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A new chiral manganese complex ( C1) bearing a tetradentate nitrogen ligand containing chiral bipyrrolidine and benzimidazole moieties was prepared. The structure of C1 was confirmed by ESI-MS and crystallography. This manganese complex is an active catalyst for the asymmetric epoxidation of various olefins with excellent conversion (up to 99 %) and high enantiomeric excess (up to 96 % ee) with hydrogen peroxide as the oxidant in the presence of 2-ethylhexanoic acid or acetic acid. Compared with previous structurally similar manganese complexes with different diamine backbones ( C2, cyclohexanediamine; C3, diamine from L-proline), C1 showed improved asymmetric induction, especially for simple olefins such as styrene derivatives and substituted chromene. The possible reasons for the improvement of the ee values are discussed in the text on the basis of the crystal structures of the manganese complexes. [ABSTRACT FROM AUTHOR]

The manganese and iron complexes with the tetradentate N ligand (1 R,2 R)- N, N'-dimethyl- N, N'-bis(1-methyl-2-benzimidazolylmethyl)cyclohexane-1,2-diamine have been synthesized and characterized. The crystal structure of the manganese complex demonstrates a cis-α configuration. Both the manganese and iron complexes are active catalysts for the asymmetric epoxidation of olefins with H2O2 as an oxidant and acetic acid as an additive. Up to 96 % ee was observed for the epoxidation of α,β-unsaturated ketones at −20 °C. [ABSTRACT FROM AUTHOR]

Highlights from the article: Corrigendum: Manganese Catalysts with C1-Symmetric N4 Ligand for Enantioselective Epoxidation of Olefins In the case of asymmetric epoxidation of -methylstyrene ( B 2t b ), the GC with a CP-Chirasil-Dex CB column did not separate both enantiomers of the epoxide ( B 3t b ). The yield of epoxide can be reduplicated, and even better (82% isolated yield).

A novel series of tetradentate N4 ligands is prepared and successfully applied in the Fe-catalyzed asymmetric epoxidation of a diversity of di- and trisubstituted enones. [ABSTRACT FROM AUTHOR]

Comparable results are obtained using a manganese and iron catalyst. [ABSTRACT FROM AUTHOR]

Abstract: A series of Mn-complexes with tetradentate N4 ligands, introducing aromatic groups into 2-pyridylmethyl positions of N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)ethane-1,2-diamine ( mep ), N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)cyclohexane-trans-diamine ( mcp ), have been synthesized and applied for epoxidation of olefins using H2O2 as the oxidant. The Mn-complexes still possessed an octahedral mononuclear structure in a cis-α topology. These complexes showed good regioselectivity, high yields and turnover frequency (even up to 228,000h−1) with low catalyst loading (0.1–0.01mol%) for epoxidation of a family of olefins (including internal aromatic olefins, internal and terminal aliphatic olefins and diolefins). [Copyright &y& Elsevier]