Metal-free activation of H2O2 by synergic effect of ionic liquid and microwave: chemoselective oxidation of benzylic alcohols to carbonyls and unexpected formation of anthraquinone in aqueous condition

• Published in: Molecular diversity Vol. 15; no. 3; pp. 687 - 695
• Main Authors: Kumar, Rakesh, Sharma, Nandini, Sharma, Naina, Sharma, Abhishek, Sinha, Arun K.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.08.2011; Springer Nature B.V
• Subjects: Anthraquinones - chemistry; Aqueous chemistry; Benzyl Alcohols - chemistry; Biochemistry; Biomedical and Life Sciences; Catalysis; Chemical reactions; Full-Length Paper; Hydrogen peroxide; Hydrogen Peroxide - chemistry; Ionic Liquids - chemistry; Ions; Life Sciences; Microwaves; Organic Chemistry; Oxidation; Oxidation-Reduction; Pharmacy; Polymer Sciences; Ionic liquids; Microwave; Oxidation; Metal-free; Hydrogen peroxide
• ISSN: 1381-1991; 1573-501X
• DOI: 10.1007/s11030-010-9292-z

H 2 O 2 mediated oxidation of alcohols in ionic liquid is revisited, wherein, ionic liquids under the influence of microwave irradiation have been found to facilitate activation of H 2 O 2 without any metal catalyst in aqueous condition. The method utilizes a neutral ionic liquid [hmim]Br both as catalyst and solvent for efficient and chemoselective oxidation of benzyl alcohol derivatives on aromatic ( β, γ ) alcohols, cyclic and aliphatic analogues, which can be a useful synthetic approach in total synthesis of complex organic compounds/natural products. Moreover, an unexpected oxidation of 9-anthracenyl propanol, a polyaromatic benzyl alcohol, resulting in the formation of 9,10-anthraquinone by the loss of propyl side chain was observed. Plausible mechanism and further exploration of this method on various other related substrates are discussed in detail.