Other affiliations: Ben-Gurion University of the Negev
Bio: Yoel Sasson is an academic researcher from Hebrew University of Jerusalem. The author has contributed to research in topics: Catalysis & Aqueous solution. The author has an hindex of 45, co-authored 349 publications receiving 7097 citations. Previous affiliations of Yoel Sasson include Ben-Gurion University of the Negev.
Papers published on a yearly basis
01 Jan 1997
TL;DR: Nucleophilic aliphatic and aromatic substitutions in phase transfer catalysis mechanism and synthetic applications kinetics and mechanism in phase-transfer catalysis synthesis and properties as mentioned in this paper.
Abstract: Nucleophilic aliphatic and aromatic substitutions in phase transfer catalysis mechanism and synthetic applications kinetics and mechanism in phase transfer catalysis synthesis and properties of quaternary ammonium phase transfer catalysts phase transfer reactions under basic conditions applications of phase transfer catalysis in industrial organic chemistry PTC in polymer chemistry PTC in carbohydrate chemistry PTC in heterocyclic chemistry phase transfer catalysis in oxidation processes organometallic reactions under phase-transfer conditions sonochemical and microwave activation in phase transfer catalysis analytical applications of phase transfer catalysis triphase catalysis chiral phase transfer chemical modification of polymers via phase transfer catalysis phase transfer catalysis of uncharged species.
TL;DR: In this article, a visible-light-driven photocatalyst with excellent catalytic activity was fabricated, via a very simple procedure and at room temperature, a unique visible light-driven catalytic material with excellent activity.
Abstract: With careful rational optimization and substantial simplification of the syntheses of the recently reported alloys BiO(ClxBr1–x), we fabricated, via a very simple procedure and at room temperature, a unique visible-light-driven photocatalyst with excellent activity. The alloy BiOCl0.875Br0.125 totally decomposed 15 mg/L aqueous Rhodamine B solution within 120 s upon irradiation with visible light (λ > 422 nm). The transparent substrate acetophenone was also swiftly destroyed under the above conditions. The catalyst maintained partial activity even after switching off the light source. Initial mechanistic studies clearly suggest that the mode of action of these materials is fundamentally different from previously reported photocatalytic mechanisms. Evidently, the putative molecular mechanism does not engage dye photosensitization or oxygen radicals.
TL;DR: In this article, a facile and effective method to modify the photocatalytic performance of a bismuth oxybromide (BiOBr) semiconductor through the fabrication of a heterojunction with a hydrated Bismuth oxide (BHO) is reported.
Abstract: In this study, a facile and effective method to modify the photocatalytic performance of a bismuth oxybromide (BiOBr) semiconductor through the fabrication of a heterojunction with a hydrated bismuth oxide (BHO) is reported. The new yBiOBr-(1 – y)BHO heterojunction, synthesized by a simple hydrothermal method, exhibits a high photocatalytic activity under visible light irradiation for the photodegradation of typical organic pollutants in water, such as Rhodamine B (RhB) and acetophenone (AP). Both the individual BiOBr and BHO components show very low photocatalytic efficiency. Furthermore, the unique photocatalytic performance of the new hybrid material was demonstrated through the uphill photocatalytic reaction that involves the oxidation of potassium iodide (KI) to triiodide. The remarkable photocatalytic activity of the coupled system is directly related to the effectual charge carrier separation due to the formation of the heterostructure. 0.9BiOBr-0.1BHO shows a higher photocatalytic activity as comp...
TL;DR: In this paper, a complete reaction mechanism is proposed, wherein the free-radical oxidation obeys Kochi's mechanism, and the heterolytic dehydrogenation is based on either a high-valent CuIVO species or a [Cu(OH)Cl]2 species.
