Supported Pd−Au bimetallic catalysts (BMCs) have attracted remarkable research interest because they can efficiently execute various important organic transformations. The major concern for launching Pd−Au bimetallic catalysis is either to perform the reaction with good atom economy under low catalyst/ metal loading or to introduce a reaction, which cannot be performed by its monometallic variants. The supports being applied for Pd−Au alloy also have been examined for their crucial role to perform a particular reaction accredited to combined synergistic effects in the catalyst. The optimized tuning between the catalyst support and the Pd/Au ratio always have been a deciding key factor for selectivity, stability, and activity of these catalysts as suggested by various mechanistic studies. Herein, we have summarized the recent advances in supported Pd−Au BMCs in terms of design strategies, characterizations for deep insight mechanistic study during the reaction course. This Review begins with a brief history and adopted methods for preparation of these catalysts followed by categorization of supporting material being applied either directly or after modification. Furthermore, quick glances of catalyst characterization, effects on conversion and selectivity, catalyst activation, and deactivation under the studied reaction parameters for respective organic transformations also have been included in the above-mentioned sections. The main purpose of catalyst development is to accomplish easy access of tedious reactions with good conversion rate and selectivity toward desired product. Therefore, in view of the application part for Pd−Au BMCs, we have tried to cover all basic and important organic reactions along with their substrate scope range and mechanistic studies. This present Review could be really useful for researchers working in this dimension via providing them a clear catalyst design idea, preparation method, support selection strategy, and right substrate screening for carrying out the targeted synthetic transformation.

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The polystyrene supported palladium-gold (PdÀ Au@PS) catalyst was prepared and well characterized by HR-TEM, EDX, Elemental Mapping, XPS and P-XRD analysis. The PdÀ Au@PS NPs displayed the superior catalytic activity than their monometallic forms. First time, the catalyst was applied for methylthioesterification reaction of aryl iodides with oxalic acid and DMSO as in situ carbon monoxide (CO) and methyl mercaptan (CH 3 SH) precursor. Yet, there is no report available where DMSO has been applied as CH 3 SH source for methylthioester synthesis. The CH 3 SH and CO are likely to poison the metal catalyst whereas in PdÀ Au@PS catalyst, the beneficial inter-electronic interactions between Pd and Au metals makes the catalyst highly reactive, poisoning resistant and recyclable during the transformation. Moreover, the developed protocol exhibits excellent functional group tolerance for various aryl iodides to delivered the desired products in moderate to very good yields.

An efficient and straightforward approach has been demonstrated for 2-aryl quinazolinones synthesis from 2-iodoacetanilides using ammonium carbamate/ammonium carbonate and oxalic acid under heterogeneous Pd/C catalyzed conditions. Herein, we have carried out the reactions employing oxalic acid and ammonium carbamate or ammonium carbonate as two gaseous precursors i. e. CO and NH 3 respectively for the synthesis of desired quinazolinones in appreciable yields. The protocol followed cascade aminocarbonylation and cyclization under optimized reaction conditions. The protocol exhibited wide functional group tolerance under set reaction conditions and delivered the respective 2-aryl quinazolinones with great diversity. The heterogeneous Pd/C catalyst was found to be recyclable up to four consecutive runs without significant decrease in catalytic activity.

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Herein, we demonstrated heterogeneous and recyclable polystyrene-supported palladium (Pd@PS) nanoparticles (NPs) catalyzed tandem addition and intramolecular aminocarbonylative cyclization approach for the synthesis of potentially bioactive 2-(alkylamino/amino)-3-arylquinazolin-4(3H)-one analogues from 2-iodophenylcarbodiimides employing amines as nucleophiles and oxalic acid as an ex-situ CO alternative. Various cyclic/acyclic primary and secondary amines were employed and selectively produced substituted 2-(alkylamino)-3-arylquinazolin-4(3H)-ones in good to excellent yields. In addition, we extended the developed strategy to fix two ammonium carbamate and oxalic acid as gaseous NH 3 and CO sources respectively, for the synthesis of 2amino-3-arylquinazolin-4(3H)-one derivatives. Furthermore, gram scale applicability, diverse substrate scope and high recyclability of the Pd@PS catalyst were the major achievements of the developed protocol.

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