Semi-stoichiometric oxidation of benzylic alcohols to benzaldehydes was readily achieved in heated toluene in the presence of cobalt-doped birnessite MnO 2 under oxygen atmosphere. The oxidation took place selectively for benzylic alcohols, while allylic alcohols were oxidized slowly. No oxidation occurred for usual primary and secondary alcohols. Oxygen atmosphere was important to perform effective oxidation; i.e. the oxidation progressed much slower in nitrogen atmosphere. Cobalt-doped birnessite was the best catalyst for the oxidation, in which the amount of birnessite was reduced to 0.7 equivalent of alcohol, resulting in yields of aldehydes greater than 80%. The present method provides a useful green oxidation for benzylic alcohols.

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Atmosphere. -The title reaction takes place selectively with benzylic alcohols (I), whereas allylic alcohols such as (III) are oxidized quite slowly. No oxidation or poor yields are found in the oxidation of usual primary and secondary alcohols. Oxygen atmosphere is required to perform effective transformation, i.e. the oxidation progress is much slower in nitrogen atmosphere. -(KAMIMURA*, A.; NOZAKI, Y.; NISHIYAMA, M.; NAKAYAMA, M.; RSC Adv. 3 (2013) 2, 468-472, http://dx.doi.org/10.1039/c2ra22117a ; Dep. Appl. Mol. Biosci., Grad. Sch. Med., Yamaguchi Univ., Ube, Yamaguchi 755, Japan; Eng.) -S. Karsten 21-034

K-birnessite (also called as δ-type MnO2), prepared by thermal decomposition of KMnO4, is developed as a novel oxidizing reagent. -(KAMIMURA*, A.; NOZAKI, Y.; ISHIKAWA, S.; INOUE, R.; NAKAYAMA, M.; Tetrahedron Lett. 52 (2011) 4, 538-540, http://dx.