Search

Recent advances in bioorthogonal catalysis are increasing the capacity of researchers to manipulate the fate of molecules in complex biological systems. A bioorthogonal uncaging strategy is presented, which is triggered by heterogeneous gold catalysis and facilitates the activation of a structurally diverse range of therapeutics in cancer cell culture. Furthermore, this solid-supported catalytic system enabled locally controlled release of a fluorescent dye into the brain of a zebrafish for the first time, offering a novel way to modulate the activity of bioorthogonal reagents in the most fragile and complex organs., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The flavoenzyme monoamine oxidase (MAO) regulates mammalian behavioral patterns by modulating neurotransmitters such as adrenaline and serotonin. The mechanistic basis which underpins this enzyme is far from agreed upon. Reported herein is that the combination of a synthetic flavin and alloxan generates a catalyst system which facilitates biomimetic amine oxidation. Mechanistic and electron paramagnetic (EPR) spectroscopic data supports the conclusion that the reaction proceeds through a radical manifold. This data provides the first example of a biorelevant synthetic model for monoamine oxidase B activity., (© 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.)

The Suzuki-Miyaura coupling is one of the few transition-metal-catalyzed C-C bond-forming reactions that have been used in applications ranging from discovery chemistry to manufacturing processes. Although coupling proceeds through the generic three-stage 'oxidative addition, transmetalation, reductive elimination' sequence, there are a number of features that differentiate the Suzuki-Miyaura process from other transition-metal-catalyzed cross-couplings. Most of these features are centered around, or are a consequence of, activation of the boron reagent for transmetalation through one or both of two distinct pathways. This review focuses on the evidence that has been presented for this 'fork in the trail', and the potential to apply such mechanistic insight to the design of reaction conditions., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Complexes of Group 4 metallocenes in the +3 oxidation state and amidoborane or phosphidoborane function as efficient precatalysts for the dehydrocoupling/dehydrogenation of amine-boranes, such as Me(2) NH⋅BH(3). Such Ti(III) -amidoborane complexes are generated in [Cp(2)Ti]-catalyzed amine-borane dehydrocoupling reactions, for which diamagnetic M(II) and M(IV) species have been previously postulated as precatalysts and intermediates., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Asymmetric catalysis is predominantly associated with the use of enantiomerically pure chiral ligands and catalysts. Although racemic chiral catalysts have been employed quite extensively in polymerization, their utility in mainstream organic synthesis and catalyst development has arguably been rather overlooked. This Minireview collates various themes for the strategic application of racemic ligands and catalysts, ranging from the estimation of selectivity and determination of enantiomeric excess, through to control of regio- and stereochemical outcomes, and mechanistic studies. What emerges is a clear picture that, in isolation or in concert with enantiopure catalysts, the "even-handed" approach has much to offer., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Stick or twist: By introducing steric hindrance at the nitrogen atom, stable linear amides bearing an electron-withdrawing α-substituent (Z = Ar, PhSO(2), P(O)(OR)(2), CN, or CO(2)R) can be induced to undergo solvolysis and substitution reactions through an elimination-addition mechanism (see picture). Key to this process is a low barrier to rotation around the amide bond and the α-substituent Z., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Pd and CO--ureally got me! The title reaction proceeds efficiently at 18 degrees C under CO (1 atm) with 5 % [Pd(OTs)(2)(MeCN)(2)] as precatalyst. Depending on the solvents used, either anthranilates or cyclic imides can be obtained in high yields (see picture, BQ = benzoquinone, Ts = 4-toluenesulfonyl).

An even-handed approach: by use of an enantiomerically enriched substrate and study of the changes in enantiomer ratio of substrate under pseudo zero-order conditions, racemic catalysts may be employed to determine whether the enantiomerically pure catalyst would be effective for kinetic resolution of the racemic substrate (see scheme; E=CO 2 Me)., (Copyright © 2001 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.)

Simply reversing the order of addition of aqueous acid and Et 2 O to the Barbier intermediate 1 of the known indium-mediated allylation leads to unprecedented deoxygenative rearrangements [Eq. (a)]., (© 1998 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.)