Iron‐Catalyzed Asymmetric Epoxidation of Aromatic Alkenes Using Hydrogen Peroxide

Facial triad modelling using ferrous pyridinyl prolinate complexes: synthesis and catalytic applications

“…20 Beller and coworkers reported in 2007 on the use of ligands derived from the L-proline backbone. 39 These ligands were used in the epoxidation of aromatic alkenes (trans-stilbene) and gave for the first time ee's above 20%. Unfortunately no reactions were done on non-aromatic alkenes.…”

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

“…This is a particularly relevant result since there is no alternative method for the asymmetric epoxidation of this type of substrates. Substitution at position ' also provided high enantiomeric excesses (between 85 and 91% ee, entries 14,[19][20][21][22]. Of notice, natural product isophorone (entry 19) was epoxidized in 71% isolated yield and 89% ee.…”

“…10,11,17,18 Recent reports have disclosed successful examples where asymmetric epoxidation is accomplished, in some cases producing high levels of stereoselectivity ( Figure 1). [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.…”

Asymmetric catalysis using iron complexes – ‘Ruthenium Lite’?

“…In a very detailed mechanistic study, Casey was able to 65 obtain evidence which indicated that the hydrogen transfer reaction from 11 to ketones proceeded through a concerted transfer of both proton and hydride. 25 A later molecular modelling study also supported this.…”

“…Because this is a reversible reaction, 100% conversion can only be achieved by removing the acetone from the reaction. By using vacuum to remove all of the solvents after the reaction had reached 65 equilibrium, followed by addition of fresh isopropanol, almost full conversion (ca 99%) to reduction products was successfully achieved, without loss of enantioselectivity. Complex 22, although marginally less active than 2, gave higher ees for certain substrates, e.g.…”