C(sp2)–H Functionalization of Imidazole at the C2- and C4-Position via Palladium-Catalyzed Isocyanide Insertion Leading to Indeno[1,2-d]imidazole and Imidazo[1,2-a]indole Derivatives

Divergent Conversion of Double Isocyanides with Alkenyl Bromide to Polysubstituted Pyrroles and 4-Imino-4,5-dihydropyrrolo[3,4-b]pyrrol-6(1H)-one Derivatives by Pd-Catalyzed Tandem Cyclization Reactions

Herein a novel and concise approach to pyrrole skeletons via Pd-catalyzed tandem cyclization reactions is investigated. The substrates for the transformation could be readily prepared by phosphoric acid-catalyzed Ugi reactions with available starting materials. In this strategy, two isocyanides participate in sequential isocyanide insertion reactions, and the chemoselectivity of the products is regulated by the steric hindrance of the isocyanide. A plausible mechanism for the formation of the corresponding adducts is proposed.

Iridium-Catalyzed Direct Amidation of Imidazoles at the C-2 Position with Isocyanates in the Presence of Hydrosilanes Leading to Imidazole-2-Carboxamides

Regioselective coupling reaction of N-substituted imidazoles with isocyanates in the presence of a stoichiometric amount of hydrosilanes catalyzed by Ir4(CO)12 to give imidazole-2-carboxamides is reported. Imidazoles bearing an (O-silyl)carboximidate group at the 2-position appear to be initially formed in the reaction; these are then hydrolyzed to the final products in situ. The addition of the hydrosilane was essential for the catalytic reaction to proceed. Substituents on the imidazole ring had no effect on the reaction, except for certain bulky substituents such as t Bu and Ph groups at the 4-position. Triazoles such as 4-methyl-4H-1,2,4-triazole and 1-methyl-1H-1,2,4-triazole were also applicable to this C–H amidation, and the latter reaction proceeded regioselectively at the carbon atom between the sp3 and sp2 nitrogen atoms of the ring, and not between the two sp2 nitrogen atoms.

Preparation of a Novel pH-responsive Fluorescent Probe Based on an Imidazo[1,2-a]indole Fluorophore and its Application in Detecting Extremely Low pH in Saccharomyces cerevisiae

A novel pH-responsive probe based on an imidazo[1,2-a]indole fluorophore architecture is reported. The probe was highly selective to strongly acidic pH (pKa = 3.56) with high sensitivity and a fast response time (within 30 s). The probe did not demonstrate any fluorescence changes in the presence of interfering metal ions, and it featured excellent reversibility under strongly acidic conditions. The mechanism of detection of the probe was determined to be based on intramolecular charge transfer (ICT) at different pH. The probe was also able to be used for imaging for detecting acidic pH in Saccharomyces cerevisiae.

Visible-light-driven photocyclization reaction: photocatalyst-free mediated intramolecular N–N coupling for the synthesis of 2H-indazole-3-carboxamides from aryl azides

A visible-light-driven photocyclization reaction of aryl azides to access 2H-indazole-3-carboxamides in moderate to excellent yields has been realized efficiently under photocatalyst-free and external additive-free conditions.

The synthesis and structure of an amazing and stable carbonized material Cu-PC@OFM and its catalytic applications in water with mechanism explorations

An amazing and stable carbonized octahedral frame material Cu-PC@OFM was synthesized and characterized through HRTEM, SEM, XRD, XPS, and Raman spectroscopy and nitrogen adsorption/desorption analysis.

Synthesis of diaryl sulfides based on copper-doped OMS-2

We describe a practical protocol for efficiently preparing diaryl sulfide compounds using Cu–OMS-2 as the catalyst. Cu–OMS-2 originates from manganese oxide octahedral molecular sieves modified with copper ions and catalyzes the C–S coupling reaction of substituted thiophenols and aryl halides. This protocol has the advantages of environmental friendliness, simple operation, high yields, good tolerance of functional groups, and the Cu–OMS-2 catalytic material can be recycled several times.