Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 24 for “"transmetalation"”.
-
Pre-transmetalation intermediates in the Suzuki-Miyaura reaction revealed: the missing link
… able to detect and characterize the first pre-transmetalation intermediate “The Missing Link” in the Suzuki-Miyaura reaction. The ability to confirm the intermediacy of pre-transmetalation intermediates has provided the opportunity to clarify mechanistic aspects of the transfer of the organic …
-
Transmetalation from boronic esters to arylpalladium complexes without prior hydrolysis – mechanistic studies and preparative applications in the anhydrous, Suzuki-Miyaura cross-coupling reaction
… cross-coupling methods. For the first time, pre-transmetalation intermediates incorporating boronic esters have been characterized, proving the competency of boronic esters to undergo transmetalation without prior hydrolysis. Boronic ester structure was found to have a significant impact on both …
-
Palladium-Catalyzed Cross-Coupling Reactions of Organosilanols: I. New Methods That Employ Alkynylsilanols and Bissilyl Reagents. II. Mechanistic Analysis of the Cross-Coupling of Aryldimethylsilanolates
… of aryldimethylsilanolates demonstrated that transmetalation proceeds directly from an arylpalladium(II) silanolate intermediate without external activation. Arylpalladium(II) silanolate complexes bearing phosphine ligands were isolated and characterized. These complexes produce biaryl …
-
I. Mechanistic significance of the Si-O-Pd linkage in the cross-coupling of organosilanolates; II. Applications of the water-gas shift reaction in organic synthesis
… such intermediates, two mechanistically distinct transmetalation pathways have been demonstrated: (1) transmetalation via a neutral 8-Si-4 intermediate (thermal transmetalation); (2) transmetalation via an anionic 10-Si-5 intermediate (activated transmetalation). In general, potassium salts of …
-
Preparative and mechanistic aspects of palladium-catalyzed cross-coupling reactions of alkali-metal arylsilanolates
… has revealed a dual mechanistic pathway. The transmetalation can occur by a thermal process via an 8-Si-4 intermediate without the need for anionic activation. Additionally, arylsilanolates can serve as activators for transmetalation via a hypervalent 10-Si-5 siliconate intermediate. The …
-
Prediction of higher selectivity catalysts by a computer driven workflow and machine learning and computational investigation of boronate esters in the Suzuki-Miyaura cross coupling
… of boronic ester structure on the rate of transmetalation. Here we find that the activation barrier for transmetalation is dependent on the interplay between ground state destabilization of a Pd-O dative interaction and hyperconjugative activation of the Cipso-B σ bond.
-
Photoredox Generated Radicals In Csp2-Csp3 Bond Construction
… intermediates associated with a traditional transmetalation. To overcome this problem, we have pioneered an alternate, single-electron pathway involving 1) initial oxidation of an alkylmetallic reagent, 2) oxidative alkyl radical capture at a metal center, and 3) subsequent reduction of the …
-
Palladium-Catalyzed Alkenylsilanol Cross -Coupling Reactions: Method Development and Mechanistic Analysis
The transmetalation mechanism was examined through the natural abundance 13C NMR kinetic isotope effect (KIE) studies. This provided evidence for either palladium-olefin complexation or a Heck-type carbometalation as the turnover-limiting step for these cross-coupling reactions.
-
Studies on the Silanol-Based Cross-Coupling Reaction: (1) Development of Methods for the Synthesis of Aryl and Heteroaryldimethysilanols, (2) Expansion of the Substrate Scope of the Cross-Coupling Reaction and (3) Investigations on the Transmetalation of Organosilanols to Transition Metals
To further illuminate the mechanism of transmetalation of alkenyldimethylsilanols a number of molecular traps have been designed, synthesized and subjected to the cross-coupling reaction. A clear preference for formation of the cross-coupling products was observed in these investigations.
