Chemo-selective hydrolysis of the iminic moiety in salicylaldehyde semicarbazone promoted by ruthenium

Abstract

ortho-Hydroxybenzaldehyde semicarbazone (salicylaldehyde semicarbazone) undergoes chemo-selective hydrolysis of the iminic carbon nitrogen double bond through its reaction with [RuCl 2(dmso) 4] in ethanol in the presence of water, yielding free salicylaldehyde and semicarbazide that remains coordinated to the ruthenium ion as a bidentate N,O-donor to afford [RuCl 2(dmso) 2(semicarbazide)] · 2H 2O complex. The ruthenium–semicarbazide complex has been characterized by 1H NMR and FTIR spectroscopies and X-ray diffraction methods. Related semicarbazones, derived from p-hydroxybenzaldehyde and benzaldehyde, were not hydrolyzed under the same conditions, suggesting a significant role of the structural o-hydroxy motive in the reaction. Theoretical studies were performed in order to gain further insight on the mechanism of reaction. Results support the hypothesis that the ortho-hydroxy moiety, in the keto tautomeric form, participates in the chemo-selective hydrolysis promoted by [RuCl 2(dmso) 4].