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

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

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

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

Unprecedented Biomimetic Homodimerization of Oroidin and Clathrodin Marine Metabolites in the Presence of HMPA or Phosphonate Salt Tweezers

The first biomimetic homodimerization of oroidin and clathrodin was effected in the presence HMPA and diphosphonate salts, strong guanidinium and amide chelating agents. The intermolecular associations probably interfere with the entropically and kinetically favored intramolecular cyclizations. Use of oroidin·¹/₂HCl salt or clathrodin·¹/₂HCl was indicative in the presence of the ambident nucleophilic and electrophilic tautomers of the 2-aminoimidazolic oroidin and clathrodin precursors. Surprisingly, the homodimerization of oroidin led to the nagelamide D skeleton, while the homodimerization of clathrodin gave the benzene para-symmetrical structure <b>19</b>. The common process was rationalized from tautomeric precursors <b>I</b> and <b>III</b>

Concise synthesis of Didebromohamacanthin A and Demethylaplysinopsine: Addition of Ethylenediamine and Guanidine Derivatives to the Pyrrole-Amino Acid Diketopiperazines in Oxidative Conditions

Oxidative nucleophilic addition of ethylenediamine and guanidine derivatives to pyrrole-amino acid diketopiperazines was shown to provide substituted 5,6-dihydro-2­(1<i>H</i>)-piperazinones, quinoxalinones, and 2-aminoimidazolones. On the basis of this methodology, a concise approach to natural products didebromohamacanthin A and demethylaplysinopsine has been demonstrated