G. Lamanna et al., THEORETICAL-STUDY OF DEGENERATE BOULTON-KATRITZKY REARRANGEMENTS - SEMIEMPIRICAL AND AB-INITIO PROCEDURES, Journal of molecular structure. Theochem, 452, 1998, pp. 67-74
A theoretical study of degenerate Boulton-Katritzky rearrangements con
cerning the anions of the 3-formylamino-1,2,4-oxadiazole, 3-formylmeth
yl-isoxazole and 3-hydroxy-iminomethyl-1,2,5-oxadiazole has been carri
ed out by using semiempirical MNDO and ab initio Hartree-Fock procedur
es. Different transition structures and reactive pathways were obtaine
d in the two cases. Semiempirical treatment shows asymmetrical transit
ion states and non-concerted processes via symmetrical intermediates.
By contrast, ab initio procedures describe concerted and synchronous p
rocesses involving symmetrically-located transition states. Some comme
nts and criticisms on the theoretical treatment of these typical rearr
angements of five-membered heterocycles are reported. (C) 1998 Elsevie
r Science B.V. All rights reserved.