@misc{oai:ir.soken.ac.jp:00003576,
 author = {RAGHU NARTH, Dhital and ラグ　ナータ　, ディタール and RAGHU NARTH, Dhital},
 month = {2016-02-17},
 note = {This thesis describes a new method for the construction of carbon-carbon bond by using gold or gold/palladium alloy bimetallic catalysts under ambient conditions. It involves two projects: 1) dual functions of protective agents such as stabilization of gold nanoclusters and activation of substrate, and 2) anomalous efficacy of bimetallic Au/Pd alloy catalysts for C-X bond activation. 
To explore the dual functions of “protective agents”, in the first project, polyhydroxy matrices such as chitosan and/or starch-stabilized Au nanoclusters are prepared and characterized. Thus, prepared Au nanoclusters catalyzed the oxidative homocoupling of arylboronic acids under ambient conditions in acidic medium. The most remarkable finding regarding this reaction is the homocoupling product is formed in the absence of base which is essentially require to activate the substrate before transmetalation. On the basis of the overall reaction trends, kinetics, and spectroscopic analysis, it was confirmed that the essentially required tetra-coordinated boron species are formed by the reversible binding of hydroxyl moieties of polymer with arylboronic acids. 
In the second project, a series of hydrophilic polymer, poly(N-vinylpyrrolidone) (PVP)-stabilized bimetallic Au/Pd alloy catalysts are prepared by co-reduction approach and the catalysts are characterized using UV-visible, X-ray diffraction, transmission electron microscopy (TEM), scanning TEM (STEM), energy dispersive X-ray and X-ray photoelectron spectroscopy (XPS). Thus, prepared bimetallic catalysts show unusual catalytic activities toward the coupling between chlorobenzoic acid and phenylboronic acid at room temperature under aqueous conditions and give Suzuki-Miyaura-type cross-coupling product and metathesis-type homocoupling of phenylboronic acid. Mechanistic investigation showed that, the reaction likely occurs on the surface of bimetallic catalyst through the new mechanism. The reaction did not proceed in the presence of monometallic Au or Pd nanoclusters. 
The first example of the Ullmann coupling of chloroarene catalyzed by Au/Pd alloy catalysts under ambient conditions using DMF as reducing agent is also demonstrated. Bimetallic Au/Pd nanoclusters show an unexpected trend of activation of C-X bonds toward Ullmann coupling reactions and the order of reactivity is C(aryl)-Cl>C(aryl)-Br>>C(aryl)-I. UV–visible and fluorescence spectra show that aryl iodides are selectively adsorbed to the exposed surfaces of gold clusters, thereby masking active sites for catalysis and acted as strong inhibitors.
The Suzuki-Miyaura coupling reactions of 4-bromobenzoic acid and/or 4-iodobenzoic acid with phenylboronic acid by using series of bimetallic Au/Pd alloy are demonstrated. The coupling reaction between 4-bromobenzoic acid and phenylboronic acid in the presence of Au rich bimetallic Au/Pd nanoclusters occurred on the surface of clusters and gave the Suzuki-Miyaura-type cross-coupling product and metathesis-type homocoupling product through new mechanism. The leaching of Pd occurred by using Pd rich bimetallic Au/Pd nanoclusters and selectively governed the Suzuki-Miyaura cross-coupling product through usual Pd2+/Pd0 cycle. However, in the case coupling between 4-iodobenzoic acid and phenylboronic acid selectively cross-coupling product was observed even by using Au rich bimetallic clusters, which was believed to occur by usual mechanism through leaching of Pd., 総研大甲第1541号},
 title = {Gold and Gold-based Bimetallic Catalysis for Carbon-Carbon Bond Formation},
 year = {}
}