And phase transfer catalysts

In this case, yields >95% of the tertiary phosphine are obtained. Tributylphosphine is readily converted to tetraalkylphophonium salts by reaction with an alkyl haUde. These compounds are used commercially as biocides and phase-transfer catalysts. 

Based on this hypothesis we reversed the order in which the reactants are brought into contact. Consequently, we added an aqueous solution of BPA, sodium hydroxide, and phase transfer catalyst into a well-stirred solution of cyanogen bromide in carbon tetrachloride. Under these conditions poly(iminocarbonates) of high molecular weight were readily obtained (Fig. 8.)... 

With few exceptions, by far most applications of tetrazolium salts (e.g., analytical, photographic, and biochemical) utilize their reducibility to the corresponding formazan dyes. Tetrazolium salts, due to their resistance to acid and oxidation and the presence of a positive charge, find use in other applications such as antistatic agents and phase transfer catalysts. Over the past two decades, there have been thousands of citations regarding the applications of tetrazolium salts. Most of these citations are patents with similar or overlapping and even identical claims. Any attempt at completeness would be futile. The applications are sorted where discernible, and the earliest or the broadest claims are cited. 

In general, if condensation polymers are prepared with methylated aryl repeat units, free radical halogenatlon can be used to introduce halomethyl active sites and the limitations of electrophilic aromatic substitution can be avoided. The halogenatlon technique recently described by Ford11, involving the use of a mixture of hypohalite and phase transfer catalyst to chlorinate poly(vinyl toluene) can be applied to suitably substituted condensation polymers. 

Another palladium-catalyzed coupling reaction that has been successfully performed on soluble polymers is the Sonogashira coupling. Xia and Wang have presented an approach in which the PEG 4000 utilized simultaneously serves as polymeric support, solvent, and phase-transfer catalyst (PTC) in both the coupling and... 

Tab. 5.8 Reaction of catechol with /J-methallyl chloride (8 mmol) in the presence of base (2 mmol) and phase-transfer catalyst (0.2 mmol) under microwave irradiation.

The term phase transfer catalysis is also spelled as phase-transfer catalysis. In this review, we will adopt the former without hyphen. PTC means both phase transfer catalysis and phase transfer catalyst To avoid the confusion, full spellings will be adopted. 

The consecutive reaction of vinyl halides and alkenes with activated methylene systems [42] in the presence of a palladium catalyst and phase-transfer catalyst results from the addition of the methylene carbanion with the initially formed Heck product (Scheme 6.31) an intramolecular version of the reaction leads to the formation of bicycloalk-l-enes (Scheme 6.31) [42], The analogous combined coupling reaction of iodoarenes and activated methylene compounds with non-conjugated dienes under similar conditions forms the monoalkene (Scheme 6.31) [43]. 

If, however, PEG-400 is employed as the solvent and phase transfer catalyst, under a nitrogen atmosphere, then the monoacid is obtained in good yield. Since vinylic dibromides are easily synthesized from carbonyl compounds, this constitutes a valuable method for oxidative homologation(19). 

V-Alkylation of 3-hydroxypyridine results from direct treatment with an alkyl halide or dimethyl sulfate and alkali (59JA5140,57RTC58). Regioselectivity depends, however, on other substituents present as well as conditions. For example, 3-hydroxy-2-nitropyridine is exclusively O-alkylated with dimethyl sulfate and potassium carbonate (81MI20600) and 2-amino-3-hydroxypyridines are exclusively O-benzylated with benzyl chloride and alkali in a two phase system and phase transfer catalyst (Scheme 96) (81S971). 

The above synthetic methods for oxetane all involve formation of a new C—O bond. Cyclization by formation of a new C—C bond has been applied with compounds having benzylic or alkylic CH groups. Recent examples of this type of ring closure are the rearrangement of trans- 2,3-epoxycyclohexyl allyl ether by means of s-butyllithium and the dehydrochlorination of a-cyanobenzyl 2-chloroethyl ether with aqueous base and phase transfer catalyst (equation 86). Both reactions probably involve carbanion intermediates (76TL2115, 75MIP51300). 

Functionalized polymers are of interest in a variety of applications including but not limited to fire retardants, selective sorption resins, chromatography media, controlled release devices and phase transfer catalysts. This research has been conducted in an effort to functionalize a polymer with a variety of different reactive sites for use in membrane applications. These membranes are to be used for the specific separation and removal of metal ions of interest. A porous support was used to obtain membranes of a specified thickness with the desired mechanical stability. The monomer employed in this study was vinylbenzyl chloride, and it was lightly crosslinked with divinylbenzene in a photopolymerization. Specific ligands incorporated into the membrane film include dimethyl phosphonate esters, isopropyl phosphonate esters, phosphonic acid, and triethyl ammonium chloride groups. Most of the functionalization reactions were conducted with the solid membrane and liquid reactants, however, the vinylbenzyl chloride monomer was transformed to vinylbenzyl triethyl ammonium chloride prior to polymerization in some cases. The reaction conditions and analysis tools for uniformly derivatizing the crosslinked vinylbenzyl chloride / divinyl benzene films are presented in detail. 

Poly(vinylbenzyl chloride) (VBC) is an ideal starting material onto which a variety of functional groups can be attached through relatively simple reactions and mild reaction conditions. Functionalized polymers are of interest in a variety of applications including but not limited to fire retardants, selective sorption resins, chromatography media, controlled release devices and phase transfer catalysts. An example of the wide applicability of functionalized polymers is provided by trimethyl ammonium functionalized poly(VBC). 

