The Experts below are selected from a list of 2091 Experts worldwide ranked by ideXlab platform
G Van Koten - One of the best experts on this subject based on the ideXlab platform.
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periphery palladated carbosilane dendrimers synthesis and reactivity of organopalladium ii and iv dendritic complexes crystal structure of pdme c6h4 och2ph 4 bpy bpy 2 2 bipyridine
Organometallics, 1999Co-Authors: Neldes J Hovestad, J L Hoare, J T B H Jastrzebski, Allan J Canty, W J J Smeets, Anthony L Spek, G Van KotenAbstract:A carbosilane dendrimer with 12 peripheral Iodoarene groups, [Si{(CH2)3Si((CH2)3SiMe2(C6H4CH2OC6H4I-4))3}4] (G1-ArI, 9), and the corresponding G0 model compound [Si- {(CH2)3SiMe2(C6H4CH2OC6H4I-4)}4] (G0-ArI, 8) have been prepared from [Si{(CH2)3Si((CH2)3SiMe2(C6H4CH2Br))3}4] (G1-Br, 7) and the corresponding G0 model compound [Si{(CH2)3SiMe2(C6H4CH2Br)}4] (G0-Br, 6). These dendritic species react with [Pd2(dba)3âdba/tmeda] (dba = dibenzylideneacetone, tmeda = N,N,N',N'-tetramethylethylenediamine) to yield the periphery palladated complexes [Si{(CH2)3SiMe2(C6H4CH2O(C6H4-4)PdI(tmeda))}4] (G0-ArPdI(tmeda), 10) and [Si{(CH2)3Si((CH2)3SiMe2(C6H4CH2O(C6H4-4)PdI(tmeda))3}4] (G1-ArPdI(tmeda), 11). Complexes 10 and 11 react with LiMe and 2,2'-bipyridine (bpy) to yield the air-stable [Si- {(CH2)3SiMe2(C6H4CH2OC6H4PdMe(bpy))}4] (G0-PdMe(bpy), 12) and [Si{(CH2)3Si((CH2)3SiMe2(C6H4CH2OC6H4PdMe(bpy)))3}4] (G1-ArPdMe(bpy), 13). Complexes 12 and 13 undergo oxidative addition with benzyl bromide to form species containing Pd(IV) centers. These complexes can undergo subsequent reductive elimination at ambient temperature involving both Me-Ar and Me-CH2Ph coupling on decomposition. Iodoarenes that model the arms of carbosilane-based dendrimers have been synthesized, and procedures have been developed for maximizing yields of organopalladium(II) and -(IV) derivatives of the Iodoarenes as part of a program directed toward the isolation and study of organopalladium functionalized dendrimers. The Iodoarenes RC6H4(CH2OC6H4I-4¢)-4 (R = H (1a), SiMe3 (1b)) were obtained and found to undergo facile oxidative addition to [Pd2(dba)3âdba/tmeda] to form [PdI(Ar)(tmeda)] (2a,b), which react with LiMe to form [PdMe(Ar)(tmeda)] (3a,b). Bpy displaces tmeda to form [PdMe(Ar)(bpy)] (4a,b), and the latter complexes undergo oxidative addition with benzyl bromide to form the complexes [PdBrMeAr(CH2Ph)(bpy)] (5a,b). The palladium(IV) complex 5a undergoes facile and clean reductive elimination at ambient temperature in CDCl3 to form the coupling products Me-C6H4(OCH2Ph)-4 (89%), PhCH2-C6H4(OCH2Ph)-4 (9%), and Me-CH2Ph (2%). However, 5b undergoes more complex behavior to form MeC6H4(OCH2C6H4(SiMe3)-4')-4 (87%), Me-CH2Ph (6%), and PhCH2-CH2Ph (7%) together with [PdBr2(bpy)]. The complex [PdMe(C6H4(OCH2Ph)-4)(bpy)] (4a) has been characterized by X-ray diffraction. The asymmetric unit contains two similar but crystallographically independent molecules. Each molecule has square-planar geometry for palladium with the aryl ring tilted by 76.2(4) and 67.1(3)° to the coordination plane, respectively. The crystal examined by X-ray diffraction exhibits significant substitutional disorder at one site: [PdX(C6H4(OCH2Ph)-4)(bpy)] (X ) Me (71%), Cl (29%)).
