POP art: Rhodium complexes of POP ligands serve as highly efficient and enantioselective catalysts in asymmetric hydrogenation leading to various valuable pharmaceutical building blocks and several ...direct precursors of chiral drugs such as LY2497282, lacosamide, rivastigmine, and aprepitant and 12 further examples (see scheme; nbd=norbornadiene; XC(O)G=NHAc, NHBoc, NHCbz, 2‐oxopyrrolidin‐1‐yl, OAc).
The preparation of a library of new P‐O‐P ligands (phosphine‐phosphites and phosphine‐phosphinites), easily available in two synthetic steps from enantiopure Sharpless epoxy ethers, is reported. The ...“lead” catalyst of the series has proven to have outstanding catalytic properties in the rhodium‐catalysed asymmetric hydrogenation of a wide variety of functionalised alkenes (16 examples). The excellent performance and modular design of the catalysts makes them attractive for future applications.
Herein an overview of reductive catalytic enantioselective desymmetrisation of achiral or
meso
compounds is provided. The most efficient reductive desymmetrisations described in the literature, which ...involve the reduction of C&z.dbd;O, C&z.dbd;N, C&z.dbd;C and C-halogen bonds, or reductive ring-opening, are summarised. The structural diversity of the valuable highly enantioenriched intermediates prepared by reductive desymmetrisation is highlighted.
Efficient catalytic enantioselective desymmetrisations, which involve C&z.dbd;O, C&z.dbd;N, C&z.dbd;C and C-halogen bond reduction or reductive ring-opening, are summarised.
The design of artificial catalysts able to compete with the catalytic proficiency of enzymes is an intense subject of research. Non-covalent interactions are thought to be involved in several ...properties of enzymatic catalysis, notably (i) the confinement of the substrates and the active site within a catalytic pocket, (ii) the creation of a hydrophobic pocket in water, (iii) self-replication properties and (iv) allosteric properties. The origins of the enhanced rates and high catalytic selectivities associated with these properties are still a matter of debate. Stabilisation of the transition state and favourable conformations of the active site and the product(s) are probably part of the answer. We present here artificial catalysts and biomacromolecule hybrid catalysts which constitute good models towards the development of truly competitive artificial enzymes.
Supramolecular interactions were used for the design of catalytic enzyme mimics that possess one or more of the properties of enzymes. This review discusses successful examples of host-guest catalysts, catalysts operating in water, self-replicators, allosteric catalysts and biomacromolecule hybrid catalysts.
A family of chiral phosphinooxazolines (12a–e) derived from modular, enantiopure β‐amino alcohols has been prepared, and their palladium complexes have been used as chiral mediators in the asymmetric ...allylic alkylation reaction. The oxazoline moiety in 12 contains a C‐4 aryl and a C‐5 alkoxymethyl substituent that can be independently optimized for high catalytic activity and enantioselectivity. A methoxymethyl substituent at C‐5 has been found to provide the best results in terms of enantioselectivity and activity in the alkylation of a diverse family of allylic substrates under both thermal and microwave‐assisted activation. The palladium‐phosphinooxazoline complexes described in this work are remarkably robust, as the enantioselectivity recorded in the asymmetric allylic alkylation remains essentially unchanged in the temperature range between 20 and 130 °C. An unprecedented reversal in enantioselectivity has been observed between 1,3‐diphenylallyl and 1,3‐dimethylallyl alkylation substrates, and the origin of this behavior has been explained by means of ONIOM QM/MM calculations.
A series of heteroleptic ruthenium(II) polypyridyl complexes containing phenanthroline ligands have been designed, synthesized, and characterized. The spectroscopic and electrochemical properties of ...the complexes have been studied in solution and adsorbed onto semiconductor nanocrystalline metal oxide particles. The results show that for two of the ruthenium complexes, bearing electron-donating (−NH2) or electron-withdrawing (−NO2) groups, the presence of the redox-active I−/I3 − electrolyte produces important changes in the interfacial charge transfer processes that limit the device performance. For example, those dyes enhanced the electron recombination reaction between the photoinjected electrons at TiO2 and the oxidized redox electrolyte. In an effort to understand the details of such striking observations, we have monitored the charge transfer reactions taking place at the different interfaces of the devices using time-resolved single photon counting, laser transient spectroscopy, and light-induced photovoltage measurements.
A highly stereoselective catalytic method for the preparation of structurally diverse P-stereogenic oxides has been developed. The approach relies on the ability of rhodium complexes derived from an ...enantiopure P–OP ligand to kinetically resolve racemic α,β-unsaturated phosphane oxides by hydrogenation of the CC motif and formation of highly enantioenriched (or even enantiopure) P-stereogenic oxides. The practicality of the methodology has been demonstrated by the preparation of potentially functional P-chiral molecules for catalytic enantioselective synthesis.
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