Olefins phase-transfer catalysis

In dihalocarbene generation by phase-transfer catalysis the following steps seem to be involved (15) formation of CX anions dynamically anchored at the boundary reversible detachment with the help of the catalyst reversible carbene formation [Q+ CX3 ] [Q + X ] + CX2 addition to olefin. 

Contents Introduction and Principles. - The Reaction of Dichlorocarbene With Olefins. - Reactions of Dichlorocarbene With Non-Olefinic Substrates. -Dibromocarbene and Other Carbenes. - Synthesis of Ethers. - Synthesis of Esters. - Reactions of Cyanide Ion. - Reactions of Superoxide Ions. - Reactions of Other Nucleophiles. - Alkylation Reactions. - Oxidation Reactions. - Reduction Techniques. - Preparation and Reactions of Sulfur Containing Substrates. -Ylids. - Altered Reactivity. - Addendum Recent Developments in Phase Transfer Catalysis. 

The phase-transfer catalysis method has also been utilized effectively for addition of dichlorocarbene to olefins,4 as well as for substitution and elimination reactions, oxidations, and reductions.18 The preceding procedure in this volume is another example.13... 

Monflier and co-workers recently described a new approach based on the use of chemically modified /3-cyclodextrins to peform efficiently the functionalization of water-insoluble olefins in a two-phase system. These compounds behave as inverse phase transfer catalysis, i.e., they transfer olefins into the aqueous phase via the formation of inclusion complexes.322... 

Thermoregulated Phase Transfer Catalysis - A conceptual advance in the field of biphasic hydroformylation of higher olefins is the use of rhodium catalysts generated from nonionic tenside phosphines, such as ethoxylated tris(4-... 

The reaction of an a-halo sulfone with a base to give an olefin is called the Ramberg-Backlund reaction.309 The reaction is quite general for a-halo sulfones with an a hydrogen, despite the unreactivity of a-halo sulfones in normal Sn2 reactions (p. 344). Halogen reactivity is in the order I > Br > Cl. Phase transfer catalysis has been used.310 In general, mixtures of cis and trans isomers are obtained, but usually the less stable cis isomer predominates. The mechanism involves formation of an episulfone and then elimination of... 

Systematic studies of the dicyclopropanation of olefinic sugars have been published [194], Dichlorocarbene, generated under phase-transfer catalysis reacts with 2,3-unsaturated pyranosides, such as 161 to yield a single isomer of the expected cyclopropane 162 (Scheme 55). A typical procedure is given in Section IE. The reaction is also possible with an enol... 

Phase-transfer catalysis has been developed by the combination of Keggin-type heteropolyanions and quaternary countercations such as tetrahexyl-ammonium or cetylpyridinium ion. The oxidations of alcohols (306), allyl alcohols (307), olefins (308), alkynes (309), /J-unsaturated acids (310), v/ c-diols (311), phenol (312), and amines (313) are the examples. 

In particular, it is not only the cinchona alkaloids that are suitable chiral sources for asymmetric organocatalysis [6], but also the corresponding ammonium salts. Indeed, the latter are particularly useful for chiral PTCs because (1) both pseudo enantiomers of the starting amines are inexpensive and available commercially (2) various quaternary ammonium salts can be easily prepared by the use of alkyl halides in a single step and (3) the olefin and hydroxyl functions are beneficial for further modification of the catalyst. In this chapter, the details of recent progress on asymmetric phase-transfer catalysis are described, with special focus on cinchona-derived ammonium salts, except for asymmetric alkylation in a-amino acid synthesis. 

The catalytic asymmetric epoxidation of electron-deficient olefins, particularly a,P-unsaturated ketones, has been the subject of numerous investigations, and as a result a number of useful methodologies have been elaborated [44], Among these, the method utilizing chiral phase-transfer catalysis occupies a unique position in terms of its practical advantages. Moreover, it also allows the highly enantioselective epoxidation of trans-a,P-unsaturated ketones, particularly chalcone. 

A similar procedure can be applied to the synthesis of a series of 5-nitroimidazoles83 with antibacterial properties.The S l reaction of various l-alkyl-2-chloromethyl-5-nitroimidazoles (23) with heterocyclic nitronate anions prepared from 3-nitrolactams, under phase transfer catalysis, afforded trisubstituted olefins (equation 33). 

Y. Mahha, L. Salles, J.-Y. Piquemal, E. Briot, A. Atlamsani, J.-M. Bregeault, Environmentally friendly epoxidation of olefins under phase-transfer catalysis conditions with hydrogen peroxide, J. Catal. 249 (2007) 338. 

Reaction-Controlled Phase-Transfer Catalysis for Epoxidation of Olefins... 

This chapter will present recent progress made in reaction-controlled phase-transfer catalysis for the epoxidation of olefins, focusing on work with hetero-pol)q5hosphotungstates and quaternary ammonium ions from our group. We have systemically investigated the influence of composition of the heteropoly anion and various quaternary ammonium ions on the catalyst activity. The epoxidation of propylene, allyl chloride, and others olefins and the stability of the catalyst in recycle will be summarized and discussed in detail. 

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