Employing TosMIC as a C1N1 “Two-Atom Synthon” in Imidazole Synthesis by Neighboring Group Assistance Strategy

N-Benzylhydroxylamine as a novel synthetic block in "C1N1" embedding reaction via α-C(sp3)-H activation strategy

A novel process using N-benzylhydroxylamine hydrochloride as a "C1N1 synthon" in [2+2+1] cyclization for the construction of 1,2,5-trisubstituted imidazoles has been described for the first time. The key to realizing this process lies in capturing arylamines by in situ generated novel acyl ketonitrone intermediates. Subsequent tautomerization activates the α-C(sp3)-H of N-benzylhydroxylamines, and thus breaks through its inherent reaction mode and achieves N, α-C site-selective cyclization. Furthermore, this method enables scale-up synthesis and late-stage modification of complex molecules.

Cu(II)-Mediated Sulfonylation of (Hetero)arenes with TosMIC Using Monodentate Directing Groups

Monodentate chelation-assisted direct ortho-C-H sulfonylation of (hetero)arenes using TosMIC as the novel sulfonylating reagent has been developed. A broad range of substrates, including indolines, indoles, 2-phenylpyridines, and others were well tolerated to afford the corresponding products in moderate to good yields. Mechanistic studies revealed that the sulfonyl radical might be involved. Inspired by the above discovery, preliminary para-C-H sulfonylation of naphthalene substrate was also successfully realized. The current protocol featured with cheap metal catalysis, good functional group compatibility, and operational convenience.

Synthesis of 4-sulfonyl-1,7-diesters via K2CO3-mediated alkylative debenzoylation of α-sulfonyl o-hydroxyacetophenones with acrylates

The synthesis of 4-sulfonyl-1,7-diesters was well developed, under open-vessel conditions, by K2CO3-mediated double alkylation of α-sulfonyl o-hydroxyacetophenones with acrylates and tandem debenzoylation of the resulting α,α-disubstituted o-hydroxyacetophenones. A plausible mechanism is proposed and discussed here. This high-yielding protocol provides a highly effective intermolecular alkylation and intramolecular debenzoylation via the formation of two carbon-carbon (C-C) single bonds and the cleavage of a carbon-carbon (C-C) single bond.

Copper-Catalyzed Chemodivergent Synthesis of Oxazoles and Imidazolidones by Selective C-O/C-N Cyclization

Efficient synthesis of phenylalanine-derived oxazoles and imidazolidones can be achieved by copper-catalyzed reactions that are controlled by directing groups and proceed by selective C-O or C-N coupling. This strategy employs inexpensive commercial copper catalysts and readily available starting materials. It uses a convenient reaction procedure and provides a reliable approach to the versatile and flexible assembly of heterocyclic building blocks.

Pummerer-like Rearrangement Induced Cascade Reactions: Synthesis of Highly Functionalized Imidazoles

Imidazoles are among the most important pharmacophores in medicinal chemistry. Herein we report a tandem protocol for the synthesis of highly substituted imidazoles through Pummerer-like rearrangement induced cascade reactions including two carbon-nitrogen bond formations, and concomitant aromatization under mild reaction conditions. This procedure gives imidazole derivatives bearing numerous functional groups and could be used for modifying natural products as well as pharmaceuticals.

Synthesis of Fully Substituted 5-(o-Hydroxybenzoyl)imidazoles via Iodine-Promoted Domino Reaction of Aurones with Amidines

An iodine-promoted domino reaction of aurones with amidines has been successfully explored. The reaction proceeds in a consecutive manner containing Michael addition, iodination, cyclization from intramolecular nucleophilic substitution, and dehydrogenative aromatization from spiro ring opening. Following this novel strategy, a variety of 1,2,4-trisubstituted 5-(o-hydroxybenzoyl)imidazoles were efficiently synthesized in moderate to good yields from readily available starting materials. A plausible mechanism has been proposed.

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.

I2-Mediated [3 + 2] annulation of methyl-azaarenes with alkyl 2-isocyanoacetates or amino acid ester hydrochlorides: selective synthesis of iodine-functionalized and non-iodine-functionalized fused imidazoles

An I2-mediated [3 + 2] annulation of methyl-azaarenes with alkyl 2-isocyanoacetates or amino acid ester hydrochlorides has been demonstrated. This strategy involves the C≡N cleavage of isocyanides and can selectively...

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.

