The present invention relates to a method of preparing a chiral alpha- or beta-substituted ketone from the corresponding beta- or gamma-substituted aldehyde, wherein the ketone has formula (I), (III) or (V), and the corresponding aldehyde has formula (II), (IV) or (VI), respectively, the method comprising reacting the aldehyde of formula (II), (IV) or (VI) in the presence of an amine, oxygen and an organic solvent, wherein the reaction is carried out in the absence of a metal-based catalyst or a metal-based oxidant, wherein: R is H, a substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C15 alkenyl, substituted or unsubstituted C2-C15 alkynyl, substituted or unsubstituted C3-C15 cycloalkyl, substituted or unsubstituted C3-C15 cycloalkenyl, substituted or unsubstituted C3-C15 heterocycloalkyl, substituted or unsubstituted C3-C15 heterocycloalkenyl, substituted or unsubstituted C6-C15 aryl, or substituted or unsubstituted C6-C15 heteroaryl; and R' is H, a substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C15 alkenyl, substituted or unsubstituted C2-C15 alkynyl, substituted or unsubstituted C3-C15 cycloalkyl, substituted or unsubstituted C3-C15 cycloalkenyl, substituted or unsubstituted C3-C15 heterocycloalkyl, substituted or unsubstituted C3-C15 heterocycloalkenyl, substituted or unsubstituted C6-C15 aryl, or substituted or unsubstituted C6-C15 heteroaryl.