to react with Δ5‐cholestenone only via the intermediate formation of methoxide ions from the solvent methanol.