Ludmila Ermolenko

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.

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 in situ 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.

Three-Component Reaction between Alkynes, Elemental Sulfur, and Aliphatic Amines: A General, Straightforward, and Atom Economical Approach to Thioamides

A general, straightforward, and atom-economical three-component synthesis of thioamides from alkynes, elemental sulfur, and aliphatic amines has been developed.

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.

Cobalt- and Iron-Catalyzed Redox Condensation of o-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.

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.

Concise Access to 2-Aroylbenzothiazoles by Redox Condensation Reaction between o-Halonitrobenzenes, Acetophenones, and Elemental Sulfur

A wide range of 2-aroylbenzothiazoles 3 including some pharmacologically relevant derivatives can be obtained in high yields by simply heating o-halonitrobenzenes 1, acetophenones 2, elemental sulfur, and N-methylmorpholine. This three-component nitro methyl coupling was found to occur in an excellent atom-, step-, and redox-efficient manner in which elemental sulfur played the role of nucleophile building block and redox moderating agent to fulfill electronic requirements of the global reaction.

Hydrogen Bond Organocatalysis of Benzotriazole in Transamidation of Carboxamides with Amines

A new method of transamidation of carboxamides with amines catalyzed by benzotriazole has been developed. INTRODUCTION Amide bonds are ubiquitous in living systems and play a key role in bioorganic and medicinal chemistry. Carboxamide group was found to appear in more than 25% of known drugs. Amide formation is thus one of the most fundamental reactions in organic synthesis. The most common strategy for amide bond formation is the reaction between amines and carboxylic acids in the presence of stoichiometric amounts of activating reagents. For this approach, the first step is the activation of the acid (acid chlorides, acylimidazoles, acylazides, anhydrides, and active esters), followed by aminolysis. Much effort has been made to develop a catalytic direct amidation. Alternatively, transamidation reaction between a carboxamide and an amine is an attractive tool in synthetic organic chemistry. However, uncatalyzed transamidation required in general drastic heating conditions. Different methods utilizing activating reagents or catalysts have been developed with the objective to decrease the reaction temperature. Despite their wide scope, these protocols required at least one of these conditions: (i) energetically favorable systems (ring-opening of four-membered rings; (ii) intramolecular assistance, or both factors); (iii) use of moisture-sensitive and/or activation reagents (up to 2–3 equivalents; borate esters, dialkylformamide dialkyl acetals, AlCl3, AlMe3, HCl). Examples of transamidation from the Stahls group provided an elegant possibility of preparing amides under mild † This paper is dedicated to Prof. Victor Snieckus on the occasion of his 77 birthday. HETEROCYCLES, Vol. 88, No. 1, 2014 403

Molecular Iodine-Catalyzed Aerobic α,β-Diamination of Cyclohexanones with 2-Aminopyrimidine and 2-Aminopyridines.

Molecular iodine is shown to be an excellent catalyst for aerobic oxidative α,β-diamination of cyclohexanones with 2-aminopyrimidine/2-aminopyridines. This α,β-C-H functionalization is remarkable for its simplicity in both substrates and conditions, involving one and a half oxygen molecules and releasing three water molecules as the only byproduct. In addition, the functionalized products including protected 2-aminoimidazoles introduced without aromatization can serve as useful building blocks for natural product synthesis and medicinal chemistry.