Akio Saito - One of the best experts on this subject based on the ideXlab platform.
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Iodine(III)-Catalyzed Formal [2 + 2 + 1] Cycloaddition Reaction for Metal-Free Construction of Oxazoles
2017Co-Authors: Takuma Yagyu, Yusuke Takemoto, Akira Yoshimura, Viktor V. Zhdankin, Akio SaitoAbstract:The iodine(III) catalyst, in situ generated from Iodoarene as a precatalyst with m-CPBA and Tf2NH, promoted the metal-free [2 + 2 + 1] cycloaddition-type reactions of alkynes, nitriles, and oxygen atoms for the regioselective formations of 2,4-disubstituted and 2,4,5-trisubstituted oxazole. A first example of iodine catalysis for multicomponent reactions is represented
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catalytic cycloisomerization fluorination sequence of n propargyl amides by Iodoarene hf pyridine selectfluor systems
Asian Journal of Organic Chemistry, 2016Co-Authors: Naoki Asari, Yusuke Takemoto, Yukino Shinomoto, Takuma Yagyu, Akira Yoshimura, Viktor V. Zhdankin, Akio SaitoAbstract:As a first example for metal-free and catalytic fluorinative transformations of alkynes, we developed a cycloisomerization-fluorination sequence of N-propargyl amides catalyzed by iodine(III) species. The iodine(III) catalyst is in situ generated from Iodoarene as a precatalyst with Selectfluor as a fluorinating oxidant in the presence of HF·pyridine.
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Catalytic Cycloisomerization–Fluorination Sequence of N‐Propargyl Amides by Iodoarene/HF⋅Pyridine/Selectfluor Systems
Asian Journal of Organic Chemistry, 2016Co-Authors: Naoki Asari, Yusuke Takemoto, Yukino Shinomoto, Takuma Yagyu, Akira Yoshimura, Viktor V. Zhdankin, Akio SaitoAbstract:As a first example for metal-free and catalytic fluorinative transformations of alkynes, we developed a cycloisomerization-fluorination sequence of N-propargyl amides catalyzed by iodine(III) species. The iodine(III) catalyst is in situ generated from Iodoarene as a precatalyst with Selectfluor as a fluorinating oxidant in the presence of HF·pyridine.
Viktor V. Zhdankin - One of the best experts on this subject based on the ideXlab platform.
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Iodine(III)-Catalyzed Formal [2 + 2 + 1] Cycloaddition Reaction for Metal-Free Construction of Oxazoles
2017Co-Authors: Takuma Yagyu, Yusuke Takemoto, Akira Yoshimura, Viktor V. Zhdankin, Akio SaitoAbstract:The iodine(III) catalyst, in situ generated from Iodoarene as a precatalyst with m-CPBA and Tf2NH, promoted the metal-free [2 + 2 + 1] cycloaddition-type reactions of alkynes, nitriles, and oxygen atoms for the regioselective formations of 2,4-disubstituted and 2,4,5-trisubstituted oxazole. A first example of iodine catalysis for multicomponent reactions is represented
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catalytic cycloisomerization fluorination sequence of n propargyl amides by Iodoarene hf pyridine selectfluor systems
Asian Journal of Organic Chemistry, 2016Co-Authors: Naoki Asari, Yusuke Takemoto, Yukino Shinomoto, Takuma Yagyu, Akira Yoshimura, Viktor V. Zhdankin, Akio SaitoAbstract:As a first example for metal-free and catalytic fluorinative transformations of alkynes, we developed a cycloisomerization-fluorination sequence of N-propargyl amides catalyzed by iodine(III) species. The iodine(III) catalyst is in situ generated from Iodoarene as a precatalyst with Selectfluor as a fluorinating oxidant in the presence of HF·pyridine.
