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Prasenjit Ghosh - One of the best experts on this subject based on the ideXlab platform.
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One-Pot Tandem Hiyama Alkynylation/Cyclizations by Palladium(II) Acyclic Diaminocarbene (ADC) Complexes Yielding Biologically Relevant Benzofuran Scaffolds.
ACS omega, 2018Co-Authors: Chandan Singh, A. P. Prakasham, Manoj Kumar Gangwar, Ray J. Butcher, Prasenjit GhoshAbstract:A series of palladium acyclic diaminocarbene (ADC) complexes of the type cis-[(R1NH)(R2)methylidene]PdCl2(CNR1) [R1 = 2,4,6-(CH3)3C6H2: R2 = NC5H10 (2); NC4H8 (3); NC4H8O (4)] were used not only to perform the Csp2–Csp Hiyama Coupling between aryl iodide and triethoxysilylalkynes but also to subsequently carry out the one-pot tandem Hiyama alkynylation/cyclization reaction between 2-iodophenol and triethoxysilylalkynes, giving a convenient time-efficient access to the biologically relevant benzofuran compounds. The palladium ADC complexes (2–4) were conveniently synthesized by the nucleophilic addition of secondary amines, namely, piperidine, pyrrolidine, and morpholine on the cis-{(2,4,6-(CH3)3C6H2)NC}2PdCl2 in moderate yields (ca. 61–66%).
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One-Pot Tandem Hiyama Alkynylation/Cyclizations by Palladium(II) Acyclic Diaminocarbene (ADC) Complexes Yielding Biologically Relevant Benzofuran Scaffolds
2018Co-Authors: Chandan Singh, A. P. Prakasham, Manoj Kumar Gangwar, Ray J. Butcher, Prasenjit GhoshAbstract:A series of palladium acyclic diaminocarbene (ADC) complexes of the type cis-[(R1NH)(R2)methylidene]PdCl2(CNR1) [R1 = 2,4,6-(CH3)3C6H2: R2 = NC5H10 (2); NC4H8 (3); NC4H8O (4)] were used not only to perform the Csp2–Csp Hiyama Coupling between aryl iodide and triethoxysilylalkynes but also to subsequently carry out the one-pot tandem Hiyama alkynylation/cyclization reaction between 2-iodophenol and triethoxysilylalkynes, giving a convenient time-efficient access to the biologically relevant benzofuran compounds. The palladium ADC complexes (2–4) were conveniently synthesized by the nucleophilic addition of secondary amines, namely, piperidine, pyrrolidine, and morpholine on the cis-{(2,4,6-(CH3)3C6H2)NC}2PdCl2 in moderate yields (ca. 61–66%)
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fluoride free Hiyama Coupling by palladium abnormal n heterocyclic carbene complexes
Dalton Transactions, 2015Co-Authors: Sudipta Modak, Manoj Kumar Gangwar, Ray J. Butcher, Mitta Nageswar Rao, Mahesh Madasu, Alok Ch Kalita, Vincent Dorcet, Mayuri Arun Shejale, Prasenjit GhoshAbstract:A series of palladium complexes of the abnormal N-heterocyclic carbene ligands of the type (a-NHC)PdI2(L) [L = NC5H5(1–3)b and PPh3(1–3)c] effectively catalyzed the Hiyama Coupling of aryl bromides and iodides with PhSi(OMe)3 under the highly desired fluoride-free conditions. Interestingly enough, the pyridine based trans-(1–3)b complexes and a PPh3 derived cis-3c complex exhibited higher yields than the related PPh3 derived trans-(1–2)c complexes. The superior performances of the pyridine based trans-(1–3)b complexes and the PPh3 derived cis-3c complex have been correlated to a tighter binding of the a-NHC ligand to the palladium center in these complexes, leading to a greater (a-NHC) ligand influence on the metal center partaking in the catalysis
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fluoride free Hiyama and copper and amine free sonogashira Coupling in air in a mixed aqueous medium by a series of peppsi themed precatalysts