Abstract: Allylic and benzylic alcohols were oxidized in good yields to the respective ketones by tert-butyl hydroperoxide (TBHP) in the presence of copper salts under phase-transfer catalysis conditions. This dehydrogenation was found to proceed via a heterolytic mechanism. CuCl2, CuCl, and even copper powder were equally facile as catalysts, as they were all transformed in situ to Cu(OH)Cl which was extracted into the organic phase by the phase-transfer catalyst (PTC). Deuterium labeling experiments evidenced the scission of the benzylic C–H bond in the rate-determining step. Nonproductive TBHP decomposition was not observed in the presence of the alcohol substrates. Conversely, the oxygenation of π-activated methylene groups in the same medium was found to be a free radical process, and the major products were the appropriate tert-butyl peroxides. Catalyst deactivation, solvent effects, and extraction effects are discussed. By applying Minisci’s postulations concerning the relative reactivity of TBHP molecules towards tert-butoxyl radicals in protic and nonprotic environments, the coexistence of the homolytic and the heterolytic pathways can be explained. A complete reaction mechanism is proposed, wherein the free-radical oxidation obeys Kochi’s mechanism, and the heterolytic dehydrogenation is based on either a high-valent CuIVO species or a [Cu(OH)Cl]2 species.
TL;DR: A number of improvements have developed the former process into an industrially very useful and attractive method for the construction of aryl -aryl bonds, but the need still exists for more efficient routes whereby the same outcome is accomplished, but with reduced waste and in fewer steps.
Abstract: The biaryl structural motif is a predominant feature in many pharmaceutically relevant and biologically active compounds. As a result, for over a century 1 organic chemists have sought to develop new and more efficient aryl -aryl bond-forming methods. Although there exist a variety of routes for the construction of aryl -aryl bonds, arguably the most common method is through the use of transition-metalmediated reactions. 2-4 While earlier reports focused on the use of stoichiometric quantities of a transition metal to carry out the desired transformation, modern methods of transitionmetal-catalyzed aryl -aryl coupling have focused on the development of high-yielding reactions achieved with excellent selectivity and high functional group tolerance under mild reaction conditions. Typically, these reactions involve either the coupling of an aryl halide or pseudohalide with an organometallic reagent (Scheme 1), or the homocoupling of two aryl halides or two organometallic reagents. Although a number of improvements have developed the former process into an industrially very useful and attractive method for the construction of aryl -aryl bonds, the need still exists for more efficient routes whereby the same outcome is accomplished, but with reduced waste and in fewer steps. In particular, the obligation to use coupling partners that are both activated is wasteful since it necessitates the installation and then subsequent disposal of stoichiometric activating agents. Furthermore, preparation of preactivated aryl substrates often requires several steps, which in itself can be a time-consuming and economically inefficient process.
TL;DR: The Review presents the recent developments and the use of NP catalysis in organic synthesis, for example, in hydrogenation and C--C coupling reactions, and the heterogeneous oxidation of CO on gold NPs.
Abstract: Interest in catalysis by metal nanoparticles (NPs) is increasing dramatically, as reflected by the large number of publications in the last five years. This field, "semi-heterogeneous catalysis", is at the frontier between homogeneous and heterogeneous catalysis, and progress has been made in the efficiency and selectivity of reactions and recovery and recyclability of the catalytic materials. Usually NP catalysts are prepared from a metal salt, a reducing agent, and a stabilizer and are supported on an oxide, charcoal, or a zeolite. Besides the polymers and oxides that used to be employed as standard, innovative stabilizers, media, and supports have appeared, such as dendrimers, specific ligands, ionic liquids, surfactants, membranes, carbon nanotubes, and a variety of oxides. Ligand-free procedures have provided remarkable results with extremely low metal loading. The Review presents the recent developments and the use of NP catalysis in organic synthesis, for example, in hydrogenation and C--C coupling reactions, and the heterogeneous oxidation of CO on gold NPs.
TL;DR: In this article, it was shown that the same alkylhydridoplatinum(IV) complex is the intermediate in the reaction of ethane with platinum(II) σ-complexes.