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Catalytic Cycloisomerization–Fluorination Sequence of N‐Propargyl Amides by Iodoarene/HF⋅Pyridine/Selectfluor Systems
Asian Journal of Organic Chemistry, 2016Co-Authors: Naoki Asari, Yusuke Takemoto, Yukino Shinomoto, Takuma Yagyu, Akira Yoshimura, Viktor V. Zhdankin, Akio SaitoAbstract:As a first example for metal-free and catalytic fluorinative transformations of alkynes, we developed a cycloisomerization-fluorination sequence of N-propargyl amides catalyzed by iodine(III) species. The iodine(III) catalyst is in situ generated from Iodoarene as a precatalyst with Selectfluor as a fluorinating oxidant in the presence of HF·pyridine.
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hypervalent iodine catalyzed generation of nitrile oxides from oximes and their cycloaddition with alkenes or alkynes
Organic Letters, 2013Co-Authors: Akira Yoshimura, Kyle R Middleton, Anthony D Todora, Brent J Kastern, Steven R Koski, Andrey V Maskaev, Viktor V. ZhdankinAbstract:Hypervalent iodine catalyzed oxidation of aldoximes using oxone as a terminal oxidant generates nitrile oxides, which react with alkenes and alkynes to give the corresponding isoxazolines and isoxazoles in moderate to good yields. This reaction involves active hypervalent iodine species formed in situ from catalytic Iodoarene and oxone in the presence of hexafluoroisopropanol in aqueous methanol solution.
Igor Larrosa - One of the best experts on this subject based on the ideXlab platform.
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overriding ortho para selectivity via a traceless directing group relay strategy the meta selective arylation of phenols
Journal of the American Chemical Society, 2014Co-Authors: Junfei Luo, Sara Preciado, Igor LarrosaAbstract:The direct functionalization of phenols at the ortho and para position is generally facilitated by the electron-donating nature of the hydroxyl group. Accessing meta-functionalized phenols from the parent phenols, on the other hand, generally requires lengthy synthetic sequences. Here, we report the first methodology for the one-pot direct meta-selective arylation of phenols. This methodology is based on a traceless directing group relay strategy. In this process carbon dioxide is used as a transient directing group which facilitates a palladium catalyzed arylation meta to the phenol hydroxyl group with Iodoarenes. This transformation proceeds with complete meta-selectivity and is compatible with a variety of functional groups both in the phenol and in the Iodoarene coupling partner.
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Overriding Ortho–Para Selectivity via a Traceless Directing Group Relay Strategy: The Meta-Selective Arylation of Phenols
2014Co-Authors: Junfei Luo, Sara Preciado, Igor LarrosaAbstract:The direct functionalization of phenols at the ortho and para position is generally facilitated by the electron-donating nature of the hydroxyl group. Accessing meta-functionalized phenols from the parent phenols, on the other hand, generally requires lengthy synthetic sequences. Here, we report the first methodology for the one-pot direct meta-selective arylation of phenols. This methodology is based on a traceless directing group relay strategy. In this process carbon dioxide is used as a transient directing group which facilitates a palladium catalyzed arylation meta to the phenol hydroxyl group with Iodoarenes. This transformation proceeds with complete meta-selectivity and is compatible with a variety of functional groups both in the phenol and in the Iodoarene coupling partner
Neldes J Hovestad - One of the best experts on this subject based on the ideXlab platform.
