Ring-chain tautomerism of 2-aryl-substituted cis- and trans-decahydroquinazolines

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Abstract

In CDCl3 at 300 K, 2-aryl-substituted cis- and trans-3-isopropyldecahydroquinazolines and trans-3-phenyldecahydroquinazolines proved to be three-component (r1-o-r2) ring-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 Kx = ρσ + log Kx=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.

Original languageEnglish
Pages (from-to)4734-4741
Number of pages8
JournalJournal of Organic Chemistry
Volume67
Issue number14
DOIs
Publication statusPublished - Jul 12 2002

ASJC Scopus subject areas

  • Organic Chemistry

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