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Aquest mateix article està publicat a l'edició alemanya de la revista 'Angewandte Chemie' (ISSN 0044-8249, EISSN 1521-3757), vol. 127, núm. 9, p. 2767-2771. DOI http://dx.doi.org/10.1002/ange.201410557 Highly enantioselective epoxidation of -substituted styrenes with aqueous H2O2 is described by using a chiral iron complex as the catalyst and N-protected amino acids (AAs) as coligands. The amino acids synergistically cooperate with the iron center in promoting an efficient activation of H2O2 to catalyze epoxidation of this challenging class of substrates with good yields and stereoselectivities (up to 97%ee) in short reaction times We acknowledge group LIPPSO from UdG for providing amino acid samples and A. Riera (IRB) for access to a polarimeter. We acknowledge financial support from the European Research Council (ERC-2009-StG-239910), MINECO of Spain (CTQ2012-37420-C02-01/BQU, CSD2010-00065), and Generalitat de Catalunya (2009SGR637). J.L.-F. thanks MICINN for a RyC contract. X.R. and M.C. thank ICREA-Academia awards

Bulky iron complexes are described that catalyze the site-selective oxidation of alkyl C-H bonds with hydrogen peroxide under mild conditions. Steric bulk at the iron center is introduced by appending trialkylsilyl groups at the meta-position of the pyridines in tetradentate aminopyridine ligands, and this effect translates into high product yields, an enhanced preferential oxidation of secondary over tertiary C-H bonds, and the ability to perform site-selective oxidation of methylenic sites in terpenoid and steroidal substrates. Unprecedented site selective oxidation at C6 and C12 methylenic sites in steroidal substrates is shown to be governed by the chirality of the catalysts.

An iron complex with a C1-symmetric tetradentate N-based ligand catalyzes the asymmetric epoxidation of cyclic enones and cyclohexene ketones with aqueous hydrogen peroxide, providing the corresponding epoxides in good to excellent yields and enantioselectivities (up to 99% yield, and 95% ee), under mild conditions and in short reaction times. Evidence is provided that reactions involve an electrophilic oxidant, and this element is employed in performing site selective epoxidation of enones containing two alkene sites.

The development of catalysts for the selective oxidation of readily available hydrocarbons or organic precursors into oxygenated products is a long-standing goal in organic synthesis. In the last decade, some iron coordination complexes have shown the potential to fit this role. These catalysts can mimic the O−O activation mode of far more sophisticated iron oxygenase enzymes, generating powerful yet selective oxidants. In this review, we report state-of-the-art C−H and C=C oxidations catalyzed by non-heme iron complexes and H2O2 as the oxidant. Finally, we briefly describe some novel oxidative reactivity and the perspectives of this chemistry We acknowledge financial support from the Ministry of Economy and Competitiveness (MINECO) of Spain and Fondo Europeo de Desarrollo Regional (CTQ2015-70795-P/BQU), Consolider-Ingenio (CSD2010-00065), and the Catalan Department for Innovation, Universities and Enterprise (DIUE) of the Generalitat de Catalunya (2009SGR637)

Iron coordination complexes with nitrogen and oxygen donor ligands have long since been known to react with peroxides producing powerful oxidizing species. These compounds can be regarded as simple structural and functional models of the active sites of non-heme iron dependent oxygenases. Research efforts during the last decade have uncovered basic principles and structural coordination chemistry motifs that permit us to control the chemistry that evolves when these iron complexes react with peroxides, in order to provide powerful metal-based, but at the same time selective, oxidising agents. Oxidation methodologies with synthetic value are currently emerging from this approach. The current review focuses on asymmetric epoxidation, a reaction which has large value in synthesis, and where iron/H2O2 based methodologies may represent not only a sustainable choice, but may also expand the scope of state-of-the-art oxidation methods. Basic principles that underlay catalyst design as well as H2O2 activation are discussed, whilst limitations and future perspectives are also reviewed.

Aquest mateix article esta publicat a l'edicio alemanya de la revista 'Angewandte Chemie' (ISSN 0044-8249, EISSN 1521-3757), vol. 127, num. 9, p. 2767-2771. DOI http://dx.doi.org/10.1002/ange.201410557

Manganese catalysts of the type of MNN and MNO but with a different substitution pattern on the aromatic rings are synthesized and tested with respect to their catalytic activity in the epoxidation reaction of styrene derivatives and steroids.

Electronic effects in the iron catalyst are used to control the activation of hydrogen peroxide and oxygen transfer in a non-porphyrinic catalyst.