Metal-free, efficient hydrazination of imidazo[1,2-a]pyridine with diethyl azodicarboxylate in neutral media

On-surface synthesis of nitrogen-doped nanographene with an [18]annulene pore on Ag(111)

On-surface synthesis is of importance to fabricate low dimensional carbon-based nanomaterials with atomic precision. Here, we synthesize nitrogen-doped nanographene with an [18]annulene pore and its dimer through sequential reactions of debromination, aryl-aryl coupling, cyclodehydrogenation and C-N coupling on Ag(111) from 3,12-dibromo-7,8-diaza[5]helicene. The inner structures of the products were characterized with scanning tunneling microscopy with a CO terminated tip at low temperature. Furthermore, the first four unoccupied electronic states of the nanographene were investigated with a combination of scanning tunneling spectroscopy and theoretical calculations. Except for the LUMO + 2 state observed at +1.3 V, the electronic states at 500 mV, 750 mV and 1.9 V were attributed to the superatom molecular orbitals at the [18]annulene pore, which were significantly shifted towards the Fermi level due to the hybridization with the confined surface state.

Functionalization of Porphyrins Using Metal-Catalyzed C–H Activation

The review is devoted to the C–H functionalization of porphyrins. Porphyrins exhibit the properties of organic semiconductors, light energy converters, chemical and electrochemical catalysts, and photocatalysts. The review describes the iridium- and palladium-catalyzed direct functionalization of porphyrins, with more attention given to the results obtained in our laboratory. The development and improvement of synthetic methods that do not require preliminary modification of the substrate with various functional groups are extremely important for the preparation of new organic materials based on porphyrins. This makes it possible to simplify the synthetic procedure, to make the synthesis more economical, environmentally safe, and simple to perform.

Reaction of imidazo[1,2-a]pyridines with coumarin-3-carboxylic acids: a domino Michael addition/decarboxylation/oxidation/annulation

A palladium-catalyzed decarboxylative domino reaction of imidazo[1,2-a]pyridines and coumarin-3-carboxylic acids has been developed, which provides access to dibenzoisochromenoimidazo[1,2-a]pyridin-6-ones possessing six fused rings.

C(sp3)–H functionalization with isocyanides

This review highlights the state-of-the-art advances in C(sp³)–H functionalization involving isocyanides through the synergistic combination of isocyanide insertion and C(sp³)–H bond activation.

Intramolecular cyclization of imidazo[1,2-a]pyridines via a silver mediated/palladium catalyzed C–H activation strategy

Intramolecular cyclization of imidazo[1,2-a]pyridines has been developed via a C–H activation strategy to reach new chemical-space for drug discovery.

Electrochemical oxidative C–H/N–H cross-coupling for C–N bond formation with hydrogen evolution

We herein report an electrochemical oxidative C–H/N–H cross-coupling reaction in an undivided cell.

Selective, C-3 Friedel-Crafts acylation to generate functionally diverse, acetylated Imidazo[1,2-a]pyridine derivatives

Carbon-carbon bonds are integral for pharmaceutical discovery and development. Frequently, C-C bond reactions utilize expensive catalyst/ligand combinations and/or are low yielding, which can increase time and expenditures in pharmaceutical development. To enhance C-C bond formation protocols, we developed a highly efficient, selective, and combinatorially applicable Friedel-Crafts acylation to acetylate the C-3 position of imidazo[1,2-a]pyridines. The reaction, catalyzed by aluminum chloride, is both cost effective and more combinatorial friendly compared to acetylation reactions requiring multiple, stoichiometric equivalents of AlCl3. The protocol has broad application in the construction of acetylated imidazo[1,2-a]pyridines with an extensive substrate scope. All starting materials are common and the reaction requires inexpensive, conventional heating methods for adaptation in any laboratory. Further, the synthesized compounds are predicted to possess GABA activity through a validated, GABA binding model. The developed method serves as a superior route to generate C-3 acetylated imidazo[1,2-a]pyridine building-blocks for combinatorial synthetic efforts.

Synthesis of Constrained Heterocycles Employing Two Post-Ugi Cyclization Methods for Rapid Library Generation with In Cellulo Activity

Benzimidazoles and quinoxalinones are present in the core of many pharmacologically relevant compounds. Several combinatorial methods have been developed to attach ring systems to both scaffolds for derivatization at select positions. Herein, we describe the development of novel constrained heterocyclic compounds attached to the N1 position of both benzimidazole and quinoxalinone scaffolds. Utilizing robust post-Ugi cyclization methods, including the Ugi-deprotection-cyclization (UDC) methodology, allows for efficient access to a new area of chemical space. Additionally, molecular modeling and in cellulo screening was employed to therapeutically validate the compounds formed with this method.

Visible-light mediated regioselective (phenylsulfonyl)difluoromethylation of fused imidazoles with iododifluoromethyl phenyl sulfone

A visible-light catalyzed direct and regioselective (phenylsulfonyl)difluoromethylation of imidazo[1,2-

Visible-light-mediated C3-azolylation of imidazo[1,2-a]pyridines with 2-bromoazoles

3-Heterocycle-substituted imidazo[1,2-a]pyridines were produced by a visible-light-mediated coupling reaction of imidazo[1,2-a]pyridines with 2-bromoazoles.

Copper-catalyzed carbonylation of anilines by diisopropyl azodicarboxylate for the synthesis of carbamates

Herein, a simple Cu-catalyzed system for the synthesis of carbamates has been developed using anilines with diisopropyl azodicarboxylate as a carbonyl source under solvent-free conditions.

Metal-free C–N bond formations: one-pot synthesis of pyrido[2′,1′:2,3]imidazo[4,5-c]cinnolines, benzo[4′,5']thiazolo- and thiazolo[2′,3′:2,3]imidazo[4,5-c]cinnolines

An efficient one-pot synthesis of novel pyrido[2′,1′:2,3]imidazo[4,5-c]cinnoline derivatives has been achieved with moderate to good yields, with two C–N bond formations through C–H functionalization of 2-arylimidazo[1,2-a]pyridines.

Versatile and highly efficient oxidative C(sp3)–H bond functionalization of tetrahydroisoquinoline promoted by bifunctional diethyl azodicarboxylate (DEAD): scope and mechanistic insights

The oxidant–base bifunctionality of DEAD realized highly reliable cross dehydrogenative coupling of tetrahydroisoquinoline derivatives via aminal intermediates.

Organopromoted direct synthesis of 6-iodo-3-methylthioimidazo[1,2-a]pyridines via convergent integration of three self-sorting domino sequences

An NH₂CN-promoted convergent integration of three self-sorting domino sequences is described for the construction of 6-iodo-3-methylthioimidazo[1,2-a]pyridines from aryl methyl ketones and 2-aminopyridines.

Catalyst-free selenylation of imidazoheterocycles

A simple, efficient, and practical method for the phenylselenylation of imidazo[1,2-a]pyridines via electrophilic substitution employing readily available phenylselenium bromide has been developed in aqueous media at room temperature.