Fe(III)-Catalyzed N-Amidomethylation of Secondary and Primary Anilines with TosMIC

A Fe(III)-catalyzed N-amidomethylation of secondary and primary anilines with p-toluenesulfonylmethyl isocyanide (TosMIC) in water is described. TosMIC plays dual roles as the source of methylene as well as an amidating reagent to form α-amino amides in this multicomponent reaction. The combination of TosMIC and other isocyanides was also investigated to give the desired products in acceptable yields. The current protocol features use of iron catalyst and nontoxic media, broad substrate scope, mild conditions, and operational simplicity.

I2/CuCl2-Copromoted Formal [4 + 1 + 1] Cyclization of Methyl Ketones, 2-Aminobenzonitriles, and Ammonium Acetate: Direct Access to 2-Acyl-4-aminoquinazolines

We herein report an I₂/CuCl₂-copromoted diamination of C(sp³)-H bonds for the preparation of 2-acyl-4-aminoquinazolines from methyl ketones, 2-aminobenzonitriles, and ammonium acetate. This reaction features operational simplicity, commercially available substrates, mild reaction conditions, and good functional group compatibility. Mechanistic studies indicate that CuCl₂ plays a pivotal role in this transformation. This study uses a methyl group as a novel input to construct 2-acyl-4-aminoquinazoline derivatives for the first time.

Iron-Mediated Selective Sulfonylmethylation of Aniline Derivatives with p-Toluenesulfonylmethyl Isocyanide (TosMIC)

An iron-mediated highly selective C-H sulfonylmethylation of aniline derivatives with p-toluenesulfonylmethyl isocyanide in a mixture solvent of H₂O and PEG₄₀₀ under an Ar atmosphere has been realized. This transformation proceeds with operational convenience, use of earth-abundant metal catalyst and nontoxic media, broad substrate scope, and good functional group tolerance. The current methodology could be applied to the regioselective C-H sulfonylmethylation of indolines, tetrahydroquinolines, and tertiary anilines.

Palladium catalyzed annulation of 2-iodobiphenyl with a non-terminal alkene enabled by neighboring group assistance

In this work, an efficient palladium catalyzed annulation of 2-iodobiphenyl with a non-terminal alkene was developed. The key factor in this transformation was the formation of a highly reactive oxo-palladacycle intermediate, which was enabled by a neighboring hydroxyl group, and remarkably restrained the β-H elimination process. Mechanistically, control experiments demonstrated that the hydroxyl group may act as an anionic ligand, which was irreplaceable in this reaction. This transformation presented good reactivity and selectivity, and no simple Heck coupling products were detected for all of the explored substrates.

Reactions involving aryl methyl ketone and molecular iodine: a powerful tool in the one-pot synthesis of heterocycles

The preparation of heterocyclic compounds has attracted great attention in organic chemistry because of their extensive application in the field of bioactive molecules, materials science, and natural products.

Palladium-Catalyzed Imidoylation-Triggered [2 + 2 + 1] Cyclization of Internal Alkyne with Isocyanides

In this work, a palladium-catalyzed [2 + 2 + 1] cyclization of internal alkynes with double isocyanides is described. This facile procedure is efficient for synthesizing various pyrrolo[3,2-c]quinolin-2-amines. The reaction worked well with a broad reaction scope. In the process, it is believed that sequential double isocyanide insertion, 6-exo-dig cyclization of alkyne, and addition of an imino group are involved.

Sulfoxide Reduction/C(sp3)-S Metathesis Cascade in Ionic Liquid

A sulfoxide reduction/C-S bond metathesis cascade between sulfoxides and alkyl bromides has been developed to access high-value sulfides without the use of any catalysts or bases. In this cascade, classical Kornblum oxidation is employed to reduce sulfoxides with alkyl bromides in ionic liquid. This protocol features high functional tolerance, mild conditions, promising scalability, and sustainable solvents.

Recent advances in the synthesis of imidazoles

The review highlights the recent advances (2018-present) in the regiocontrolled synthesis of substituted imidazoles. These heterocycles are key components to functional molecules that are used in a variety of everyday applications. An emphasis has been placed on the bonds constructed during the formation of the imidazole. The utility of these methodologies based around the functional group compatibility of the process and resultant substitution patterns around the ring are described, including discussion of scope and limitations, reaction mechanisms and future challenges.

[3+1+1] type cyclization of ClCF2COONa for the assembly of imidazoles and tetrazoles via in situ generated isocyanides

A facile synthesis of imidazoles and tetrazoles via [3+1+1] type cyclization of ClCF₂COONa is developed.