Indium(III) Chloride-Catalyzed Propargylation/Amination/Cycloisomerization Tandem Reaction: One-Pot Synthesis of Highly Substituted Pyrroles from Propargylic Alcohols, 1,3-Dicarbonyl Compounds and Primary Amines

Acid-Catalyzed Multicomponent Rearrangements via 2-((Quinoxalin-3(4H)-on-2-yl)(aryl)methylene)malononitriles, Generated In Situ, for Divergent Synthesis of Pyrroles with Different Substitution Patterns

New three-component domino reactions, providing divergent approaches to multifunctionalized pyrroles with different substitution patterns, have been established (47 examples). In this work, a new rearrangement of quinoxalinones with the participation of the in situ-generated 2-en-1-imine moiety of the substituent at C3 makes it possible to construct two new heterocyclic systems, namely, a benzimidazolone and a pyrrole, simultaneously under one-pot reaction conditions. The reaction is easy to perform simply by mixing three common reactants of acetic acid with heating. Secondary amines or primary alcohols as the third component of the reaction, along with quinoxalin-3(4H)-ones and malononitrile, not only initiate the rearrangement but also are responsible for the nature of substituents at position 5 of the pyrrole ring in the newly formed new biheterocyclic system. The reaction proceeds smoothly and can be finished within 7 h, which makes workup convenient to give up to 97% chemical yields.

InCl3: A Versatile Catalyst for Synthesizing a Broad Spectrum of Heterocycles

This review deals with the recent applications of the indium trichloride (InCl₃) catalyst in the synthesis of a broad spectrum of heterocyclic compounds. Over the years, a number of reviews on the applications of InCl₃-catalyzed organic synthesis have appeared in the literature. It is evident that InCl₃ has emerged as a valuable catalyst for a wide range of organic transformations due to its stability when exposed to moisture and also in an aqueous medium. The most attractive feature of this review is the application of the InCl₃ catalyst for synthesizing bioactive heterocyclic compounds. The study of InCl₃-catalyzed organic reactions has high potential and better intriguing aspects, which are anticipated to originate from this field of research.

Iodine-Catalyzed Regioselective Synthesis of Multisubstiuted Pyrrole Polyheterocycles Free from Rotamers and Keto-Enol Tautomers

A highly regioselective iodine-mediated cascade reaction for the synthesis of multifunctional polyheterocyclic systems is developed by employing 3-(2-oxo-2-arylethylidene)oxindoles and 1,4-benzoxazinone as starting materials. The polyheterocycles are skillfully embraced with oxindole, pyrrole, and coumarin scaffolds, which are well-known for their enriched biological activity. The current approach worked under mild reaction conditions. The reaction afforded a single product, and no rotameric and keto-enol isomeric products are formed. The method is environmentally benign and atom-economical, and the only side product of this reaction is water. This protocol obviates the purification techniques such as column chromatography for the isolation of the products. The products were isolated by decantation of the solvent or by recrystallization. The reaction proceeds through inter- and intramolecular C-C and C-N bond formation.

Propargylation of 1,3-dicarbonyl compounds catalyzed by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone and sodium nitrite in the presence of molecular oxygen and formic acid

The coupling reaction of 1,3-diarylpropyne and 1,3-dicarbonyl compounds using molecular oxygen as a terminal oxidation was developed. Catalyzed by DDQ and NaNO₂ in the presence of HCOOH, the corresponding products were obtained in 37–87% yields.

Recent advances in the synthesis of pyrroles by multicomponent reactions

Pyrrole is one of the most important one-ring heterocycles. The ready availability of suitably substituted and functionalized pyrrole derivatives is essential for the progress of many branches of science, including biology and materials science. Access to this key heterocycle by multicomponent routes is particularly attractive in terms of synthetic efficiency, and also from the environmental point of view. We update here our previous review on this topic by describing the progress made in this area in the period between mid-2009 and the end of 2013.

Bridging homogeneous and heterogeneous catalysis with CAN·SiO2as a solid catalyst for four-component reactions for the synthesis of tetrasubstituted pyrroles

The attractive features of this methodology are newer and greener methods, simple procedures, reusability and high efficiency of the catalyst and easy workability.

Metal-catalyzed formation of 1,3-cyclohexadienes: a catalyst-dependent reaction

A metal-dependent and complementary catalytic method to synthesize the cyclohexadienes has been developed. When gold or indium salts were used as catalysts, 1,3-cyclohexadiene (1,3-CHD) could be obtained; when Cu(OTf)₂ was used as the catalyst, however, another isomer 2,4-cyclohexadiene (2,4-CHD) was furnished instead.

Iodine catalyzed one-pot synthesis of highly substituted N-methyl pyrroles via [3 + 2] annulation and their in vitro evaluation as antibacterial agents

A new class of highly substituted pyrroles have been synthesized via a simple, fast, and efficient method using environmentally friendly iodine catalyzed [3 + 2] annulation.

A mild and efficient AgSbF6-catalyzed synthesis of fully substituted pyrroles through a sequential propargylation/amination/cycloisomerization reaction

Development of an efficient synthesis of fully substituted pyrroles via a sequential as a catalyst. The propargylation/amination/cycloisomerization was accomplished using AgSbF₆ one-pot three-component reaction of propargylic alcohols, 1,3-dicarbonyl compounds, and primary amines proceeds at a mild temperature, which prevents the formation of furan by-product. The reaction was also successfully applied to the more basic aliphatic amines with the addition of 1.1 eq. of acetic acid.

Acid-catalyzed domino reactions of tetraarylbut-2-yne-1,4-diols. Synthesis of conjugated indenes and inden-2-ones

The reaction of tetraarylbut-2-yne-1,4-diols with electron-rich aromatic compounds at room temperature, under p-TsOH catalysis, affords substituted polycyclic aromatic indene derivatives through a domino reaction involving the formation of a cationic allenylium intermediate. This species can undergo a series of competitive intramolecular cascade reactions, leading to a conjugated inden-2-one. This simple method allows the efficient synthesis of substituted indenes and inden-2-ones, in two steps, from aromatic ketones.

One-pot synthesis of polysubstituted 3-acylpyrroles by cooperative catalysis

Polysubstituted 3-acylpyrroles were synthesized from readily available unsaturated ketones and N-substituted propargylated amines via an aza-Michael/alkyne carbocyclization cascade followed by oxidation in one pot.

Iron-catalyzed synthesis of polysubstituted pyrroles via [4C+1N] cyclization of 4-acetylenic ketones with primary amines

A highly efficient iron-catalyzed approach to polysubstituted pyrroles has been developed through the [4C+1N] cyclization of 4-acetylenic ketones with primary amines, leading to the synthesis of a variety of tetra- and fully-substituted pyrroles as well as fused pyrrole derivatives in good to excellent yields.