Reactions of carbonyl compounds in basic solutions. Part 23.1 The mechanism of the base-catalysed ring fission of 2,2-dihydroxyindane-1,3-diones

Abstract

The base-catalysed ring fission of a series of substituted 2,2-dihydroxyindane-1,3-diones and phenalene-1,3-dione has been studied in 30% (v/v) dioxane-water. The reaction proceeds in two distinct steps. The first is a relatively fast base-catalysed ring fission to give substituted o-carboxyphenylglyoxals, and the second is a rearrangement of the latter resulting in formation of substituted o-carboxymandelic acids. Rate coefficients for the ring fission of a limited series of substrates have been determined at 25.0 ЊC. The reaction is first order in the mono-anion of the substrate alone. The Hammett reaction constants, , have been obtained from both the kinetic and product studies. The rate-and product-determining step appears to be an intramolecular nucleophilic attack. The rate coefficients for the rearrangement have been determined for all substrates at 25.0, 35.0 and 45.0 ЊC. The activation parameters have been calculated. The kinetic solvent isotope, solvent and salt effects have been studied. The effects of the 5-substituted and 5,6-disubstituents on the rates have been correlated using a modified Hammett equation giving a reaction constant, , equal to 3.4 at 25 ЊC.

The Chemistry of Vicinal Polycarbonyl Compounds

“…The base-catalyzed cleavage reactions reported by Dahn , could proceed via diacyl carbinol rearrangement followed by hydrolysis of the product esters in the strong (aqueous) base used. This will be discussed in detail in the following section.…”

“…A similar situation is found in the base-catalyzed cleavage of indanetrione ( 4a ) and 5- and 6-substituted derivatives of 4a (cf. ref b) which gave o -carboxymandelic acids upon cleavage by hydroxide ion 144b. The authors considered both reactions 2 and 3 as mechanistic possibilities but did not refer to reaction 4.…”

Effect of Substituents on the Reactivity of Ninhydrin with Urea

“…To fit the kinetic data of the reaction of urea with substituted ninhydrins in a Hammett plot, the 5‐position was taken as para‐ substituted and logically we chose the meta ‐parameter for 4‐substituted ninhydrins . Bowden and Rumpal fitted several Hammett parameters in their kinetic studies of the hydration of indanetrione and the ring fission of ninhydrin and found that the 5‐position of indanetrione and ninhydrin correlates best with the para‐ parameter.…”