A magnesium-catalyzed
regiodivergent C–O bond cleavage protocol
is presented. Readily available magnesium catalysts achieve the selective
hydroboration of a wide range of epoxides and oxetanes yielding secondary
and tertiary alcohols in excellent yields and regioselectivities.
Experimental mechanistic investigations and DFT calculations provide
insight into the unexpected regiodivergence and explain the different
mechanisms of the C–O bond activation and product formation.
Bis(pyrazolyl)methane ligands are excellent components of model complexes used to investigate the activity of the enzyme tyrosinase. Combining the N donors 3-tert-butylpyrazole and 1-methylimidazole results in a ligand that is capable of stabilising a (μ-η(2) :η(2) )-dicopper(II) core that resembles the active centre of tyrosinase. UV/Vis spectroscopy shows blueshifted UV bands in comparison to other known peroxo complexes, due to donor competition from different ligand substituents. This effect was investigated with the help of theoretical calculations, including DFT and natural transition orbital analysis. The peroxo complex acts as a catalyst capable of hydroxylating a variety of phenols by using oxygen. Catalytic conversion with the non-biological phenolic substrate 8-hydroxyquinoline resulted in remarkable turnover numbers. In stoichiometric reactions, substrate-binding kinetics was observed and the intrinsic hydroxylation constant, kox , was determined for five phenolates. It was found to be the fastest hydroxylation model system determined so far, reaching almost biological activity. Furthermore, Hammett analysis proved the electrophilic character of the reaction. This sheds light on the subtle role of donor strength and its influence on hydroxylation activity.
We demonstrate that
aryltriazenes can promote three distinctive
types of C–H functionalization reactions, allowing the preparation
of complex benzene molecules with diverse substitution patterns. 2-Triazenylbenzaldehydes
are shown to be efficient substrates for Rh(I)-catalyzed intermolecular
alkyne hydroacylation reactions. The resulting triazene-substituted
ketone products can then undergo either a Rh(III)-catalyzed C–H
activation, or an electrophilic aromatic substitution reaction, achieving
multifunctionalization of the benzene core. Subsequent triazene derivatization
provides traceless products.
A combined palladium/photoredox catalytic system for the efficient oxidation of terminal olefins to the corresponding methyl ketones is presented. The interplay of air, water, and light leads to a protocol in which the stoichiometric oxidants required for oxidative palladium catalysis are substituted with catalytic, single‐electron transfer processes. Detailed mechanistic investigations revealed the role of the key components, in situ generated species, and catalysts. A broad range of substrates was examined in homogeneous as well as heterogeneous photoredox protocols, delivering the desired products in good yields.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.