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periphery palladated carbosilane dendrimers synthesis and reactivity of organopalladium ii and iv dendritic complexes crystal structure of pdme c6h4 och2ph 4 bpy bpy 2 2 bipyridine
Organometallics, 1999Co-Authors: Neldes J Hovestad, J L Hoare, J T B H Jastrzebski, Allan J Canty, W J J Smeets, Anthony L Spek, G Van KotenAbstract:A carbosilane dendrimer with 12 peripheral Iodoarene groups, [Si{(CH2)3Si((CH2)3SiMe2(C6H4CH2OC6H4I-4))3}4] (G1-ArI, 9), and the corresponding G0 model compound [Si- {(CH2)3SiMe2(C6H4CH2OC6H4I-4)}4] (G0-ArI, 8) have been prepared from [Si{(CH2)3Si((CH2)3SiMe2(C6H4CH2Br))3}4] (G1-Br, 7) and the corresponding G0 model compound [Si{(CH2)3SiMe2(C6H4CH2Br)}4] (G0-Br, 6). These dendritic species react with [Pd2(dba)3âdba/tmeda] (dba = dibenzylideneacetone, tmeda = N,N,N',N'-tetramethylethylenediamine) to yield the periphery palladated complexes [Si{(CH2)3SiMe2(C6H4CH2O(C6H4-4)PdI(tmeda))}4] (G0-ArPdI(tmeda), 10) and [Si{(CH2)3Si((CH2)3SiMe2(C6H4CH2O(C6H4-4)PdI(tmeda))3}4] (G1-ArPdI(tmeda), 11). Complexes 10 and 11 react with LiMe and 2,2'-bipyridine (bpy) to yield the air-stable [Si- {(CH2)3SiMe2(C6H4CH2OC6H4PdMe(bpy))}4] (G0-PdMe(bpy), 12) and [Si{(CH2)3Si((CH2)3SiMe2(C6H4CH2OC6H4PdMe(bpy)))3}4] (G1-ArPdMe(bpy), 13). Complexes 12 and 13 undergo oxidative addition with benzyl bromide to form species containing Pd(IV) centers. These complexes can undergo subsequent reductive elimination at ambient temperature involving both Me-Ar and Me-CH2Ph coupling on decomposition. Iodoarenes that model the arms of carbosilane-based dendrimers have been synthesized, and procedures have been developed for maximizing yields of organopalladium(II) and -(IV) derivatives of the Iodoarenes as part of a program directed toward the isolation and study of organopalladium functionalized dendrimers. The Iodoarenes RC6H4(CH2OC6H4I-4¢)-4 (R = H (1a), SiMe3 (1b)) were obtained and found to undergo facile oxidative addition to [Pd2(dba)3âdba/tmeda] to form [PdI(Ar)(tmeda)] (2a,b), which react with LiMe to form [PdMe(Ar)(tmeda)] (3a,b). Bpy displaces tmeda to form [PdMe(Ar)(bpy)] (4a,b), and the latter complexes undergo oxidative addition with benzyl bromide to form the complexes [PdBrMeAr(CH2Ph)(bpy)] (5a,b). The palladium(IV) complex 5a undergoes facile and clean reductive elimination at ambient temperature in CDCl3 to form the coupling products Me-C6H4(OCH2Ph)-4 (89%), PhCH2-C6H4(OCH2Ph)-4 (9%), and Me-CH2Ph (2%). However, 5b undergoes more complex behavior to form MeC6H4(OCH2C6H4(SiMe3)-4')-4 (87%), Me-CH2Ph (6%), and PhCH2-CH2Ph (7%) together with [PdBr2(bpy)]. The complex [PdMe(C6H4(OCH2Ph)-4)(bpy)] (4a) has been characterized by X-ray diffraction. The asymmetric unit contains two similar but crystallographically independent molecules. Each molecule has square-planar geometry for palladium with the aryl ring tilted by 76.2(4) and 67.1(3)° to the coordination plane, respectively. The crystal examined by X-ray diffraction exhibits significant substitutional disorder at one site: [PdX(C6H4(OCH2Ph)-4)(bpy)] (X ) Me (71%), Cl (29%)).