European Journal of Inorganic Chemistry, 2009Co-Authors: Chandrakanta Dash, Mobin M Shaikh, Prasenjit GhoshAbstract:A new series of robust, user-friendly, and highly active PEPPSI-themed (pyridine-enhanced precatalyst preparation, stabilization and initiation) (NHC)PdX2(pyridine)-type (X = Cl, Br) precatalysts of C4–C5 saturated imidazole- (1–4) and triazole-based (5 and 6) N-heterocyclic carbenes for the Hiyama and Sonogashira Couplings under amenable conditions are reported. Specifically 1–6 efficiently catalyze the fluoride-free Hiyama Coupling of aryl halides with PhSi(OMe)3 and CH2=CHSi(OMe)3 in air in the presence of NaOH as a base in a mixed aqueous medium (dioxane/H2O, 2:1 v/v). Along the same lines, these 1–6 precatalysts also promote the Cu-free and amine-free Sonogashira Coupling of aryl bromides and iodides with phenylacetylene in air and in a mixed aqueous medium (DMF/H2O, 3/1 v/v). The complexes 1–6 were synthesized by the direct reaction of the respective imidazolinium and triazolium halide salts with PdCl2 in pyridine in the presence of K2CO3 as a base. DFT studies on the catalytically relevant palladium(0) (NHC)Pd(pyridine) precursors 1a–6a reveal significant donation from the N-heterocyclic carbene lone pair onto the unfilled σ* orbital of the trans Pd–pyridine bond. This weakens the Pd-bound “throwaway” pyridine ligand, and its dissociation marks the initiation of the catalytic cycle.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Atsushi Ohtaka - One of the best experts on this subject based on the ideXlab platform.
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detailed mechanism for Hiyama Coupling reaction in water catalyzed by linear polystyrene stabilized pdo nanoparticles
Organometallics, 2017Co-Authors: Akira Sakon, Go Hamasaka, Yasuhiro Uozumi, Tsutomu Shinagawa, Osamu Shimomura, Ryoki Nomura, Atsushi OhtakaAbstract:The catalytic cycle of the Hiyama Coupling reaction in water catalyzed by linear polystyrene-stabilized PdO nanoparticles (PS-PdONPs) was investigated. The formation of 4-methylbiphenyl was confirmed from the reaction of 4-bromotoluene with the catalyst recovered from the reaction of PS-PdONPs with trimethoxyphenylsilane. The catalytic activity of PS-PdONPs significantly diminished upon addition of NaI or poly(4-vinylpyridine). The Hiyama Coupling reaction using PS-PdONPs as a catalyst proceeds through a different mechanism from the commonly accepted one that starts from the oxidative addition of an aryl halide to a Pd(0) species.
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fluoride free Hiyama Coupling reaction catalyzed by linear polystyrene stabilized pdo nanoparticles in water specific reactivity of pdo nanoparticles over pd nanoparticles
Synlett, 2016Co-Authors: Atsushi Ohtaka, Takamasa Kotera, Akira Sakon, Kouhei Ueda, Go Hamasaka, Yasuhiro Uozumi, Tsutomu Shinagawa, Osamu Shimomura, Ryoki NomuraAbstract:Linear polystyrene-stabilized PdO nanoparticles (PS-PdONPs) exhibited high catalytic activity for fluoride-free Hiyama Coupling reaction of aryltrimethoxysilanes with a variety of bromoarenes under air in water. In contrast, no desired Coupling product was obtained from the Hiyama Coupling reaction using linear polystyrene-stabilized Pd nanoparticles (PS-PdNPs) as a catalyst. The different reactivities of PdONPs and PdNPs will be discussed.
Ryoki Nomura - One of the best experts on this subject based on the ideXlab platform.
