Onium compounds examples

Also the reaction of triphenylarsenic dihalides with acetonitrile leads to the onium compounds.243,244 An example... 

The copolymerization between trioxane and suitable comonomers (ethylene oxide, 1,3-dioxolane, diethylene glycol formal, 1,4-butane diol formal in amounts of 2-5% by weight) is performed using cationic initiators. The cationic initiators could be Lewis acids, such as BF3 or its etherate BF3Bu20 which was used, for example by Celanese (the mechanism of this reaction was studied in detail [163,164]) or protic acids such as perchloric acid, perfluoroalkane sulfonic acids and their esters and anhydrides. Heteropoly acids were used and also a series of carbenium, oxocarbenium salts, onium compounds, and metal chelates. To regulate the molecular weight chain-transfer agents, such as methylal and butylal, are added. 

Coinitiators according to route A are electron-deficient materials. Representative examples are onium compounds and triazines [269, 563], The free energy of photoinduced electron transfer (AGei) between a photosensitizer and a coinitiator is described by Eq. (64), in which /i, /2 is the half-wave oxidation potential (route A e J2 is representative for the sensitizer route B Fox" stands for the coinitiator), is the half-wave reduction potential (route A red is representative for the coinitiator route B stands for the sensitizer), and oo is the... 

The stability of these bismuthonium salts (82) - (85) depends on the nature of the anionic counterpart and of the fourth ligand. The allyl derivatives (84) are too unstable to be isolated. On the other hand, the tetrafluoroborate salts of the derivatives of the three other types of onium compounds are thermally stable. Ligand coupling- type products are formed with more nucleophilic anions, for example during the attempted exchange of anion with bromide or iodide, or during the slow decomposition of a solution of bismuthonium tosylates in chloroform. ... 

Both the trans- and cis- biosynthetic systems can be regulated. The carotenoid pattern observed is determined essentially by the nature of onium compounds employed. For example, 2-diethylamino-ethyl-4-methylphenylether caused a large accumulation of all trans-lycopene (ip, ip-carotene), whereas... 

Early work focused on compounds with open-chain carbenes generally synthesized in the coordination sphere of the gold atom, for example, by addition of amines or alcohols to isocyanide ligands in the corresponding gold complexes. Subsequent synthetic approaches have relied on the in situ deprotonation of onium salt precursors by a... 

These reactions are covered in other chapters of Volume 11 (Chapters 11.06 and 11.07). This part deals only with examples which are in connection with other sections of this chapter. Additions of metallocarbenoids to unsaturated partners have been extensively studied. Most of the initial studies have involved the transition metal-catalyzed decomposition of cr-carbonyl diazo compounds.163,164 Three main reaction modes of metallocarbenoids derived from a-carbonyl diazo precursor are (i) addition to an unsaturated C-C bond (olefin or alkyne), (ii) C-H insertion, and (iii) formation of an ylid (carbonyl or onium).1 5 These reactions have been applied to the total synthesis of natural... 

Radicals are generated at the anode by oxidation of carbanions (Scheme lb), for example, alkoxides and carboxylates (see Chapter 5, 6), and at the cathode by reduction of protonated carbonyl compounds or onium salts (Scheme Ic) (see Chapter 7). Thereby, a wide choice of different radical structures can be mildly and simply... 

Recently, many similar systems have been reported in the literature. Examples include acid-photogenerating compounds in combination with t-BOC-protected maleimide or hydroxyphenyl maleimide copolymers (69, 70), tert-butyl ethers of phenolic resins (71), silylated phenolic resins (72, 73), and polycarbonates that contain acid-labile linkages in their backbone (74, 75). Onium-salt-photogenerated acid has also been used in another two-component system to catalytically depolymerize polyphthalaldehyde (76). 

An interesting example of oxygen activation by onium salts of nontransition elements has been claimed. Sulfonium salts were found to be especially effective,211 and it was proposed212-214b that dioxygen complexes of sulfonium compounds can initiate autoxidations via hydrogen transfer with hydrocarbons, e.g.,... 

All attempts to prepare a spirocyclic hexacoordinate antimonate complex 168 and a tetracoordinate spirostibonium ion 167 or onium-ate combinations of these, according to structural and synthetic principles elaborated with corresponding phosphorus and arsenic compounds, met with failure138). When, for example,-... 

Ternary iodo compounds are formed only with large cations the onium salts appear to be invariably examples of [Mnl4]2- tetrahedra, although both CsMnI3 and TlMnI3 give examples of [Mnlfi] polymers (Table 34). 

Onium salts can also be used to support reagents that would transform a substrate. After reaction the IL phase can be recovered and the reagent regenerated for being reused in another cycle. For example, carboxylic acids have been supported on onium halides. Simply synthesized by quatemarisation of methylimidazole followed by acid hydrolysis, this compound can react with epoxides to afford halo-hydrines in 76-95% yields [58], Additionally, an OS supported version of TEMPO has been used in oxidation of alcohol into ketone [59] (Fig. 21). 

Thus, sulfurane species [10-S-4(C4)] have been considered to be intermediates or transition states in the reactions of the corresponding onium salts or oxides with various organometallic reagents. Especially in the case of sulfurane species [ 10—S—4(C4)], no one has succeeded in direct detection except for one example. Therefore, little remains known about the properties of these compounds. 

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