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

摘要

ortho-Hydroxybenzaldehyde semicarbazone (salicylaldehyde semicarbazone) undergoes chemo-selective hydrolysis of the iminic carbon nitrogen double bond through its reaction with [RuCl2(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 [RuCl2(dmso)(2)(semicarbazide)] center dot 2H(2)O complex. The ruthenium-semicarbazide complex has been characterized by H-1 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 [RuCl2(dmso)(4)]. (c) 2005 Elsevier B.V. All rights reserved.