75164-83-9Relevant academic research and scientific papers
The Kinetics and Mechanism of the Cyclisation of Some 2'-Hydroxychalcones to Flavanones in Basic Aqueous Solution
Old, K. Barry,Main, Lyndsay
, p. 1309 - 1312 (1982)
Rate coefficients for the chalcone-flavanone equilibration reaction have been established for some 2'-hydroxychalcones over the pH range (ca. 8-11) in which their 2'-hydroxy-groups undergo ionisation.The chalcones studied were the parent 2'-hydroxychalcone (I) and its following derivatives: 4'-OMe (II), 6'-OMe (III), 4'-OH (IV), 4',6'-Me2 (V), and 5',6'-benzo (VI).Pseudo-first-order rate coefficients (kobs) which, for the reversible reactions concerned, are the sum of the forward and reverse rate coefficients, were fitted to the kinetic form, kobs=kfA+k'fB+k''aOH- in which k and k' are the rate coefficients for the unimolecular cyclisation of neutral and of ionised chalcones respectively (fA and fB are the fractions of total chalcone present in the neutral and ionised forms at the pH concerned) and where k'' is the second-order rate coefficient for the reverse reaction of flavanone which involves hydroxide ion (activity aOH-).Data analysis gave rate coefficients and pKa values for all but chalcone (IV) which has a different kinetic form.A conjugate addition-elimination mechanism is proposed to account for the pH-rate profiles, one of which differs from that previously reported.Possible effects on rate coefficients of non-bonded interactions between 6'-substituents and carbonyl oxygen are briefly considered but the differences between chalcones with and without 6'-substituents are sufficiently small to deter prolonged discussion.There seems to be little serious hindrance of cyclisation for any of the 6'-substituted chalcone anions.
Intramolecular Michael-type Addition in the Solid State
Goud, B. Satish,Panneerselvam, Kaliyamoorthy,Zacharias, David E.,Desiraju, Gautam R.
, p. 325 - 330 (2007/10/02)
Several substituted 2'-hydroxy-4',6-dimethylchalcones undergo a solid state intramolecular Michael-type addition reaction to yield the corresponding flavanones, at temperatures significantly below the melting points of the reactants or products.Single crystal X-ray diffraction studies of the reactant and product phases have beeen carried out and indicate that these solid state reactions most likely proceed in a non-topochemical fashion.A similar conclusion is deduced from X-ray powder diffraction, differential scanning calorimetry and packing energy calculations.Reaction in the defect regions is probably important because considerable relaxation in the molecular conformation of the chalcone is required in the crystal before intramolecular ring-closure to the flavanone can occur.
