Theoretical and experimental study demonstrates kinetic control in chalcone-flavanone transformation of naphthalene derivatives

The condensation of 1'-hydroxy-2'-acetonaphthone with 1- or 2-naphthaldehyde produced the corresponding stable chalcones: C1 or C2. However, the condensation product of either naphthaldehyde with 2'-hydroxy-1'-acetonaphthone yielded chalcones that convert to flavanones- F1 and F2- upon recrystallization. Crystal structures for C1, F1 and F2 are described. Transition state theory estimated rate constants, based on the calculated DFT M052X/6-311 + G(d,p) Gibbs Free energies, show that the rate delimiting step is the cyclization of the chalconate in protic polar solvent. The thermodynamically preferred product is always the flavanone, therefore, the yielding of one or other product is kinetically controlled. (C) 2017 Elsevier B.V. All rights reserved.