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detailed mechanism for Hiyama Coupling reaction in water catalyzed by linear polystyrene stabilized pdo nanoparticles
Organometallics, 2017Co-Authors: Akira Sakon, Go Hamasaka, Yasuhiro Uozumi, Tsutomu Shinagawa, Osamu Shimomura, Ryoki Nomura, Atsushi OhtakaAbstract:The catalytic cycle of the Hiyama Coupling reaction in water catalyzed by linear polystyrene-stabilized PdO nanoparticles (PS-PdONPs) was investigated. The formation of 4-methylbiphenyl was confirmed from the reaction of 4-bromotoluene with the catalyst recovered from the reaction of PS-PdONPs with trimethoxyphenylsilane. The catalytic activity of PS-PdONPs significantly diminished upon addition of NaI or poly(4-vinylpyridine). The Hiyama Coupling reaction using PS-PdONPs as a catalyst proceeds through a different mechanism from the commonly accepted one that starts from the oxidative addition of an aryl halide to a Pd(0) species.
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fluoride free Hiyama Coupling reaction catalyzed by linear polystyrene stabilized pdo nanoparticles in water specific reactivity of pdo nanoparticles over pd nanoparticles
Synlett, 2016Co-Authors: Atsushi Ohtaka, Takamasa Kotera, Akira Sakon, Kouhei Ueda, Go Hamasaka, Yasuhiro Uozumi, Tsutomu Shinagawa, Osamu Shimomura, Ryoki NomuraAbstract:Linear polystyrene-stabilized PdO nanoparticles (PS-PdONPs) exhibited high catalytic activity for fluoride-free Hiyama Coupling reaction of aryltrimethoxysilanes with a variety of bromoarenes under air in water. In contrast, no desired Coupling product was obtained from the Hiyama Coupling reaction using linear polystyrene-stabilized Pd nanoparticles (PS-PdNPs) as a catalyst. The different reactivities of PdONPs and PdNPs will be discussed.
Yasuhiro Uozumi - One of the best experts on this subject based on the ideXlab platform.
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the Hiyama cross Coupling reaction at parts per million levels of pd in situ formation of highly active spirosilicates in glycol solvents
Chemistry-an Asian Journal, 2019Co-Authors: Shun Ichii, Go Hamasaka, Yasuhiro UozumiAbstract:A palladium NNC-pincer complex at a 5 mol ppm loading efficiently catalyzed the Hiyama Coupling reaction of aryl bromides with aryl(trialkoxy)silanes in propylene glycol to give the corresponding biaryls in excellent yields. This method was applied to the syntheses of adapalene and a biaryl-type liquid-crystalline compound, as well as to the derivatization of dextromethorphan and norfloxacin. ESI-MS and NMR analyses of the reaction mixture suggested the formation of pentacoordinate spirosilicate intermediates in situ. Preliminary theoretical studies revealed that the glycol-derived silicate intermediates formed in situ are quite reactive silicon reagents in the transmetalation step.
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detailed mechanism for Hiyama Coupling reaction in water catalyzed by linear polystyrene stabilized pdo nanoparticles
Organometallics, 2017Co-Authors: Akira Sakon, Go Hamasaka, Yasuhiro Uozumi, Tsutomu Shinagawa, Osamu Shimomura, Ryoki Nomura, Atsushi OhtakaAbstract:The catalytic cycle of the Hiyama Coupling reaction in water catalyzed by linear polystyrene-stabilized PdO nanoparticles (PS-PdONPs) was investigated. The formation of 4-methylbiphenyl was confirmed from the reaction of 4-bromotoluene with the catalyst recovered from the reaction of PS-PdONPs with trimethoxyphenylsilane. The catalytic activity of PS-PdONPs significantly diminished upon addition of NaI or poly(4-vinylpyridine). The Hiyama Coupling reaction using PS-PdONPs as a catalyst proceeds through a different mechanism from the commonly accepted one that starts from the oxidative addition of an aryl halide to a Pd(0) species.