Abstract: ion. The oxidative addition mechanism was originally proposed22i because of the lack of a strong rate dependence on polar factors and on the acidity of the medium. Later, however, the electrophilic substitution mechanism also was proposed. Recently, the oxidative addition mechanism was confirmed by investigations into the decomposition and protonolysis of alkylplatinum complexes, which are the reverse of alkane activation. There are two routes which operate in the decomposition of the dimethylplatinum(IV) complex Cs2Pt(CH3)2Cl4. The first route leads to chloride-induced reductive elimination and produces methyl chloride and methane. The second route leads to the formation of ethane. There is strong kinetic evidence that the ethane is produced by the decomposition of an ethylhydridoplatinum(IV) complex formed from the initial dimethylplatinum(IV) complex. In D2O-DCl, the ethane which is formed contains several D atoms and has practically the same multiple exchange parameter and distribution as does an ethane which has undergone platinum(II)-catalyzed H-D exchange with D2O. Moreover, ethyl chloride is formed competitively with H-D exchange in the presence of platinum(IV). From the principle of microscopic reversibility it follows that the same ethylhydridoplatinum(IV) complex is the intermediate in the reaction of ethane with platinum(II). Important results were obtained by Labinger and Bercaw62c in the investigation of the protonolysis mechanism of several alkylplatinum(II) complexes at low temperatures. These reactions are important because they could model the microscopic reverse of C-H activation by platinum(II) complexes. Alkylhydridoplatinum(IV) complexes were observed as intermediates in certain cases, such as when the complex (tmeda)Pt(CH2Ph)Cl or (tmeda)PtMe2 (tmeda ) N,N,N′,N′-tetramethylenediamine) was treated with HCl in CD2Cl2 or CD3OD, respectively. In some cases H-D exchange took place between the methyl groups on platinum and the, CD3OD prior to methane loss. On the basis of the kinetic results, a common mechanism was proposed to operate in all the reactions: (1) protonation of Pt(II) to generate an alkylhydridoplatinum(IV) intermediate, (2) dissociation of solvent or chloride to generate a cationic, fivecoordinate platinum(IV) species, (3) reductive C-H bond formation, producing a platinum(II) alkane σ-complex, and (4) loss of the alkane either through an associative or dissociative substitution pathway. These results implicate the presence of both alkane σ-complexes and alkylhydridoplatinum(IV) complexes as intermediates in the Pt(II)-induced C-H activation reactions. Thus, the first step in the alkane activation reaction is formation of a σ-complex with the alkane, which then undergoes oxidative addition to produce an alkylhydrido complex. Reversible interconversion of these intermediates, together with reversible deprotonation of the alkylhydridoplatinum(IV) complexes, leads to multiple H-D exchange
TL;DR: Reaction of R,â-Unsaturated Carbonyl Compounds 3127: Reaction of R-UnSaturated Carbonies 3127 7.1.6.
Abstract: 4.2.8. Reductive Coupling 3109 5. Reaction of Aromatic Compounds 3110 5.1. Electrophilic Substitutions 3110 5.2. Radical Substitution 3111 5.3. Oxidative Coupling 3111 5.4. Photochemical Reactions 3111 6. Reaction of Carbonyl Compounds 3111 6.1. Nucleophilic Additions 3111 6.1.1. Allylation 3111 6.1.2. Propargylation 3120 6.1.3. Benzylation 3121 6.1.4. Arylation/Vinylation 3121 6.1.5. Alkynylation 3121 6.1.6. Alkylation 3121 6.1.7. Reformatsky-Type Reaction 3122 6.1.8. Direct Aldol Reaction 3122 6.1.9. Mukaiyama Aldol Reaction 3124 6.1.10. Hydrogen Cyanide Addition 3125 6.2. Pinacol Coupling 3126 6.3. Wittig Reactions 3126 7. Reaction of R,â-Unsaturated Carbonyl Compounds 3127