Unsaturated substrates styrene

Oxidative addition of the silyl species to nickel is followed by insertion of unsaturated substrates. Zero-valent nickel complexes, and complexes prepared by reducing nickel acetylacetonate with aluminum trialkyls or ethoxydialkyls, and in general Ziegler-Natta-type systems, are effective as catalysts (244, 260-262). Ni(CO)4 is specific for terminal attack of SiHCl3 on styrene (261). 

One of the most useful classes of metal and phase transfer catalyzed reactions are carbonylation reactions. Cobalt carbonyl is a valuable catalyst for such processes(1 ). When used in conjunction with methyl iodide, acetylcobalt carbonyl [CH3C0Co(C0) ] is generated and can undergo addition to various unsaturated substrates including alkynes and Schiff bases. In addition, one can add this species to styrene oxides to give the enol... 

Conjugated dienes, styrenes and electron-rich alkenes are cyclopropanated with ethyl diazoacetate using a triarylamminium salt of appropriate oxidation potential as a cata-lyst/initiator (equation 96)185. These reactions are initiated by electron transfer from the unsaturated substrate to the amminium ion and the double additions of the diazo esters to the conjugated dienes are effectively suppressed. Cyclopropanes geminally bearing two... 

One of the earliest examples of the synthetic promise of radical reactions for preparing polycyclic products was provided by Corey s y-lactone synthesis. This approach was actually based on a well-known reaction of a-carbonyl radicals, generated by manganese(iii) oxidation of carboxylic acids, with unsaturated substrates. The mechanism of the basic steps shown for the preparation of lactone 418 (Scheme 2.140) involves initial addition of the a-carbonyl radical 419 to the double bond of styrene, followed by oxidation of the radical intermediate 419a to carbocation 419b, and subsequent intramolecular reaction with the carboxyl nucleophile to yield the lactone product. 

In addition to the work described here, experiments with styrenes and a,)8-unsaturated acids, esters and ketones, as well as related halides (24), suggest certain generalizations concerning the effect of structure on organocobalt complex stability and catalysis. Table IX lists several organocobalt complexes, whose preparations, either by reaction of the halide with pentacyanocobaltate(II) or by addition of hydrido complex to the corresponding unsaturated substrate, have been attempted. In many cases, both methods were used. 

The asymmetric synthesis of aziridines can be achieved by a number of methods. The best alkene substrates are typically a,3-unsaturated esters, styrenes or chromenes, with aziridination by PhI=NTs and a metal-chiral ligand complex. For example, aziridination of tert-butyl cinnamate 73 occurs highly enantioselec-tively with copper(I) triflate and a bisoxazoline ligand (5.77). 

The coupling reaction of polybromo ketones and unsaturated substrates provides a new method for the construction of various cyclic organic structures. The oxyallyliron(Il) species can be trapped efficiently by aromatic olefins to give 3-arylcyclopentanones (Noyori et al., 1973d). )3-cw-Deuterio-styrene, as olefinic substrate, undergoes stereospecific cycloaddition, though... 

Note that based on earlier experimental studies from Sharpless group, it was concluded that some n-n stacking may bring important consequences for tile reaction enantioselectivity when unsaturated substrates are used. For example, whereas dihydroxylation of styrene afforded the product witii 97% ee and vinylcyclohexane afforded the product with 84% ee. The value 84% for nonsaturated substrate can be explained in terms of weak C(sp )-H... ji hydrogen-bonding interactions between a substrate and a catalyst. Similar C(sp )-H...n hydrogen-bonding interactions between the... 

The catalytic properties of the sulfonated diphosphine-stabilized RuNPs and sulfonated diphosphine/cyclodextrin-stabilized RuNPs were compared in the hydrogenation of unsaturated model substrates (styrene, acetophenone, and w-methylanisole) in biphasic liquid-hquid conditions (i.e., ruthenium aqueous colloidal solution and organic substrate no added solvent). Whilst all of these RuNPs displayed suitable performances in catalysis, different activities and selec-tivities were observed. This highhghted that supramolecular interactions on the metallic surface in the presence of a cyclodextrin control the catalytic reactivity of the nanocatalysts. Interestingly the CD acts as a phase-transfer promotor, which... 

Norton has thoroughly investigated half-sandwich chromium carbonyl derivatives, inspired by literature reports of a radical pathway for the hydrogenation of certain unsaturated substrates by low-valent hydride complexes (Figure 28), that is, anthracene/HCo (CO)4, a-methylstyrene/HMt L (Mf L = Mn (CO)s, or CpM (CO)3 with M = Mo or W ), and styrene/HCo (CO)4. Note that the initial equilibrium corresponds to the p-H atom transfer process in CCT and that all above-mentioned substrates lead to highly stabilized radicals. 

The catalytic properties of the sulfonated diphosphine-stabilized Ru NPs and sulfonated diphosphine/CD-stabilized Ru NPs were compared in the hydrogenation of unsaturated model substrates (styrene, acetophenone, and m-methylanisole) in biphasic liquid-liquid conditions (i.e., ruthenium aqueous colloidal solution and organic substrate no added solvent). 

A modified latex composition contains a phosphorus surface group. Such a latex is formed by emulsion polymerization of unsaturated synthetic monomers in the presence of a phosponate or a phosphate which is intimately bound to the surface of the latex. Thus, a modified latex containing 46% solids was prepared by emulsion polymerization of butadiene, styrene, acrylic acid-styrene seed latex, and a phosphonate comonomer in H20 in the presence of phosphated alkylphenol ethoxylate at 90°C. The modified latex is useful as a coating for substrates and as a binder in aqueous systems containing inorganic fillers employed in paper coatings, carpet backings, and wallboards [119]. 

Hydroaminomethylahon of alkenes [path (c)j wiU not be considered [12]. This review deals exclusively with the hydroaminahon reaction [path (d)], i.e. the direct addition of the N-H bond of NH3 or amines across unsaturated carbon-carbon bonds. It is devoted to the state of the art for the catalytic hydroamination of alkenes and styrenes but also of alkynes, 1,3-dienes and allenes, with no mention of activated substrates (such as Michael acceptors) for which the hydroamination occurs without catalysts. Similarly, the reachon of the N-H bond of amine derivatives such as carboxamides, tosylamides, ureas, etc. will not be considered. 

The success of the cross-metathesis reactions involving styrene and acrylonitrile led to an investigation into the reactivity of other Ji-substituted terminal alkenes [27]. Vinylboranes, enones, dienes, enynes and a,p-unsaturated esters were tested, but all of these substrates failed to undergo the desired cross-metathesis reaction using the molybdenum catalyst. 

Under optimized conditions regarding the choice of Br0nsted acid (mandelic acid 20), stoichiometry (1 1 ratio 9 and mandelic acid 20), solvent (the respective alcohol neat conditions), temperature (rt or 50°C), and catalyst loading (lmol% 9 and lmol% mandelic acid 20) electron-rich and electron-deficient styrene oxides underwent alcoholysis with simple aliphatic, stericaUy demanding as well as unsaturated and acid-labile alcohols. The completely regioselective (>99%) alcoholysis was reported to produce the corresponding P-aUcoxy alcohols 1-10 in moderate (41%) to good (89%) yields without noticeable decomposition or polymerization reactions of acid-labile substrates (Scheme 6.27). Notably, aU uncatalyzed reference experiments showed no conversion even after two weeks under otherwise identical conditions. 

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