CuI-catalyzed Sonogashira reaction for the efficient synthesis of 1 H -imidazo[2,1- a ]isoquinoline derivatives

Pd(OAc)2-Catalyzed Synthesis of Imidazo[1,2-f]phenanthridines via a Sequential Ullmann Coupling and Oxidative Coupling Dehydrogenation

The Ullmann coupling and oxidative coupling dehydrogenation reactions have occurred sequentially, catalyzed by Pd(OAc)2, which unexpectedly yielded fused imidazo[1,2-f]phenanthridine derivatives in good to high yields. Structural analysis of the intermediate and final products indicated that the protocol did not include C-H and N-H arylation.

Synthesis of pyrimidine-fused skeletons through copper-catalyzed consecutive Sonogashira coupling and aminocyclization

A copper-catalyzed sequence involving a Sonogashira coupling reaction and 5-exo-dig aminocyclization between a terminal alkyne and a 2-(2-bromophenyl)pyrimidine analog based on six-membered rings is presented. This protocol provides a controlled and modular approach to access a variety of synthetically useful pyrimidine-fused skeletons with high efficiency, broad substrate scope, and excellent functional group compatibility. Under acidic conditions, the (Z)-configuration of products spontaneously converts into (E)-9-benzylidene-1,9-dihydro-11H-pyrazolo[4',3':4,5]pyrimido[2,1-a]isoindol-11-ones.

Recyclable Magnetic Cu-MOF-74-Catalyzed C(sp2)-N Coupling and Cyclization under Microwave Irradiation: Synthesis of Imidazo[1,2-c]quinazolines and Their Analogues

Magnetic Cu-MOF-74 (Fe₃O₄@SiO₂@Cu-MOF-74) was synthesized for the first time by grafting MOF-74 (copper as the metal center) on the surface of core-shell magnetic carboxyl-functionalized silica gel (Fe₃O₄@SiO₂-COOH), which was prepared by coating core Fe₃O₄ nanoparticles with hydrolyzed 2-(3-(triethoxysilyl)propyl)succinic anhydride and tetraethyl orthosilicate. The structure of Fe₃O₄@SiO₂@Cu-MOF-74 nanoparticles was characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM). The prepared Fe₃O₄@SiO₂@Cu-MOF-74 nanoparticles could be applied as a recyclable catalyst to the synthesis of N-fused hybrid scaffolds. 2-(2-Bromoaryl)imidazoles and 2-(2-bromovinyl)imidazoles were coupled and cyclized with cyanamide in DMF in the presence of a catalytic amount of Fe₃O₄@SiO₂@Cu-MOF-74 along with a base to give imidazo[1,2-c]quinazolines and imidazo[1,2-c]pyrimidines, respectively, in good yields. The Fe₃O₄@SiO₂@Cu-MOF-74 catalyst could be easily recovered by a super magnetic bar and recycled more than four times while almost maintaining catalytic activity.

Copper-catalyzed Sonogashira reactions: advances and perspectives since 2014

Transition metal catalyzed Sonogashira coupling reaction has evolved as an efficient pathway for the construction of C-C bonds. Initially, palladium cooperating with copper was considered as the efficient catalytic system for this reaction. However, nowadays there have been astonishing progress in copper catalyzed Sonogashira coupling reactions. Copper catalyzed reactions have attained significant attention owing to the cost effective and environmentally benign characteristics of this metal compared to palladium. This review summarizes the recent developments in copper catalyzed Sonogashira coupling covering literature from 2014 to 2021.

Copper-catalyzed deacetonative Sonogashira coupling

A convenient Pd- and phosphine-free protocol for assembling internal alkynes from tertiary propargyl alcohols and (het)aryl halides has been developed. The proposed tandem approach includes the base-promoted retro-Favorskii fragmentation followed by Cu-catalyzed C(sp)-C(sp²) cross-coupling. The use of inexpensive reagents (e.g. a catalyst, additives, a base, and a solvent) and good functional group tolerance make the procedure practical and cost-effective. The synthetic utility of the method was demonstrated by a smooth alkynylation of vinyl iodides derived from natural steroidal hormones.

Synthesis of Imidazo[1,2-f]phenanthridines by Recyclable Magnetic MOF-Catalyzed Coupling and Cyclization of 2-(2-Bromoaryl)imidazoles with Cyclohexane-1,3-diones Followed by Aromatization

2-(2-Bromoaryl)imidazoles react with cyclohexane-1,3-diones in the presence of a catalytic amount of recyclable Fe₃O₄@SiO₂@MOF-199 and a base to give the corresponding C-C coupled and cyclized products 6,7-dihydroimidazo[1,2-f]phenanthridin-8(5H)-ones in high yields. The magnetic MOF catalyst could be easily recovered and reused four times without any significant loss of catalytic activity. The coupled and cyclized scaffolds were aromatized to imidazo[1,2-f]phenanthridines in high yields by a one-pot sequential procedure including reduction, dehydration, and oxidation. The present protocol could be applied to the synthesis of Zephycandidine A, which is known to exhibit anti-tumor activity.

Recent Advances in Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds

This review surveys recent progress in the chemistry of polycyclic heteroaromatic molecules with a focus on structural diversity and synthetic methodology. The article covers literature published during the period of 2016-2020, providing an update to our first review of this topic (Chem. Rev. 2017, 117 (4), 3479-3716).

CuI-Promoted [3+2] Cycloaddition/oxidation to construct Pyrrolo[2,1a]isoquinolino-quinones from naphthoquinone and tetrahydroisoquinoline

The copper-catalyzed three-component one-pot 1,3-dipole cycloaddition/oxidation has been developed to construct Pyrrolo[2,1-a]isoquinolinoquinone derivatives with environmentally friendly oxygen as the oxidant. The products Pyrrolo[2,1-a]isoquinolinoquinones were obtained from the naturally available raw materials tetrahydroisoquinoline, 1,4-naphthoquinone and benzaldehyde with medium yields.

Microwave-assisted green construction of imidazole-fused hybrid scaffolds using 2-aminobenzimidazoles as building blocks

A class of trinuclear imidazole-fused hybrid scaffolds was constructed by the reaction of 2-(2-bromoaryl)- and 2-(2-bromovinyl)imidazoles with 2-aminobenzimidazoles as building blocks in the presence of a base under microwave irradiation. A nucleophilic aromatic substitution followed by cyclization is proposed as a reaction pathway of this green process.

A green synthesis of trinuclear imidazole-fused hybrid scaffolds has been developed by transition metal-free double C(sp²)–N coupling and cyclization of 2-(2-bromoaryl)- and 2-(2-bromovinyl)imidazoles with 2-aminobenzimidazoles as building blocks under microwave irradiation.

Nonmetal-catalyzed hydroamination of ynamides with amines

A TfOH-catalyzed hydroamination of ynamides with primary and secondary amines under mild reaction conditions is described for the efficient synthesis of N-arylimines and ethene-1,1-diamines.

Construction of Binuclear Benzimidazole-Fused Quinazolinones and Pyrimidinones Using Aryl Isocyanates as Building Blocks by Transition-Metal-Free C(sp2)-N Coupling

A class of binuclear N-fused hybrid scaffolds was constructed by the reaction of 2-(2-bromoaryl)- and 2-(2-bromovinyl)benzimidazoles with aryl isocyanates as building blocks in the presence of a base under microwave irradiation. A nucleophilic addition followed by an unprecedented transition-metal-free C(sp²)-N coupling is proposed as a reaction pathway of this green process.