title: Ring[bond]chain tautomerism of 2-Aryl-substituted cis- and trans-decahydroquinazolines.
abstract: In CDCl(3) at 300 K, 2-aryl-substituted cis- and trans-3-isopropyldecahydroquinazolines and trans-3-phenyldecahydroquinazolines proved to be three-component (r(1)[bond]o[bond]r(2)) ring[bond]chain tautomeric mixtures, whereas only ring-closed tautomers could be detected for the 3-methyl-substituted analogues. The proportions of the ring-chain tautomeric forms at equilibrium were strongly influenced by the N-substitutents and the cis-trans ring junction and could be described by the equation log K(X) = rho sigma(+) + log K(X=H). These are the first examples among 2-aryl-1,3-N,N-heterocycles of a three-component ring-chain tautomeric equilibrium characterized by a Hammett-type equation. The stabilities of the ring-closed forms of cis- and trans-2-aryldecahydroquinazolines and the corresponding 3,1-benzoxazines were found to increase in the following sequence of the heteroatom at position 3: NPh < N-i-Pr < O < NMe.
authors.affiliation: Institute of Pharmaceutical Chemistry, University of Szeged, H-6701 Szeged, POB 121, Hungary.
authors.forename: László
authors.initials: L
authors.lastname: Lázár
authors.forename: Anikó
authors.initials: A
authors.lastname: Göblyös
authors.forename: Tamás A
authors.initials: TA
authors.lastname: Martinek
authors.forename: Ferenc
authors.initials: F
authors.lastname: Fülöp