IRON-INDUCED ACTIVATION OF HYDROGEN-PEROXIDE FOR THE DIRECT KETONIZATION OF METHYLENIC CARBON [C-C6H12-]C-C6H10(O)] AND THE DIOXYGENATION OF ACETYLENES AND ARYLOLEFINS

In pyridine/acetic acid solvent bis(picolinato)iron(II) [Fe(PA)2], (2,6-dicarboxylatopyridine)iron(II) [Fe(DPA)], and their μ-dimers [(PA)2FeOFe(PA)2 and (DPA)FeOFe(DPA)] catalyze hydrogen peroxide for the selective ketonization of methylenic carbons (>CH2 → >C=O) and the dioxygenation of acetylenes to α-diketones and arylolefins to aldehydes. Cyclohexane is transformed with 72% efficiency (c-C6H12 oxidized per two HOOH) to give 95% cyclohexanone and 5% cyclohexanol, ethyl benzene with 51% efficiency to give acetophenone as the only detectable product, and n-hexane with 52% efficiency to give 53% 3-hexanone, 46% 2-hexanone, and <2% 1-hexanol. Suspensions of KO2(s) or (Me4N)O2(s) in a pyridine/acetic acid solvent system are catalyzed by several iron complexes [(py)4FeCl2, (py)4Fe(OAc)2, FeCl36H2O, (MeCN)4Fe(C1O4)2, (Ph3PO)4Fe(C1O4)2, Fe(PA)2, and (PA)2FeOFe(PA)2] to give HOOH and transform methylenic carbons to ketones, and to dioxygenate acetylenes and arylolefins. Electrolytic reduction of dioxygen (O2) in the same solvent/catalyst systems results in analogous substrate transformations. The Fe(PA)2 complex is uniquely efficient and exhibits catalytic turnover for KO2(s) suspensions as well as for electro-reduced O2. All systems appear to produce a common reactive intermediate 3 [(PA)2FeOOFe(PA)2] via in situ formation of HOOH and (PA)2FeOFe(PA)2 (1). © 1990, American Chemical Society. All rights reserved.