Sauvagnat, B., Lamaty F., Lazaro, R. and Martinez, J., Polyethylene glycol (PEG) as polymeric support and phase-transfer catalyst in the soluble polymer liquid phase synthesis of ct-amino esters, Tetrahedron Lett., 1998, 39,821. 

An important group of surface-active nonionic synthetic polymers (nonionic emulsifiers) are ethylene oxide (block) (co)polymers. They have been widely researched and some interesting results on their behavior in water have been obtained [33]. Amphiphilic PEO copolymers are currently of interest in such applications as polymer emulsifiers, rheology modifiers, drug carriers, polymer blend compatibilizers, and phase transfer catalysts. Examples are block copolymers of EO and styrene, graft or block copolymers with PEO branches anchored to a hydrophilic backbone, and star-shaped macromolecules with PEO arms attached to a hydrophobic core. One of the most interesting findings is that some block micelle systems in fact exists in two populations, i.e., a bimodal size distribution. 

As discussed in Section 10.1, asymmetric epoxidation of C=C double bonds usually requires electrophilic oxygen donors such as dioxiranes or oxaziridinium ions. The oxidants typically used for enone epoxidation are, on the other hand, nucleophilic in nature. A prominent example is the well-known Weitz-Scheffer epoxidation using alkaline hydrogen peroxide or hydroperoxides in the presence of base. Asymmetric epoxidation of enones and enoates has been achieved both with metal-containing catalysts and with metal-free systems [52-55]. In the (metal-based) approaches of Enders [56, 57], Jackson [58, 59], and Shibasaki [60, 61] enantiomeric excesses > 90% have been achieved for a variety of substrate classes. In this field, however, the same is also true for metal-free catalysts. Chiral dioxiranes will be discussed in Section 10.2.1, peptide catalysts in Section 10.2.2, and phase-transfer catalysts in Section 10.2.3. 

The polycarbonate oligomers were prepared by solution or interfacial techniques (10,17,18). Methylene chloride and tetraethyl ammonium chloride served as the solvent and phase transfer catalyst, respectively. The block copolymerizations were performed essentially under interfacial reaction conditions. In the case of copolymerizations using the Bis-S polysulfone oligomers, it was necessary to use tetrachloroethane as the organic solvent. 

Tropones 2,4.6-Trimethylphenol (l)reacts withdichloro-ordibromocarbcne(halo-genoform and phase-transfer catalyst) to provide the dienones 2 and 3, which on reaction with Bu,SnH are both converted into 2,4,7-trimethyltropone (4). 

Oxidation of aikenes. KMn04 can be solubilized in CH2CI2 by an equimolar amount of benzyltriethylammonium chloride. This solution can be used for homogeneous oxidation of aikenes to intermediates that can be decomposed either to dialdehydes or to s-l,2-diols. In two-phase oxidations with KMnOa and phase-transfer catalysts, diols or carboxylic acids are obtained. ... 

A three-necked, round-bottomed flask equipped with a thermometer, reflux conductor, N, inlet and an overhead mechanical stirrer was charged sequentially with H O (5 mL), 50% NaOH (2 mL. 39 mmol), and adenine (2 g, 15 mmol). After the adenine had dissolved, a solution of benzylating reagent (16 mmol) and phase-transfer catalyst (5 mol%) in organic solvent (30-40 mL) was added. The system was stirred under reflux and then cooled to rt. The precipitated solids were filtered, washed with lIjO (2x10 mL), and dried in vacuo to give the crude bcnzylated adenine mixtures. For separation see ref 82. 

Zenkoh, T, Tanaka, H, Setoi, H, Takahashi, T, Solid-phase synthesis of aryl O-glycoside using aqueous base and phase transfer catalyst, Synlett, 867-870, 2002. 

Under the name Oxone an oxidation agent has been introduced, consisting of KHSO4-K2SO4-2KHSO5. Solid Oxone converts methylenic functions under anhydrous, biphasic conditions to carbonyl compounds under the catalytic influence of ligand-modified Mn porphyrins and phase-transfer catalysts (e. g., acetophenone is obtained from ethylbenzene). In the case of cyelohexane, e-caprolactone results as well as cyclohexanol and -one ([219 b, 241] cf. also Baeyer-Villiger oxidation). Biphasic oxidations with methyltrioxorhenium (e. g., to epoxides) are reviewed in Section 3.3.13 [244 i]. 

Substitutions. Etherification of phenols with alkylating agents, a base, and phase transfer catalyst in dry media under microwave irradiation can be an effective method. For preparation of alkyl azides from alkyl bromides one can use surfactant pillared clays as catalyst. ... 

Transformation of epoxides (238) into thiiranes (239) are first carried out in the presence of potassium thiocyanate in the absence of both solvent and phase-transfer catalysts (Equation (37) and Tables 38 and 39). 

Further studies showed that using a combination of sonication and phase-transfer catalyst (PTC) the rate and yield of the reaction of alkene with dichlorocarbene which resulted from chloroform and sodium hydroxide pellets in situ could be improved efficiently [40], Compared with the results reported by Regen [41 ] where sonication alone was used, they found that mechanical stirring was not necessary under high-power sonication. Other findings included the fact that the ratio of NaOHialkene could be decreased from 10 1 to 3 1 and the reaction period could be shortened from 5 h to 10—15 min in the presence ofO. 1-0.05% PTC. 

Table21. 2-Amino-l,l-dichlorocyclopropanesfromEnamines,Chloroform, Base and Phase-Transfer Catalyst...

A large number of chemical devulcanization agents for natural and synthetic rubbers have been developed. These include phosphines and phosphates, numerous sulfides and mercaptans, metal salts such as methyl iodide, phenyl lithium, lithium aluminum hydride, and phase-transfer catalysts. ... 

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