A nickel-catalyzed reductive cross-coupling of alkylpyridinium salts and aryl bromides has been developed using Mn as the reductant. Both primary and secondary alkylpyridinium salts can be used, and high functional group and heterocycle tolerance is observed, including for protic groups. Mechanistic studies indicate formation of an alkyl radical, and controlling its fate was key to the success of this reaction.
Cross couplings between simple allylic
alcohols and aryl and vinyl
boronic acids are efficiently catalyzed by nickel(0) catalysts and
bidentate N-heterocyclic carbene/phosphine ligands.
The bidentate nature of the ligand is shown to extend catalyst lifetime
and enable high yields of the corresponding cross-coupling products.
X-ray crystallography confirms the bidentate nature of the ligand
scaffold. Multistep cross coupling-alkene/alkyne insertions reactions
are also conducted and the bidentate nature of the substrate makes
the pendant phosphine of the ligand unnecessary.
We introduce the oxidation of long
aliphatic alkanes
using non-thermal,
atmospheric plasma processing as an eco-friendly route for organic
synthesis. A pulsed dielectric barrier discharge in He/O2 gas mixtures was employed to functionalize n-octadecane.
C18 secondary alcohols and ketones were the main products,
with an optimal molar yield of ∼29.2%. Prolonged treatment
resulted in the formation of dialcohols, diketones, and higher molecular
weight oxygenates. Lighter hydrocarbon products and decarboxylation
to CO2 were also observed at longer treatment times and
higher power inputs. A maximum energy yield of 5.48 × 10–8 mol/J was achieved at short treatment times and high
powers, associated with higher selectivity to primary oxygenates.
Direct hydroxylation of alkyl radicals, as well as disproportionation
reactions, are proposed as the main pathways to alcohols and ketones.
The results hold promise for functionalizing long hydrocarbon molecules
at ambient conditions using catalyst-free plasma discharges.
The identification of Yb(OTf) 3 through a multivariable high-throughput experimentation strategy has enabled a unified protocol for the direct conversion of enantioenriched N-acyloxazolidinones to the corresponding chiral esters, amides, and carboxylic acids. This straightforward and catalytic method has shown remarkable chemoselectivity for substitution at the acyclic N-acyl carbonyl for a diverse array of N-acyloxazolidinone substrates. The ionic radius of the Lewis acid catalyst was demonstrated as a key driver of catalyst performance that led to the identification of a robust and scalable esterification of a pharmaceutical intermediate using catalytic Y(OTf) 3 .
Plastics are an extremely important class of materials that are prevalent in all facets of society; however, their widespread use over time, combined with limited end-of-life strategies, has led to increasing levels of waste accumulation. Although currently considered a burden, plastics waste is potentially an untapped feedstock for numerous chemical and manufacturing processes. In this review, we discuss the state of the art of approaches for valorization of plastics waste from a materials research perspective, including previous efforts to utilize plastics waste and recent innovations that have opportunities to add significant value. Although additional progress is necessary, we present several diverse capabilities and strategies for valorization that, when brought together, address end-of-life challenges for plastics at every stage of design and product consumption. In short, a materials research–based framework offers a unique perspective to address the urgent issues posed by plastics, unlocking the potential of polymers and plastics waste.
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