-
Ligand design principles for perfecting stereoretention in Suzuki-Miyaura cross-coupling of unactivated CSP3 boronic acids
… between stereoretentive and stereoinvertive transmetalation mechanisms. Achieving perfect transfer of stereochemistry from building blocks to products required that one of these transmetalation pathways be completely mitigated. By systematically studying the effect of the phosphine ligand on …
-
Investigation of aryldimethylsilanolates in palladium-catalyzed cross-coupling reactions and development of chiral bis-hydrazone ligands for asymmetric aryl-aryl couplings
… complexes enable kinetic studies of the transmetalation step in the proposed catalytic cycle under stoichiometric conditions. Hammett analysis reveals that electron-donating groups on the silicon nucleophile and electron-withdrawing groups on the aryl halide electrophile accelerate this …
-
Synthesis and Characterization of some Thallium Salt Complexes
… rhenium and manganese pyridazines through transmetalation of the thallium salts. The off-metal route of synthesis was followed as opposed to the previously reported on-metal route. Characterization was performed by 1H-NMR, 13CNMR, and IR.</p> <p>Additionally, research has begun on …
-
The development of palladium-catalyzed cross-coupling reactions of allylic silanolate salts with aromatic bromides
… mechanistic picture involving initial gamma-transmetalation followed by direct reductive elimination or sigma–pi isomerization can rationalize all of the observed trends. The stereochemical course of palladium-catalyzed cross-coupling reactions of an enantioenriched, alpha-substituted, …
-
Synthesis of Rhenium and Manganese Pyridazoal Complexes
… to Rhenium and Magnenese complexes through transmetalation. We have had success with the off-metal route at both higher yields and greater purity than the previous published on-metal route. These compounds have been fully characterized by <sup>1</sup>H NMR, <sup>13</sup>C NMR, IR, and …
-
Zirconocene-Mediated Carbonylative Coupling of Grignard Reagents and Cancer Prevention via Compounds that Modulate 15-PGDH
… access to acyl zirconium reagents through transmetalation of Grignard reagents with zirconocene dichloride under a CO atmosphere. This protocol generates acyl zirconium(IV) complexes that are inaccessible with the Schwartz reagent, including those derived from secondary and tertiary alkyl …
-
Preparation and reactions of some organic derivatives of manganese carbonyl compounds
… (I)). Orthomercurated aryl ketones obtained via transmetalation of orthomanganated ketones with mercuric chloride allowed a comparison of the product distribution for Pd(II)-promoted methyl acrylate coupling of an orthomercurated precursor 4-acetyl-2,5-dimethylthien-3-ylmercury(II) chloride (112) …
-
Synthesis, characterization, and catalytic reactivity of first-row transition metal CCC pincer complexes
… and nickel. An alternate metalation method, transmetalation from zirconium, into similar CCC pincer ligand frameworks has been previously established by the Hollis group. Utilizing a similar procedure zirconium complexes were synthesized and characterized (ArCCC)Zr(IV)X3 (Ar = Mes, DIPP). The …
-
Synthesis of Well-Defined N-Heterocyclic Carbene (NHC) Complexes of Late Transition Metals
… mono-NHC complexes appears easier specially by transmetalation starting from silver(I) NHC complexes. The reactivity of both metals NHC complexes is directly related to the strength of the metal-carbene bond. The gold(I) cation firmly bound to the carbene, undergoes oxidative addition with …
-
New Strategies for the Synthesis of Amines, Ethers and Small Strained Rings
… reagents. The first method involves the transmetalation of aryl Grignard, organolithium, or organozinc reagents to the corresponding organocopper species and subsequent reaction with a di-tert-butyl NH-oxaziridine. The use of less basic organocopper reagents expands the substrate scope to …
-
Palladium-catalyzed reactions of ammonia, carbon monoxide, and cyanide
… of 0.8-1 mol %. LiCl was shown to influence the transmetalation of arylpalladium chloride complexes with Zn(CN)2. In addition, the isolation and characterization of arylpalladium cyanide complexes that undergo reductive elimination to form arylnitriles have been demonstrated. The rates of …
Page 1 of 2