Sulfonyl hydrazides as a general redox-neutral platform for radical cross-coupling.

Sulfonyl hydrazides are stable and usually crystalline substances that can be accessed in a variety of ways, including transiently from hydrazones, to achieve a net reductive arylation of carbonyl compounds. We show their utility as versatile radical precursors, as exemplified with seven C-C bond-forming, redox-neutral cross-couplings with activated olefins, alkyl halides, redox-active esters, aryl halides, alkenyl halides, alkynyl halides, and a trifluoromethylating reagent, to forge C(sp)-C(sp), C(sp)-C(sp), and C(sp)-C(sp) bonds. Exogenous redox (chemical, photo/electrochemical) additives are not necessary because these functional groups serve the dual role of radical precursor and electron donor.

Shapeshifting Gabriel Amine Synthesis with Iodo-BCPs.

The Gabriel amine synthesis is a textbook method for the preparation of primary amines from alkyl halides. In this work, we demonstrate a Gabriel amine synthesis with iodo-bicyclopentanes to make aminomethyl bicyclobutanes. DFT studies support the concerted rearrangement of a bicyclo[1.

Nickel-Electrocatalytic Decarboxylative Arylation to Access Quaternary Centers.

There is a pressing need, particularly in the field of drug discovery, for general methods that will enable direct coupling of tertiary alkyl fragments to (hetero)aryl halides. Herein a uniquely powerful and simple set of conditions for achieving this transformation with unparalleled generality and chemoselectivity is disclosed. This new protocol is placed in context with other recently reported methods, applied to simplify the routes of known bioactive building blocks molecules, and scaled up in both batch and flow.

Synthesis of Bicyclo[1.1.0]butanes from Iodo-Bicyclo[1.1.1]pentanes.

We describe a two-step process for the synthesis of substituted bicyclo[1.1.0]butanes.

Amination of Nitro-Substituted Heteroarenes by Nucleophilic Substitution of Hydrogen.

An open-air method for the transition metal-free direct amination of nitro(hetero)arenes by anilines is disclosed. In this methodology, an aromatic C-H bond is substituted via oxidative nucleophilic aromatic substitution of hydrogen (ONSH). Density functional theory calculations and mechanistic studies support a dianion pathway with oxidation by molecular oxygen as the rate-limiting step.

Overcoming Limitations in Decarboxylative Arylation via Ag-Ni Electrocatalysis.

A useful protocol for achieving decarboxylative cross-coupling (DCC) of redox-active esters (RAE, isolated or generated in situ) and halo(hetero)arenes is reported. This pragmatically focused study employs a unique Ag-Ni electrocatalytic platform to overcome numerous limitations that have plagued this strategically powerful transformation. In its optimized form, coupling partners can be combined in a surprisingly simple way: open to the air, using technical-grade solvents, an inexpensive ligand and Ni source, and substoichiometric AgNO, proceeding at room temperature with a simple commercial potentiostat.

Structural and Thermal Characterization of Halogenated Azidopyridines: Under-Reported Synthons for Medicinal Chemistry.

Owing to their participation in Click reactions, bifunctional azides are valuable intermediates in the preparation of medicines and biochemical tool compounds. Despite the privileged nature of pyridines among pharmaceutical scaffolds, reports of the synthesis and characterization of azidopyridines bearing a halogen substituent for further elaboration are almost completely unknown in the literature. As azidopyridines carry nearly equal numbers of nitrogen and carbon atoms, we hypothesized that safety concerns limited the application of these useful bifunctional building blocks in medicinal and biological chemistry.

Virtual Screening for Ligand Discovery at the σ Receptor.

The σ receptor is a transmembrane protein implicated in several pathophysiological conditions, including neurodegenerative disease (J. Pharmacol. Sci.

Novobiocin Enhances Polymyxin Activity by Stimulating Lipopolysaccharide Transport.

Gram-negative bacteria are challenging to kill with antibiotics due to their impenetrable outer membrane containing lipopolysaccharide (LPS). The polymyxins, including colistin, are the drugs of last resort for treating Gram-negative infections. These drugs bind LPS and disrupt the outer membrane; however, their toxicity limits their usefulness.

Substrate binding to BamD triggers a conformational change in BamA to control membrane insertion.

The β-barrel assembly machine (Bam) complex folds and inserts integral membrane proteins into the outer membrane of Gram-negative bacteria. The two essential components of the complex, BamA and BamD, both interact with substrates, but how the two coordinate with each other during assembly is not clear. To elucidate aspects of this process we slowed the assembly of an essential β-barrel substrate of the Bam complex, LptD, by changing a conserved residue near the C terminus.

The Antibiotic Novobiocin Binds and Activates the ATPase That Powers Lipopolysaccharide Transport.

Novobiocin is an orally active antibiotic that inhibits DNA gyrase by binding the ATP-binding site in the ATPase subunit. Although effective against Gram-positive pathogens, novobiocin has limited activity against Gram-negative organisms due to the presence of the lipopolysaccharide-containing outer membrane, which acts as a permeability barrier. Using a novobiocin-sensitive Escherichia coli strain with a leaky outer membrane, we identified a mutant with increased resistance to novobiocin.

Catalytic conversion of diazocarbonyl compounds to imines: applications to the synthesis of tetrahydropyrimidines and β-lactams.

The synthesis of α-carbonylimines by rhodium(II)-catalyzed reactions of α-diazoesters and organic azides has been developed and applied in hetero-Diels-Alder reactions to form highly functionalized tetrahydropyrimidines and in a one-pot, multicomponent transformation between aryldiazoacetates, p-anisyl azide, and an enonediazoacetate to produce β-lactams in high yields and diastereoselectivities.

Tetrahydroquinolines and benzazepines through catalytic diastereoselective formal [4 + 2]-cycloaddition reactions between donor-acceptor cyclopropenes and imines.

Regio- and diastereoselective Lewis acid catalyzed cycloaddition reactions between imines and donor-acceptor cyclopropenes generated from silyl-protected enoldiazoacetates provide direct access to stable cyclopropane-fused tetrahydroquinolines and, with cyclopropane ring opening under mild conditions, to 1H-benzazipine derivatives.