The [Cu]-catalyzed SNAR reactions: direct amination of electron deficient aryl halides with sodium azide and the synthesis of arylthioethers under Cu(II)–ascorbate redox system

Synthesis and Photolysis Properties of a New Chloroquine Photoaffinity Probe

A new chloroquine-derived photoaffinity probe has been prepared by a convergent synthesis from derivative of 4,7-dichloroquinoline and N1,N1-diethyl-N4-methylpentane. The features of this probe are a unique 3-azido photolabel, the pyridine ring of the quinoline, and the presence of a secondary amine at the 4-position of the quinoline. These features, particularly the 4-amino methylation, prevent triazole formation through combination of the 3-azide and the 4-amine. This undergoes facile cleavage with exposure to a medium-pressure mercury lamp with a 254 nm excitation wavelength. Trapping of the nitrene byproduct is accomplished with its reaction with N-phenylmaleimide as its cycloazidation product. The structure of a ring-opened DBU amine has been structurally characterized.

Copper(I) Chloride Mediated Amination of Halobenzenes via Azides: Scope, Mechanistic Aspects, and C-C Cleavage Reactions

Selective azidation-amination of long-chain alkanoyl halobenzenes with sodium azide, promoted by copper(I) chloride, is reported. The protocol is, apart from CuCl and NaN₃, additive free and allows the isolation of versatile amine-azides. Alkyl cleavage occurs as a side reaction through an unusual Schmidt-type azide insertion adjacent to the carbonyl group, forming alkyl nitriles possibly via radical pathways. Mechanistic studies involving ¹⁵N labeling experiments and test substrates indicate that the reaction occurs via 1-azido-4-alkanoyl benzenes. The amination is applicable for substrates with electron-withdrawing groups and proceeds under mild conditions. The mechanism of the amine formation involves nitrenes. Intermediates were trapped by carrying out the reaction in the presence of the 2,2,6,6-(tetramethylpiperidin-1-yl)oxyl stable radical and characterized by high-resolution mass spectrometry. The intermediates are consistent with earlier mechanistic proposals.

Synthesis of defined mono-de-N-acetylated β-(1→6)-N-acetyl-d-glucosamine oligosaccharides to characterize PgaB hydrolase activity

Many clinically-relevant biofilm-forming bacterial strains produce partially de-N-acetylated poly-β-(1→6)-N-acetyl-d-glucosamine (dPNAG) as an exopolysaccharide. In Gram-negative bacteria, the periplasmic protein PgaB is responsible for partial de-N-acetylation of PNAG prior to its export to the extracellular space. In addition to de-N-acetylase activity found in the N-terminal domain, PgaB contains a C-terminal hydrolase domain that can disrupt dPNAG-dependent biofilms and hydrolyzes dPNAG but not fully acetylated PNAG. The role of this C-terminal domain in biofilm formation has yet to be determined in vivo. Further characterization of the enzyme's hydrolase activity has been hampered by a lack of specific dPNAG oligosaccharides. Here, we report the synthesis of a defined mono de-N-acetylated dPNAG penta- and hepta-saccharide. Using mass spectrometry analysis and a fluorescence-based thin-layer chromatography (TLC) assay, we found that our defined dPNAG oligosaccharides are hydrolase substrates. In addition to the expected cleavage site, two residues to the reducing side of the de-N-acetylated residue, minor cleavage products on the non-reducing side of the de-N-acetylation site were observed. These findings provide quantitative data to support how PNAG is processed in Gram-negative bacteria.

Sodium sulfate–hydrogen peroxide–sodium chloride adduct: selective protocol for the oxidative bromination, iodination and temperature dependent oxidation of sulfides to sulfoxides and sulfones

Sodium sulfate–hydrogen peroxide–sodium chloride adduct: selective protocols for anilines and sulfides oxidation.

