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During the past few decades, carbonylative heterocyclic chemistry have acquired a significant chemical alteration for both academic as well as industrial research. Carbonylative heterocycles are commonly used in organic synthesis and fine chemicals preparation. Introduction of carbonyl group can surge the carbon number of parent molecules in the carbonylation reaction. Herein, we have summarized the main developments achieved on rhodium catalyst from last 20 years in the area of carbonylative heterocyclic synthesis. [ABSTRACT FROM AUTHOR]

Substituted 2‐alkyl‐benzimidazoles were synthesized from benzene‐1,2‐diamine and tertiary amines as alkylating agent under polystyrene supported rhodium (Rh@PS) nanoparticles (NPs) catalyzed conditions. The heterogeneous rhodium catalyst was applied first time for the synthesis of 2‐alkyl‐benzimidazoles. The reaction followed through oxidation of alkylamines, transamination, and oxidative cyclisation with benzene‐1,2‐diamines for the corresponding products synthesis with good yields. The process is applicable for vast substrate scope, several functional groups are tolerable, and the Rh@PS catalyst is recyclable up to four cycles without significant loss in catalytic activity. [ABSTRACT FROM AUTHOR]

An effective and stable polystyrene supported rhodium (Rh@PS) nano‐catalyst has been synthesized by following reduction‐deposition approach and applied for the selective benzimidazoles synthesis from 1,2‐phenylenediamines and ethanol/methanol as C2H3/CH source. The ethanol/methanol in the presence of trace amounts of aerobic oxygen under Rh@PS catalysed condition, first participated in oxidation of alcohol followed by consecutive condensation, cyclization and hydrogen elimination reactions with 1,2‐phenylenediamine gave the desired products in good yields. The Rh@PS catalyst in a single system performed both oxidation and reduction reactions in a selective/specific manner and applied for large substrate scope. Easy recovery, handling, stability, recyclability of the catalyst and less chance of metal contamination with the products are the added advantages of the process. [ABSTRACT FROM AUTHOR]

Abstract: A facile reduction reaction of nitroarenes, aryl carbonyls and aryl/benzyl sulfoxides was performed under polystyrene supported rhodium (Rh@PS) catalyzed conditions using ethanol/methanol as in situ hydrogen source. The catalyst Rh@PS played a pivotal role in the oxidation of ethanol/methanol in the presence of traces of aerial oxygen and base to produce hydrogen gas, enough for further reduction reaction. Transmission electron microscopy (TEM) analysis indicated that the average particle size of the Rh nanoparticles (NPs) lies between 2–3 nm; this is responsible for its high catalytic activity. The advantages of Rh@PS are its catalytic activity, easy preparation, recovery, recyclability for several runs, and low metal leaching during reaction. [ABSTRACT FROM AUTHOR]

Polystyrene-supported rhodium(0) (Rh@PS) nanoparticles (NPs) as a heterogeneous catalyst have been used for the synthesis of monocyclic 3,5-disubstituted cyclopent-2-enones from terminal alkynes and oxalic acid as the in situ C1 source following an intermolecular [2+2+1]-reductive carbonylative cyclization (RCC) reaction. Oxalic acid in the presence of Rh@PS catalyst plays a dual role by acting as CO source and reducing agent (H2) which makes the process feasible for the desired product synthesis. The ionic interaction of oxalic acid to the PS surface of Rh@PS helps to maintain the close vicinity and fruitful interaction with substrates and catalyst required for product formation. [ABSTRACT FROM AUTHOR]

A very unusual role of polystyrene stabilized rhodium (Rh@PS) nanoparticles as a supported catalyst is described for “reverse-esterification” of ethanol with benzyl/alkyl alcohols or aldehydes. Faster and selective oxidation of ethanol to acetaldehyde and H2 under Rh@PS catalyzed conditions which restricted further oxidation of benzyl/alkyl alcohols and their in situ reaction gave the corresponding acetate esters following the dehydrogenative-coupling approach. A hitherto redox dehydrogenative-coupling of ethanol and aldehydes has also been explored for the same acetate ester synthesis under Rh@PS catalyzed conditions. [ABSTRACT FROM AUTHOR]

Abstract: A Solid-supported rhodium(0) (SS-Rh) catalyst has been developed and applied for the chemo- and regio-selective reduction of nitroarenes functionalized with C C multiple bonds and dinitroarenes to their corresponding amines respectively using hydrazine hydrate (N2H4·H2O) as a reducing source under mild microwave irradiation (MWI) conditions. The present methodology also shows excellent compatibility with a broad range of structurally diverse reducible functional groups. The catalyst can be recovered by simple filtration and reused for 13 cycles with consistent activity hence reduces the cost of the catalyst assertively. [Copyright &y& Elsevier]