Reactions of carbonyl compounds in basic solutions. Part 24.1 The mechanism of the base-catalysed ring fission of substituted benzocyclobutene-1,2-diones
GOULD K. J.; HACKER N. P.; MCOMIE J. F. W.; PERRY D. H., J. CHEM. SOC. PERKIN TRANS., PART 1, 1980, NO 8, 1834-1840
作者:GOULD K. J.、 HACKER N. P.、 MCOMIE J. F. W.、 PERRY D. H.
DOI:——
日期:——
Reactions of carbonyl compounds in basic solutions. Part 24.1 The mechanism of the base-catalysed ring fission of substituted benzocyclobutene-1,2-diones
作者:Keith Bowden、M. Vahid Horri
DOI:10.1039/a606310a
日期:——
The rate coefficients for the base-catalysed ring fission of a
series
of substituted benzocyclobutenediones to give the corresponding
2-formylbenzoic acids have been determined in water at 25.0 and
60.0 °C. The effects of 4-substituents and
4,5-di-substituents on the rates have been correlated using a modified
Hammett equation to give a reaction constant, ρ, equal to
ca. 3.6 at 25.0 °C. The activation
parameters have been calculated. The effect of solvent composition on
the rates has been studied. The kinetic solvent isotope effect, product
composition and enrichment in 18O-enriched water have
also been studied. All the evidence indicates a mechanistic pathway
which proceeds by rapid reversible addition of hydroxide anion to the
dione, followed by intramolecular nucleophilic attack on the second
carbonyl group and formation of a carbanionic intermediate.