Synthesis and charactensation of unsymmetrical Schiff bases derived from 3,4-diaminopyridine. Crystal and molecular structure of hydrogen-bonded dimers of 3-{[(4-aminopyridin-3-yl)amino]methylene} pentane-2,4-dione

摘要

3,4-Diaminopyridine reacts with 3-ethoxyvinylidene-2,4-pentanedione to form mainly the product of 1:2 substitution 1. 3-([(4-Aminopyridin-3 -yl) amino]methylenel}pentene-2,4-dione 2 is isolated as the monosubstitution product. Reaction of this 'half-unit' with salicylaldehyde results in the formation of the unsymmetrical Schiff base 3. The molecular structure of 3-1[(4-Aminopyridin-3-yl)amino] methylene) pentene-24-dione 2 has been determined by the single crystal X-ray method. Compound 2 forms intermolecular hydrogen-bonded dimers in the crystalline state. The crystal structure of 2 has clearly established that the reaction occurs at the amino group at 3-position of pyridine ring. The dominant tautomeric form of the compounds in solution has been established. (c) 2005 Elsevier B.V. All rights reserved.