CuI/BF3·Et2O cocatalyzed aerobic dehydrogenative reactions of ketones with benzylamines: facile synthesis of substituted imidazoles

Synthesis of 1-Benzyl-2,4-diarylimidazole through I2/CuI-Catalyzed Cyclization of Benzylamine and Hydrazone

In this paper, we report an innovative method for synthesizing 1-benzyl-2,4-diarylimidazole utilizing 1-phenylethanone-2-(2-pyridinyl) hydrazine and benzylamine, catalyzed by an I2/CuI system. This approach represents a significant departure from traditional methods for synthesizing polysubstituted imidazoles; it employs the I2/CuI catalyst to replace rare metal catalysts, thereby achieving high yields of substitution products (≤85%). This method for the generation of 1,2,4-triimidazole derivatives is characterized by its exceptional chemical selectivity and extensive substrate compatibility.

Electrochemically Induced Synthesis of Imidazoles from Vinyl Azides and Benzyl Amines

An electrochemically induced synthesis of imidazoles from vinyl azides and benzyl amines was developed. A wide range of imidazoles were obtained, with yields of 30 to 64%. The discovered transformation is a multistep process whose main steps include the generation of electrophilic iodine species, 2H-azirine formation from the vinyl azide, followed by its reactions with benzyl amine and with imine generated from benzyl amine. The cyclization and aromatization of the obtained intermediate lead to the target imidazole. The synthesis proceeds under constant current conditions in an undivided cell. Despite possible cathodic reduction of various unsaturated intermediates with C=N bonds, the efficient electrochemically induced synthesis of imidazoles was carried out.

TEMPO mediated oxidative annulation of aryl methyl ketones with amines/ammonium acetate for imidazole synthesis

A facile synthesis of 1H-imidazoles by direct oxidative annulation of aryl methyl ketones and primary amines has been developed in the presence of TEMPO under weakly acidic conditions. By replacing amines with ammonium acetate, 2H-imidazole skeletons were achieved for the first time from ketones. Substrates containing various functional groups, such as alkyl, aryl, naphthyl, halogen (F, Cl, Br, I), nitro, trifluoromethyl, sulfonyl ester, furyl, thienyl, and pyridyl groups, were readily transformed into the desired products. The application potential of this method was verified by the scale-up synthesis and Sonogashira coupling functionalization of imidazoles. Mechanistically, the α-TEMPO-enamine adduct may serve as the key reaction intermediate.

Ketones as strategic building blocks for the synthesis of natural product-inspired compounds

Natural product-inspired compound collections serve as excellent sources for the identification of new bioactive compounds to treat disease. However, such compounds must necessarily be more structurally-enriched than traditional screening compounds, therefore inventive synthetic strategies and reliable methods are needed to prepare them. Amongst the various possible starting materials that could be considered for the synthesis of natural product-inspired compounds, ketones can be especially valuable due to the vast variety of complexity-building synthetic transformations that they can take part in, their high prevalence as commercial building blocks, and relative ease of synthesis. With a view towards developing a unified synthetic strategy for the preparation of next generation bioactive compound collections, this review considers whether ketones could serve as general precursors in this regard, and summarises the opulence of synthetic transformations available for the annulation of natural product ring-systems to ketone starting materials.

Catalytic divergent synthesis of imidazoles via reaction condition-dependent [3 + 2] cyclization of TosMIC

A base-catalyzed divergent synthesis of 1,4,5-trisubstituted or 1,4-disubstituted imidazoles through TosMIC-based [3 + 2] cyclization reaction has been developed.

Direct synthesis of 2,4,5-trisubstituted imidazoles from primary alcohols by diruthenium(ii) catalysts under aerobic conditions

A straightforward synthetic approach to 2,4,5-trisubstituted imidazoles from readily available primary alcohols using arene diruthenium(ii) catalysts has been described.

Synthesis of 1,2,4-Trisubstituted-(1H)-imidazoles through Cu(OTf)2-/I2-Catalyzed C-C Bond Cleavage of Chalcones and Benzylamines

1,2,4-Trisubstituted-(1H)-imidazoles have been synthesized by the Cu(OTf)₂- and I₂-catalyzed unusual C-C bond cleavage of chalcones and benzylamines. After the α,β-unsaturated C-C bond cleavage, the β-portion is eliminated from the reaction. Various aryl- and heteroaryl-substituted chalcones and benzylamines were well tolerated in this unusual transformation to yield the trisubstituted-(1H)-imidazoles.

