The Synthesis And Characterization Of Salicylidene Acylhydrazone Schiff Bases And Its Selective N-alkylation

Acylhydrazone Schiff bases are a class of compounds containing amide and imine functional groups.The N-acylhydrazone moiety is considered a privileged structure in Medicinal Chemistry,since it is stable against hydrolysis and can be recognised by many distinct receptors,leading to a peptide mimetic nature.It has a strong coordination ability containing a pro-transition metal nitrogen atom and a pro-rare-earth metal oxygen atom,which can coordinate with most metal ions.Acylhydrazone Schiff bases and their metal complexes have been widely used in medicine,analysis and functional materials etc.,attracted much attention of scientific researchers.In this thesis,a novel method for the N-alkylation of acylhydrazone was developed and 55 N-alkylated acylhydrazone compounds were synthesized.?1?The fifteen acylhydrazone Schiff base compounds derived from three substituted benzoic acids and non-steroidal anti-inflammatory drugs after esterification,hydrazation and condensation reactions.The experimental operation is easy,post-treatment is simple,and yield exceeds 90%.The N-acylhydrazone are further coordinated with FeCl₃·6H₂O to obtain metal complexs.The synthesized compounds were characterized by ¹H-NMR,¹³C-NMR,FT-IR and elemental analysis.?2?The 55 N-alkylated acylhydrazone Schiff base compounds which have not been reported in the literature,were obtained from the transition metal iron complexes as the intermediates and reacted with the alkylating agent haloalkane and sulfuric acid ester under the action of weak base potassium carbonate.The optimal ethylation reaction conditions were preliminarily explored:the molar ratio of ethyl bromide and diethyl sulfate was 1:4?1.5 eq in total?and the reaction time was approximately 15 h.The long straight butyl group and the bulky benzyl group are further introduced on the amide N atom.Then they were characterized by ¹H-NMR,¹³C-NMR,FT-IR and elemental analysis.The possible reaction mechanism was proposed.A novel method for the N-alkylation of acylhydrazone was developed,which increases a new method in the N-alkylation reaction of these compounds.?3?In order to prove the practicability of selective alkylation of transition metal iron complexes,a large number of literature investigations have revealed a class of N-hydrazide compounds having bioactivity that are condensed by furanoyl hydrazide and salicylaldehyde derivatives.Hydroxyl groups need to be protected and deprotected when the acylhydrazone is derivatized.We optimized this reaction step,succeeded in obtaining N-methyl acylhydrazone 16a using iron metal complexes,and further derive compounds 16d and 17a.