Pd-Catalyzed Tandem Cyclization via C–H Arylation and Acylation for the Construction of Polycyclic Scaffolds

A benzimidazole-based Cu(II) complex catalyzed site-selective C-H sulfenylation of imidazo-[1,2-a]pyridines using CS2 as a sulfur source

A new benzimidazole-based Cu(II) complex catalyzed site-selective sulfenylation of imidazo[1,2-a]pyridines with benzyl/alkyl/allyl bromides and CS2 at 100 °C in DMF : H2O is reported. The present methodology has been developed for the synthesis of 3-sulfenyl imidazo[1,2-a]pyridines in good yields with a broad substrate scope. In this protocol, CS2, commonly known as a non-polar small molecule bioregulator (SMB), is converted to valuable sulfenylated imidazo[1,2-a]pyridine derivatives. In addition, theoretical investigations along with experimental evidence unfold the insights into the probable mechanistic pathway of site-selective sulfenylation from S,S-dibenzyltrithiocarbonate, which is particularly formed as an intermediate during the reaction.

A Magnetically Recyclable Palladium-Catalyzed Formylation of Aryl Iodides with Formic Acid as CO Source: A Practical Access to Aromatic Aldehydes

A magnetically recyclable palladium-catalyzed formylation of aryl iodides under CO gas-free conditions has been developed by using a bidentate phosphine ligand-modified magnetic nanoparticles-anchored­ palladium(II) complex [2P-Fe3O4@SiO2-Pd(OAc)2] as catalyst, yielding a wide variety of aromatic aldehydes in moderate to excellent yields. Here, formic acid was employed as both the CO source and the hydrogen donor with iodine and PPh3 as the activators. This immobilized palladium catalyst can be obtained via a simple preparative procedure and can be facilely recovered simply by using an external magnetic field, and reused at least 9 times without any apparent loss of catalytic activity.

From Synthetic Simplified Marine Metabolite Analogues to New Selective Allosteric Inhibitor of Aurora B Kinase

Significant inhibition of Aurora B was achieved by the synthesis of simplified fragments of benzosceptrins and oroidin belonging to the marine pyrrole-2-aminoimidazoles metabolites isolated from sponges. Evaluation of kinase inhibition enabled the discovery of a synthetically accessible rigid acetylenic structural analogue EL-228 (1), whose structure could be optimized into the potent CJ2-150 (37). Here we present the synthesis of new inhibitors of Aurora B kinase, which is an important target for cancer therapy through mitosis regulation. The biologically oriented synthesis yielded several nanomolar inhibitors. The optimized compound CJ2-150 (37) showed a non-ATP competitive allosteric mode of action in a mixed-type inhibition for Aurora B kinase. Molecular docking identified a probable binding mode in the allosteric site "F" and highlighted the key interactions with the protein. We describe the improvement of the inhibitory potency and specificity of the novel scaffold as well as the characterization of the mechanism of action.

Synthesis of Pyrrolo[2,1,5-cd]indolizine Rings via Visible-Light-Induced Intermolecular [3+2] Cycloaddition of Indolizines and Alkynes

A range of indolizine smoothly underwent visible-light-induced intermolecular [3+2] annulations with internal alkynes to afford pyrrolo[2,1,5-cd]indolizine in good to excellent yields with high regioselectivity. Through this cascade reaction, a series of fluoroactive fused indolizines with a large π-system were conveniently synthesized. The usage of visible light as energy source with air as a stoichiometric oxidant under simple conditions makes this process attractive and practical.

Rh(III)-Catalyzed Tandem Bicyclization of 2-Arylimidazo[1,2-a]pyridines with Cyclic Enones for the Construction of Bridged Scaffolds

An efficient Rh(III)-catalyzed bicyclization of 2-arylimidazo[1,2-a]pyridine with cyclic enones has been developed for the synthesis of bridged imidazopyridine derivatives in excellent yields up to 95%. The reaction proceeds through a sequential conjugate addition of ortho-C-H bond of aryl group followed by an intramolecular C3-alkylation of imidazopyridine ring in a highly regioselective manner.

Synthesis of fused imidazo[1,2-a]pyridines derivatives through cascade C(sp2)-H functionalizations

An efficient and convenient synthesis of diversely substituted naphtho[1',2':4,5]imidazo[1,2-a]-pyridine derivatives from the cascade reactions of 2-arylimidazo[1,2-a]pyridines with a-diazo carbonyl compounds via Rh(iii)-catalyzed regioselective C(sp2)-H alkylation followed by intramolecular annulation is presented. Interestingly, when simple 2-arylimidazo[1,2-a]pyridines were used as the substrates, 5,6-disubstituted naphtho[1',2':4,5]imidazo[1,2-a]pyridines were efficiently obtained, whereas using 2-arylimidazo[1,2-a]pyridine-3-carbaldehydes as the substrates afforded naphtho[1',2':4,5]imidazo[1,2-a]-pyridine-5-carboxylates as the dominating products. Compared with literature methods for the synthesis of naphtho[1',2':4,5]imidazo[1,2-a]pyridine derivatives, the protocol presented herein has advantages such as easily obtainable substrates, simple operational procedure, high efficiency and excellent regio- and chemoselectivity.

Palladium-Catalyzed Hiyama Cross-Couplings of Arylsilanes with 3-Iodoazetidine: Synthesis of 3-Arylazetidines

The first palladium-catalyzed Hiyama cross-coupling reactions of arylsilanes with 3-iodoazetidine were described. The protocol provides a convenient access to a variety of useful 3-arylazetidines which are of great interest in pharmaceutical laboratories in moderate to good yields (30%-88%). In addition, this strategy has the advantage of easy operation and mild reaction conditions.

Nickel-promoted C(2)–H amidation of quinoline N-oxides with N-fluorobenzenesulfonimide

The first example of nickel-promoted C–H amidation of quinoline N-oxides with NFSI.

Crystal structure of 8-(trifluoromethyl)imidazo[1,2-a]pyridine-3-carbaldehyde, C9H5F3N2O

C9H5F3N2O, orthorhombic, Pnma (no. 62), a = 7.276(2) Å, b = 6.7773(19) Å, c = 17.613(5) Å, V = 868.5(4) Å3, Z = 4, R gt(F) = 0.0399, wR ref(F 2) = 0.1122, T = 293(2) K.

Pd-Catalyzed Alkylation of (Iso)quinolines and Arenes: 2-Acylpyridine Compounds as Alkylation Reagents

The first Pd-catalyzed alkylation of (iso)quinolines and arenes is reported. The readily available and bench-stable 2-acylpyridine compounds were used as an alkylation reagent to form the structurally versatile alkylated (iso)quinolines and arenes. The method affords a convenient pathway for the introduction of alkyl groups into organic molecules.

Nickel-Catalyzed Direct C-H Trifluoromethylation of Free Anilines with Togni's Reagent

An efficient nickel-catalyzed C-H trifluoromethylation for the synthesis of trifluoromethylated free anilines using Togni's reagent has been developed. This approach exhibits a good functional group tolerance, good regioselectivity, and chemoselectivity under mild conditions. The newly developed economical one-step method is a better alternative to synthesize trifluoromethylated free anilines.