Making Fe(BPBP)-catalyzed C-H and C[double bond, length as m-dash]C oxidations more affordable

• Published in: Organic & biomolecular chemistry 2014-01, Vol.12 (13), p.2062-2070
• Main Authors: Yazerski, Vital A, Spannring, Peter, Gatineau, David, Woerde, Charlotte H M, Wieclawska, Sara M, Lutz, Martin, Kleijn, Henk, Gebbink, Robertus J M Klein
• Format: Article
• Language: English
• Subjects: Biological Products - chemistry; Catalysis; Epoxy Compounds - chemical synthesis; Epoxy Compounds - chemistry; Ferrous Compounds - chemistry; Hydrocarbons - chemistry; Hydrogen Peroxide - chemistry; Molecular Structure; Oxidation-Reduction; Pyridines - chemistry; Pyrrolidines - chemistry
• ISSN: 1477-0520; 1477-0539
• DOI: 10.1039/c3ob42249f

The limited availability of catalytic reaction components may represent a major hurdle for the practical application of many catalytic procedures in organic synthesis. In this work, we demonstrate that the mixture of isomeric iron complexes [Fe(OTf)2(mix-BPBP)] (mix-1), composed of Λ-α-[Fe(OTf)2(S,S-BPBP)] (S,S-1), Δ-α-[Fe(OTf)2(R,R-BPBP)] (R,R-1) and Δ/Λ-β-[Fe(OTf)2(R,S-BPBP)] (R,S-1), is a practical catalyst for the preparative oxidation of various aliphatic compounds including model hydrocarbons and optically pure natural products using hydrogen peroxide as an oxidant. Among the species present in mix-1, S,S-1 and R,R-1 are catalytically active, act independently and represent ca. 75% of mix-1. The remaining 25% of mix-1 is represented by mesomeric R,S-1 which nominally plays a spectator role in both C-H and C[double bond, length as m-dash]C bond oxidation reactions. Overall, this mixture of iron complexes displays the same catalytic profile as its enantiopure components that have been previously used separately in sp(3) C-H oxidations. In contrast to them, mix-1 is readily available on a multi-gram scale via two high yielding steps from crude dl/meso-2,2'-bipyrrolidine. Next to its use in C-H oxidation, mix-1 is active in chemospecific epoxidation reactions, which has allowed us to develop a practical catalytic protocol for the synthesis of epoxides.