Colin William Greenhalgh

The synthesis of quinodimethanes in the benzodifuranone and benzodipyrrolidone series

Abstract The condensation of hydroquinone and 2,5-substituted hydroquinones with mandelic acids, or of 1,4-benzoquinone and 2,5-substituted 1,4-benzoquinones with mandelic acids or arylacetic acids gives 3,7-diaryl-2,6-dioxo-2,6-dihydrobenzo[1,2-b:4,5-b′]difuran derivatives. Analogous benzodipyrrolidones have been obtained from 1,4-phenylenediamine and N,N′-dimethyl-1,4-phenylenediamine. Both series are novel chromogens and have application as dyestuffs. The red compound obtained from 1,4-benzoquinone and cyanoacetic acid and reported to be a lin-pentacenetriquinone has been shown to be 3,7-bis(4-hydroxyphenyl)2,6-dioxo-2,6-dihydrobenzo[1,2-b:4,5-b′]difuran.

Naphthoquinone mono- and di-methide lactones

Monolactones which are derivatives of 7-hydroxynaphtho[1,8-bc]pyran-2,6-dione are obtained by reaction of simple juglones with ethyl chloroformylacetate, and by condensation of mandelic acid with 2,6-dibromo-1,5-dihydroxynaphthalene. Dilactones are formed by condensation of mandelic acid with 1,5-dihydroxynaphthalene, which yields 3,8-diphenylnaphtho[1,2-b : 5,6-b′]difuran-2,7-dione and/or 3,8-diphenylnaphtho[1,8-bc : 4,5-b′c′]dipyran-2,7-dione; with 2,3-dihydroxynaphthalene it gives 3,8-diphenylnaphtho[2,1-b: 3,4-b′]difuran-2,9-dione.

The stabilities of Meisenheimer complexes. Part 40. A kinetic study of the reaction of 1-chloro-2,4-dinitrobenzene with sulphite ions in water–dimethyl sulphoxide mixtures

Kinetic and equilibrium data are reported for the reactions of 1-chloro-2,4-dinitrobenzene with sulphite ions in dimethyl sulphoxide–water mixtures. Attack at the unsubstituted 5-position yields an observable σ-adduct and is shown to be more rapid by a factor of ca. 12 than attack at the 1-position. The latter process which yields the substitution product is likely to involve intermolecular attack of sulphite on the substrate rather than intramolecular re-arrangement of the 5-adduct.

The stabilities of Meisenheimer complexes. Part 42. Kinetic studies of the reactions of methyl 3,5-dinitrobenzoate and of methyl 4-chloro-3,5-dinitrobenzoate with hydroxide ions in dimethyl sulphoxide–water mixtures. Competitive nucleophilic attack at aryl and carbonyl carbon atoms

Kinetic and equilibrium data, obtained by stopped-flow spectrophotometry, are reported for the reactions of methyl 3,5-dinitrobenzoate (1) and methyl 4-chloro-3,5-dinitrobenzoate (5) with hydroxide ions in dimethyl sulphoxide–water mixtures. There is evidence for competition between attack at carbonyl and aryl carbon atoms, the latter becoming relatively favoured as the proportion of dimethyl sulphoxide in the solvent is increased. It is shown that the major pathway in the formation of 4-hydroxy-3,5-dinitrobenzoate from (5) involves hydroxide attack at the carbonyl function followed by slow attack at the ring carbon atom carrying chlorine.

Reactions of 1-X-2,4,6-trinitrobenzenes and 1-X-2,4-dinitrobenzenes with hydroxide ions. Comparison of the relative rates of nucleophilic attack at substituted and unsubstituted ring-positions

Kinetic and equilibrium measurements are reported for the reactions with hydroxide ions of 1-X-2,4,6-trinitrobenzenes (X = H, F, Cl, Br, I) in water and of 1-X-2,4-dinitrobenzenes in dimethyl sulphoxide–water (80:20, v/v). Attack at unsubstituted ring-positions results in the formation of σ-adducts while attack at halogen-substituted positions leads to 2,4,6-trinitro- or 2,4-dinitro-phenolate ions by nucleophilic substitution; the rate constants for these processes are compared. The results provide evidence for two types of steric effects: (i) increasing the size of the halogen atom results in disruption of the planarity of the nitro-groups, giving a general decrease in reactivity at both unsubstituted and halogen-substituted positions; (ii) unfavourable steric and electrostatic repulsion between entering and leaving groups slows the attack of hydroxide at carbon atoms carrying Cl, Br, or I. In water there is evidence for ionization of added hydroxy groups [Scheme 1; (2)⇌(3)] and for nucleophilic displacement of nitrite by hydroxide within the 3-hydroxy adducts (2) and (3). Contrary to a recent report the reaction of hydroxide ions with nitro compounds to form hydroxy adducts is found to occur without the observation of spectrophotometrically detectable intermediates.