Copper-Catalyzed Multicomponent Domino Reaction of 2-Bromobenzaldehydes, Aryl Methyl Ketones, and Sodium Azide: Access to 1 H-[1,2,3]Triazolo[4,5- c]quinoline Derivatives

A practical copper-catalyzed multicomponent reaction has been developed for the synthesis of 1 H-[1,2,3]triazolo[4,5- c]quinoline derivatives from commercially available 2-bromobenzaldehydes, aryl methyl ketones, and sodium azide. This protocol integrated consecutive base-promoted condensation, [3 + 2] cycloaddition, copper-catalyzed S_NAr, and denitrogenation cyclization sequences. Preliminary mechanistic studies revealed that CuBr₂ acted as a multifunctional catalyst to streamline this domino process. The mild catalytic system enabled effective construction of one C-C and four C-N bonds in one operation.

Probing the hydrolytic reactivity of 2-difluoromethyl pyrroles

α-Difluoromethyl pyrroles were found to be stable while N-protected with an electron-withdrawing group. Due to the propensity of pyrroles to access azafulvenium-like intermediates, the C-F bonds of an α-difluoromethyl substituent are labile under hydrolytic conditions. The presence of certain electron-withdrawing substituents about the pyrrolic ring can accelerate this process, as determined through a kinetic comparison of the deprotection and subsequent hydrolysis reactions of N-protected β-aryl α-difluoromethyl pyrroles.

Copper-mediated reduction of azides under seemingly oxidising conditions: catalytic and computational studies

The reduction of aryl azides in the presence of water and air and without an obvious reducing agent is reported.

The synthesis of substituted amino[2.2]paracyclophanes

Amino[2.2]paracyclophanes can be prepared by direct amination of bromo[2.2]paracyclophanes or more generally by a formylation–oxime formation–oxidation–Lossen-like rearrangement sequence.

A copper catalyzed multicomponent cascade redox reaction for the synthesis of quinazolinones

A copper catalyzed multicomponent cascade redox reaction for the synthesis of various quinazolinones starting from easily available 2-bromobenzamides, benzylic alcohols and sodium azide as a nitrogen source has been developed.

Design, synthesis, and biological activity of oxime ether strobilurin derivatives containing indole moiety as novel fungicide

Twenty-one novel oxime ether strobilurins containing indole moiety, which employed an indole group to stabilize the E-styryl group in Enoxastrobin, were designed and synthesized. The biological assay indicated that most compounds exhibited potent fungicidal activities. The structure-activity relationship study demonstrated that the synthesized methyl 3-methoxypropenoate oxime ethers 7b-e exhibited remarkably high activities among all the synthesized oxime ether compounds 7. Moreover, the fungicidal activities of methyl α-(methoxyimino)benzeneacetate oxime ethers compounds 7f-i and N-methoxy-carbamic acid methyl esters compounds 7j-m showed significant differences compared to the corresponding products of ammonolysis.

2-Aroylindoles from o-bromochalcones via Cu(i)-catalyzed SNAr with an azide and intramolecular nitrene C–H insertion

A simple procedure for the synthesis of 2-aroylindole derivatives comprising a one-pot CuI-catalyzed S_NAr reaction ofo-bromochalcones with sodium azide and subsequent intramolecular cyclization through nitrene C–H insertion has been developed.

An odorless, one-pot synthesis of nitroaryl thioethers via SNAr reactions through the in situ generation of S-alkylisothiouronium salts

The synthesis of nitroaryl thioethers using thiourea as the sulfur source in water by an odorless one-pot process was disclosed.

Consecutive condensation, C-N and N-N bond formations: a copper- catalyzed one-pot three-component synthesis of 2H-indazole

2H-Indazoles are synthesized using copper-catalyzed, one-pot, three-component reactions of 2-bromobenzaldehydes, primary amines, and sodium azide. A copper catalyst plays the key role in the formation of C-N and N-N bonds. This method has a broad substrate scope with a high tolerance for a variety of functional groups.