Nitro-Methyl Redox Coupling: Efficient Approach to 2‑Hetarylbenzothiazoles from 2‑Halonitroarene, Methylhetarene, and Elemental Sulfur

A simple, straightforward, and atom economic approach to 2-hetarylbenzothiazoles starting from 2-halonitroarene, methylhetarene, and elemental sulfur under mild conditions is described. The method is highlighted by the direct redox nitro-methyl reaction for carbon–nitrogen bond formation without an added oxidizing or reducing agent

A Simple and Straightforward Approach to Quinoxalines by Iron/Sulfur-Catalyzed Redox Condensation of <i>o</i>‑Nitroanilines and Phenethylamines

<i>In situ</i> generated iron sulfide from elemental sulfur and ferric chloride was found to be a highly efficient catalyst for the redox condensation cascade reaction between <i>o</i>-nitroanilines and 2-arylethylamines. This method constitutes a new atom-, step-, and redox-economical route to 2-arylquinoxalines

Efficient and Selective Multicomponent Oxidative Coupling of Two Different Aliphatic Primary Amines into Thioamides by Elemental Sulfur

An efficient and selective multicomponent oxidative coupling of two different aliphatic primary amines into thioamides by elemental sulfur under solvent-free conditions has been developed

Iron Sulfide Catalyzed Redox/Condensation Cascade Reaction between 2‑Amino/Hydroxy Nitrobenzenes and Activated Methyl Groups: A Straightforward Atom Economical Approach to 2‑Hetaryl-benzimidazoles and -benzoxazoles

Iron sulfide generated <i>in situ</i> from elemental sulfur and iron was found to be highly efficient in catalyzing a redox/condensation cascade reaction between 2-amino/hydroxy nitrobenzenes and activated methyl groups. This method represents a straightforward and highly atom economical approach to 2-hetaryl-benzimidazoles and -benzoxazoles

Cobalt- and Iron-Catalyzed Redox Condensation of <i>o</i>‑Substituted Nitrobenzenes with Alkylamines: A Step- and Redox-Economical Synthesis of Diazaheterocycles

A wide variety of functionalized 2-aryl benzimidazoles can be prepared by a solvent-free cobalt- or iron-catalyzed redox condensation of 2-nitroanilines and benzylamines. The cascade including benzylamine oxidation, nitro reduction, condensation, and aromatization occurs without any added reducing or oxidizing agent. The method can be extended to other alkylamines as reducing components or 2-nitrobenzamides as oxidizing components when using an iron/sulfur catalyst to afford various diazaheterocycles

Benzazoles from Aliphatic Amines and <i>o</i>‑Amino/Mercaptan/Hydroxyanilines: Elemental Sulfur as a Highly Efficient and Traceless Oxidizing Agent

A novel remarkably simple solvent-free and catalyst-free synthesis of benzazoles from alkylamines and <i>o</i>-hydroxy/amino/mercaptan anilines using elemental sulfur as traceless oxidizing agent has been developed

Elements as Direct Feedstocks for Organic Synthesis: Fe/I₂/O₂ for Diamination of 2‑Cyclohexenones with 2‑Aminopyrimidine and 2‑Aminopyridines

Elements as feedstocks for organic synthesis, the trio of metallic iron, molecular iodine, and dioxygen, were found to be an excellent tool for oxidative regioselective diamination of conjugated enones with 2-aminopyrimidine (a guanidine surrogate) and 2-aminopyridines leading to unaromatized coupled products in moderate to good yields

Reaction of Quinones and Guanidine Derivatives: Simple Access to Bis-2-aminobenzimidazole Moiety of Benzosceptrin and Other Benzazole Motifs

A new strategy for the synthesis of 2-aminobenzimidazol-6-ols via a reaction of quinones with guanidine derivatives is reported. Sequential application of this methodology provided a simple access to the first benzosceptrin analogue bearing a bis-2-aminoimidazole moiety. A concomitant addition of two guanidines to the naphtho­[1′,2′:4,5]­imidazo­[1,2-<i>a</i>]­pyrimidine-5,6-dione, which includes the redox neutral debenzylation and guanidine-assisted cleavage of the 2-aminopyrimidine part resulted in the synthesis of the free challenging contiguous bis-2-aminoimidazole moiety of benzosceprins in one step

Boric Acid: A Highly Efficient Catalyst for Transamidation of Carboxamides with Amines

A novel method of transamidation of carboxamides with amines using catalytic amounts of readily available boric acid under solvent-free conditions has been developed. The scope of the methodology has been demonstrated with (i) primary, secondary, and tertiary amides and phthalimide and (ii) aliphatic, aromatic, cyclic, acyclic, primary, and secondary amines

DABCO-Catalyzed DMSO-Promoted Sulfurative 1,2-Diamination of Phenylacetylenes with Elemental Sulfur and <i>o</i>‑Phenylenediamines: Access to Quinoxaline-2-thiones

The oxidative amination of alkynes typically requires transition metal catalysts and strong oxidants. Herein, we alternatively utilize DABCO as a sulfur-activating catalyst to achieve the sulfurative 1,2-diamination of phenylacetylenes with elemental sulfur and o-phenylenediamines. DMSO was found to be particularly suitable for use as a terminal oxidant for this three-component process. A mechanistic study has shown that this cascade reaction is triggered by the addition of active sulfur species to the triple bond of phenylacetylenes