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fluoride free Hiyama Coupling reaction catalyzed by linear polystyrene stabilized pdo nanoparticles in water specific reactivity of pdo nanoparticles over pd nanoparticles
Synlett, 2016Co-Authors: Atsushi Ohtaka, Takamasa Kotera, Akira Sakon, Kouhei Ueda, Go Hamasaka, Yasuhiro Uozumi, Tsutomu Shinagawa, Osamu Shimomura, Ryoki NomuraAbstract:Linear polystyrene-stabilized PdO nanoparticles (PS-PdONPs) exhibited high catalytic activity for fluoride-free Hiyama Coupling reaction of aryltrimethoxysilanes with a variety of bromoarenes under air in water. In contrast, no desired Coupling product was obtained from the Hiyama Coupling reaction using linear polystyrene-stabilized Pd nanoparticles (PS-PdNPs) as a catalyst. The different reactivities of PdONPs and PdNPs will be discussed.
Go Hamasaka - One of the best experts on this subject based on the ideXlab platform.
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the Hiyama cross Coupling reaction at parts per million levels of pd in situ formation of highly active spirosilicates in glycol solvents
Chemistry-an Asian Journal, 2019Co-Authors: Shun Ichii, Go Hamasaka, Yasuhiro UozumiAbstract:A palladium NNC-pincer complex at a 5 mol ppm loading efficiently catalyzed the Hiyama Coupling reaction of aryl bromides with aryl(trialkoxy)silanes in propylene glycol to give the corresponding biaryls in excellent yields. This method was applied to the syntheses of adapalene and a biaryl-type liquid-crystalline compound, as well as to the derivatization of dextromethorphan and norfloxacin. ESI-MS and NMR analyses of the reaction mixture suggested the formation of pentacoordinate spirosilicate intermediates in situ. Preliminary theoretical studies revealed that the glycol-derived silicate intermediates formed in situ are quite reactive silicon reagents in the transmetalation step.
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detailed mechanism for Hiyama Coupling reaction in water catalyzed by linear polystyrene stabilized pdo nanoparticles
Organometallics, 2017Co-Authors: Akira Sakon, Go Hamasaka, Yasuhiro Uozumi, Tsutomu Shinagawa, Osamu Shimomura, Ryoki Nomura, Atsushi OhtakaAbstract:The catalytic cycle of the Hiyama Coupling reaction in water catalyzed by linear polystyrene-stabilized PdO nanoparticles (PS-PdONPs) was investigated. The formation of 4-methylbiphenyl was confirmed from the reaction of 4-bromotoluene with the catalyst recovered from the reaction of PS-PdONPs with trimethoxyphenylsilane. The catalytic activity of PS-PdONPs significantly diminished upon addition of NaI or poly(4-vinylpyridine). The Hiyama Coupling reaction using PS-PdONPs as a catalyst proceeds through a different mechanism from the commonly accepted one that starts from the oxidative addition of an aryl halide to a Pd(0) species.
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fluoride free Hiyama Coupling reaction catalyzed by linear polystyrene stabilized pdo nanoparticles in water specific reactivity of pdo nanoparticles over pd nanoparticles
Synlett, 2016Co-Authors: Atsushi Ohtaka, Takamasa Kotera, Akira Sakon, Kouhei Ueda, Go Hamasaka, Yasuhiro Uozumi, Tsutomu Shinagawa, Osamu Shimomura, Ryoki NomuraAbstract:Linear polystyrene-stabilized PdO nanoparticles (PS-PdONPs) exhibited high catalytic activity for fluoride-free Hiyama Coupling reaction of aryltrimethoxysilanes with a variety of bromoarenes under air in water. In contrast, no desired Coupling product was obtained from the Hiyama Coupling reaction using linear polystyrene-stabilized Pd nanoparticles (PS-PdNPs) as a catalyst. The different reactivities of PdONPs and PdNPs will be discussed.