Oxidovanadium complexes with tridentate aroylhydrazone as catalyst precursors for solvent-free microwave-assisted oxidation of alcohols

• Oxidovanadium complexes with tridentate aroylhydrazone are synthesized.
• X-ray crystal structures are reported.
• Complexes are catalysts for solvent-free microwave-assisted oxidation of alcohols.
• High yields of ketones are achieved.

Aroylhydrazone oxidovanadium compounds, viz. the oxidoethoxidovanadium(V) [VO(OEt)L] (1) (H2L = salicylaldehyde-2-hydroxybenzoylhydrazone), the salt like dioxidovanadium(V) (NH3CH2CH2OH)+[VO2L]− (2), the mixed-ligand oxidovanadium(V) [VO(hq)L] (Hhq = 8-hydroxyquinoline) (3) and the vanadium(IV) [VO(phen)L] (phen = 1,10-phenanthroline) (4) complexes (3 and 4 obtained by the first time), have been tested as catalysts for solvent-free microwave-assisted oxidation of aromatic and alicyclic secondary alcohols with tert-butylhydroperoxide. A facile, efficient and selective solvent-free synthesis of ketones was achieved with yields up to 99% (TON = 497, TOF = 993 h−1 for 3) and 58% (TON = 291, TOF = 581 h−1 for 2) for acetophenone and cyclohexanone, respectively, after 30 min under low power (25 W) microwave irradiation.

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