Síntese e caracterização estrutural de compostos do tipo melofen simétricos e não-simétricos

Abstract

Schiff bases with N2O2-tetradentate-type system are effective as coordinating ligands mainly to main group and transition metal. Their applications comprehend new catalysts, bioinorganic chemistry, as well as material science. Schiff bases accessed by condensation of a diamine with two equivalents of salicylaldehyde are often referred as

Salen or Salophens compounds/ligands. The discovery of o-phenylenediamine- bis(methylene Meldrum ́s acid) derivatives as a new family of ligands structurally and

isostericly related of Salophens-type compounds prompted to study the scope and limitations of their syntheses. The o-phenylenediamine-bis(methylene Meldrum ́s acid) derivatives also called Melophen-type compounds have been usually synthesized by refluxing o-phenylene diamines with two equivalents of 5-methoxymethylene or 5- methoxyethylidene Meldrum ́s acid 2 (generated in situ) in adequate orthoester. Herein,

we describe the efficient synthesis of eight novel and known symmetrical Melophen (3a- d; 4a-c; 5a) from condensation o-phenylene diamines with two equivalents of 2 by

heating under reflux, or by keeping under room temperature, using 2 freshly prepared. Additionally, one novel Melophen nonsymmetrical was also synthesized step by step using freshly and previously prepared mono-amine-ethylidene Meldrum ́s acid as precursor. All Melophen ́s molecular structures were confirmed by spectrometric methods.