deb Basu

Microwave-assisted Suzuki coupling on a KF–alumina surface: synthesis of polyaryls

Abstract A range of conjugated polyaryls has been synthesized through one-pot microwave assisted palladium-catalyzed consecutive Suzuki coupling reactions on a KF–alumina surface with notable features including rapid reaction times, solvent-free conditions, high yields, atom economic and air-insensitive reactions.

Recent advances in S–S bond formation

Organic compounds possessing S–S bonds, often called disulfides or more specifically disulfanes, have been widely applied in various fields ranging from biochemistry to different industrially important polymers, used as synthetic intermediates in other fine chemicals such as catenanes, rotaxanes, micelles, and also in areas like peptidomimetics, self-assembled monolayers (SAMs) etc. Such versatile applications have steered the development of several new methods for the preparation of organic disulfides. The present review has attempted to comprehensively summarize recent advances in the process of S–S bond formation, highlighting plausible mechanistic considerations, scope and limitations.

Highly effective alternative aryl trihydroxyborate salts for a ligand-free, on-water Suzuki–Miyaura coupling reaction

Aryl trihydroxyborate salts of sodium, an easily accessible and stable alternative source of organoboron species, can efficiently promote Pd-catalyzed ligand-free, on-water Suzuki–Miyaura (SM) coupling reactions at ambient temperature.

Pd/Cu bimetallic nanoparticles embedded in macroporous ion-exchange resins: an excellent heterogeneous catalyst for the Sonogashira reaction

Cationic and macroporous amberlite resins with formate (HCOO−) as the counter anion (ARF) have been used to prepare a new class of heterogeneous Pd/Cu bimetallic composite nanoparticles (NPs) (Pd/Cu–ARF). The physicochemical characteristics of Pd/Cu–ARF were examined with the help of FTIR spectroscopy, X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and atomic absorption spectroscopy (AAS). XRD and TEM showed the existence of composite NPs made of metallic Pd, PdO and CuO. The TEM analysis revealed fairly uniform distributions of composite NPs of average size ∼4.9 nm. The as-synthesized nanocomposite material (Pd/Cu–ARF) exhibited high catalytic activity in the Sonogashira cross-coupling reaction between aryl iodide and terminal alkynes. Heterogeneity of the catalytic activity was evidenced from different tests (hot-filtration and catalyst-poisoning experiments) and the recycling ability of the catalyst was examined for five consecutive runs without any significant loss of activity.

Silica-promoted facile synthesis of thioesters and thioethers: a highly efficient, reusable and environmentally safe solid support

An efficient, mild and rapid procedure for the acylation and alkylation of aromatic and aliphatic thiols mediated on a silica gel surface at room temperature is described. The protocol allows the protection of thiols under neutral heterogeneous conditions without requiring any bases or Lewis acids, and the silica gel used as the promoter can be recycled for several runs without any loss of activity.

Highly selective N-Alkylation of amines promoted on silica: An efficient and recyclable surface

N-Alkylation of amines suffers from competing over alkylations. At the same time, use of strong base and other harsh conditions greatly limits providing a practical, generalized and selective procedure. Activated silica gel has been found to promote N-alkylations of amines. Here, we studied N-alkylation of amines with various types of alkyl halides, which finally constitute practical, highly selective and eco-friendly conditions for mono- or bis-alkylated amines at ambient temperature with recyclability of silica.

Graphene oxide (GO)-catalyzed multi-component reactions: green synthesis of library of pharmacophore 3-sulfenylimidazo[1,2-a]pyridines

The green carbocatalyst graphene oxide (GO) has been successfully utilized for selective and expedient synthesis of biologically important motifs imidazo[1,2-a]pyridines, and 3-sulfenylimidazo[1,2-a]pyridines via one-pot multi-component reactions (MCR). Diversity in small heterocyclic molecular synthesis has been demonstrated with tolerance of broad range of functional groups establishing the generality of the reaction and as well as demonstrating preparation of libraries of potential pharmacophores. The reactions are believed to proceed via selective and tandem reactions in the presence of GO and NaI (as the additive), and the catalyst GO was found to be easily recoverable and recyclable with appreciable conversions.

Palladium-catalysed amination of halopyridines on a KF-alumina surface

Abstract Palladium-catalysed C–N hetero cross-coupling reactions between bromopyridines and amines (both primary and secondary) can be efficiently performed on a KF-alumina (basic) surface, thus negating the use of strong bases such as sodium tert -butoxide. The reaction conditions are optimised with reference to catalytic systems, solvents and the surface.

Graphene oxide as a carbocatalyst: the first example of a one-pot sequential dehydration–hydrothiolation of secondary aryl alcohols

An efficient and mild one-pot graphene oxide (GO)-catalyzed sequential dehydration–hydrothiolation reaction has been developed for the first time from a mixture of secondary aryl alcohols and thiols. The resulting unsymmetrical thioethers were prepared under metal-free conditions. The catalyst can be reused for five runs with appreciable conversions.

Microwave‐Assisted Copper Promoted N‐Arylation of Amines with Aryl Boronic Acids/Salts on a KF–Alumina Surface

Abstract An experimentally simple microwave‐assisted solvent‐free N‐arylation of primary amines with sodium tetraphenylborate or arylboronic acids, promoted by inexpensive cupric acetate, on the surface of KF–alumina is reported. The reaction is selective for mono‐N‐arylation, and a variety of functional groups are tolerated in the process.