Tunable Cu(i)-catalyzed site-selective dehydrogenative amination of β,γ-unsaturated hydrazones for divergent synthesis of pyrazol-4-ones and 1,6-dihydropyradazines

A new tunable Cu(i)-catalyzed site-selective dehydrogenative amination of β,γ-unsaturated hydrazones has been established using readily accessible dioxygen as a green oxidant.

Controllable access to multi-substituted imidazoles via palladium(ii)-catalyzed C–C coupling and C–N condensation cascade reactions

A novel and efficient protocol for the controllable synthesis of various di-, tri- and tetra-substituted imidazoles via cascade palladium catalyzed C–C coupling followed by intramolecular C–N bond formation was developed.

Silver-Catalyzed Isocyanide-Isocyanide [3+2] Cross-Cycloaddition Involving 1,2-Group Migration: Efficient Synthesis of Trisubstituted lmidazoles

Imidazole ring is an important five-membered aromatic heterocycle that is widely present in natural products and synthetic molecules. The isocyanide-isocyanide [3+2] cross-cycloaddition reaction constitutes a straightforward method to access imidazoles starting from the easily available chemicals. So far, only three successive reports are known and all lead to the formation of 1,4-disubstituted imidazoles. Here, we report the first isocyanide-isocyanide [3+2] cross-cycloaddition reaction allowing for the formation of 1,4,5-trisubstituted imidazoles under silver catalysis. An unexpected 1,2-migration of sulfonyl, alkoxycaybonyl, and carbamoyl groups took place during the cyclization process that is responsible for the formation of trisubstituted imidazoles. This report displayed a mechanistically novel synthetic method toward a variety of imidazole derivatives, which are otherwise difficult to access by conventional methods.

A facile and efficient method for the synthesis of 1,2,4-trisubstituted imidazoles with enamides and benzylamines

A novel and practical method for the construction of 1,2,4-trisubstituted imidazoles with enamides and benzylamines catalysed by CuBr and I₂ has been developed.

Copper-catalyzed aerobic oxidative coupling: From ketone and diamine to pyrazine

Copper-catalyzed aerobic oxidative C-H/N-H coupling between simple ketones and diamines was developed toward the synthesis of a variety of pyrazines. Various substituted ketones were compatible for this transformation. Preliminary mechanistic investigations indicated that radical species were involved. X-ray absorption fine structure experiments elucidated that the Cu(II) species 5 coordinated by two N atoms at a distance of 2.04 Å and two O atoms at a shorter distance of 1.98 Å was a reactive one for this aerobic oxidative coupling reaction. Density functional theory calculations suggested that the intramolecular coupling of cationic radicals was favorable in this transformation.

Copper catalysed direct amidation of methyl groups with N-H bonds

An efficient copper catalyzed direct aerobic oxidative amidation of methyl groups of azaarylmethanes with N-H bonds producing amides is successfully developed, which can produce primary, secondary and tertiary amides, including those with functional groups. This reaction represents a straightforward method for the preparation of amides from the readily available hydrocarbon starting materials.

Current advances in the synthesis and biological potencies of tri- and tetra-substituted 1H-imidazoles

In this report, we review the current chemistry progress and in particular the synthesis approaches of tri- and tetra-substituted imidazoles.

Formal total synthesis of calothrixin B and its N-benzyl analogues

A formal total synthesis of calothrixin B and its N-benzyl analogues has been reported from (2-chlorophenyl)boronic acid, 8-bromophenanthridine-dione and benzylamines.

I2-catalyzed synthesis of substituted imidazoles from vinyl azides and benzylamines

A novel and efficient I₂-catalyzed oxidative tandem cyclization of simple vinyl azides and benzylamines has been developed for the synthesis of substituted imidazoles.

Bond and small-molecule activation with low-valent nickel complexes

The use of nickel compounds in low oxidation states allowed a variety of useful transformations of interest for academia, industry and in the solution of environmental issues.

Copper-catalyzed aerobic oxidative amination of sp3 C-H bonds: efficient synthesis of 2-hetarylquinazolin-4(3H)-ones

An efficient synthesis of 2-hetarylquinazolin-4(3H)-ones via copper-catalyzed direct aerobic oxidative amination of sp(3)C-H bonds has been developed. This tandem oxidation-amination-cyclization transformation represents a straightforward protocol to prepare 2-hetaryl-substituted quinazolinones from easily available 2-aminobenzamides and (2-azaaryl)methanes.