Chiral Environment around the Metal Center Observed by the Epoxidation with the Iron Complexes of Bleomycin and the Synthetic Analogue

Abstract

cis-β-Methylstyrene is oxidized either with the Fe(III)–H2O2 or with the Fe(II)–O2 complex systems of bleomycin and the synthetic model ligand PYML-6 to give optically active epoxide, showing that the environment around the iron-nucleus is chiral enough to cause asymmetric epoxidation.

Biomimetic Iron‐Catalyzed Asymmetric Epoxidations: Fundamental Concepts, Challenges and Opportunities

“…The above three reports [226,234,235] were the only precedents known for significant asymmetric epoxidation using hydrogen peroxide and a synthetic nonheme iron complex catalyst when the first breakthrough and promising result was reported in 2007. [236] After developing an efficient procedure for the racemic epoxidation of aromatic alkenes, [237,238] an extensive screen of a large number of commercially available chiral amines was undertaken to explore the possibility of an asymmetric version.…”

“…[28] Thus, catalysts based on Ti, [231] Pt [232] and Ru [233] have been reported for asymmetric epoxidations of olefins using hydrogen peroxide. [16] An early attempt for asymmetric epoxidation by a synthetic non-heme Fe catalyst and hydrogen peroxide was reported simultaneously with the aerobic epoxidation using N1 [226] (Table 6, vide supra). [16] An early attempt for asymmetric epoxidation by a synthetic non-heme Fe catalyst and hydrogen peroxide was reported simultaneously with the aerobic epoxidation using N1 [226] (Table 6, vide supra).…”

“…An early example of the aerobic asymmetric epoxidation with a synthetic non‐heme iron complex was reported in 1989 using the iron complex of PYML‐6 (Figure 9) which is a model complex for the antitumour antibiotic bleomycin 226. The attempted aerobic asymmetric epoxidation of cis ‐β‐methylstyrene and trans ‐β‐methylstyrene using complex N1 (n=II, L=O 2 ) and 2‐mercaptothanol as a reducing agent gave surprising results.…”

Asymmetric Oxidation with Hydrogen Peroxide, an Effective and Versatile Oxidant

“…Ohno et al reported that the Fe(III) complex of a pyridine model ligand-6 (PYML-6) of bleomycin catalyzes epoxidation of some olefins using aqueous hydrogen peroxide. Although enantioselectivity and yield are modest, the report is interesting in terms of development of asymmetric oxidation catalysis of abundant iron [27].…”

Iron Catalyzed Highly Enantioselective Epoxidation of Cyclic Aliphatic Enones with Aqueous H2O2

“…[19][20][21][22][23][24][25][26][27] Highly enantioselective epoxidation of difficult substrates such as ,-disubstituted aromatic enones and -alkyl styrenes, not accessible by other methods, have also been described. 23,24 However, a major limitation still resides at the fact that iron catalyzed asymmetric epoxidations have been limited in scope to olefins conjugated to aromatic rings, [19][20][21][22]23,[24][25][26][27][28][29][30][31][32][33][34][35] and remains to be accomplished for aliphatic substrates. Particularly interesting are cyclic aliphatic enones.…”