Chloride benzyltriethylammonium

Pha.se-Tra.nsfer Ca.ta.lysts, Many quaternaries have been used as phase-transfer catalysts. A phase-transfer catalyst (PTC) increases the rate of reaction between reactants in different solvent phases. Usually, water is one phase and a water-iminiscible organic solvent is the other. An extensive amount has been pubHshed on the subject of phase-transfer catalysts (233). Both the industrial appHcations in commercial manufacturing processes (243) and their synthesis (244) have been reviewed. Common quaternaries employed as phase-transfer agents include benzyltriethylammonium chloride [56-37-17, tetrabutylammonium bromide [1643-19-2] tributylmethylammonium chloride [56375-79-2] and hexadecylpyridinium chloride [123-03-5]. 

Benzyltriethylammonium chloride [56-37-1] is the most widely used catalyst under strongly basic conditions. Methyltrioctylammonium chloride [5137-55-3] (Ahquat 336, Adogen 464) is probably the least expensive catalyst. Others of high activity and moderate price are tetra- -butylammonium chloride [1112-67-0] bromide [1643-19-2] hydrogen sulfate [32503-27-8], tetra- -butylphosphonium chloride [2304-30-5], and other phosphonium salts of a similar number of C atoms. Many other onium salts can also be utilized. 

The highest yields in the Ciamician-Dennstedt reaction have been achieved using phase transfer catalysts (Table 8.3.1). In the reaction, the pyrrole or indole and a phase transfer catalyst (PTC, in this case benzyltriethylammonium chloride) are dissolved in chloroform and aqueous sodium hydroxide is added. Yields are typically in the 40s to 60s (rather than in the 20s for a typical Ciamician-Dennstedt reaction). More recently, yields as high as 80% have been reported using tetra-n-butylammonium hydrogen sulphate as the phase transfer catalyst. ... 

In the condensation reaction between chloro- and bromo-methyl aryl sulfones and carbonyl compounds, a-sulfonyloxiranes were obtained. In this condensation reaction, bases such as potassium t-butoxides372, NaH373 and aqueous concentrated hydroxide with benzyltriethylammonium chloride under two-phase condensation were used374. In the reaction with aldehydes only the trans-epoxide isomers resulted, whereas lith-iofluoromethyl phenyl sulfone 289375 and 291376 were found to add to aldehydes affording /J-hydroxysulfones 290 and 292, respectively. 

Benzyltriethylammonium chloride is available from Fisher Scientific Company. The preparation of this reagent is described in Org. Syn., 55, 97 (1975). 

Benzyltriethylammonium chloride is available from Eastman Organic Chemicals. The checkers prepared the salt in a state of high purity by a modification of a reported procedure.3 A solution of 33.7 g. (0.33 mole) of triethylamine and 50.0 g. (0.40 mole) of benzyl chloride (both from Eastman Organic Chemicals) in 60 ml. of absolute ethanol was refluxed for 64 hours. The solution was cooled to room temperature and 300 ml. of ether was added. The precipitated ammonium salt was removed by filtration, redissolved in the minimum amount of hot acetone, and reprecipitated with ether. 

Dehmlow and Klauck (1994) have shown how O- vs C-alkylations of 2-naphtholate, with benzyl bromide in toluene, in solid-liquid mode can be influenced by the PT catalyst (benzyltriethylammonium chloride) concentration. The ratio of O- to C-alkylated product could be varied from 0.02 to 7.5 depending on the catalyst concentration, temperature, etc. 

Another synthetic route to 3-methylhasubanan (43), proposed by Lattes et al. (74), consists of the intramolecular aminomercuration (75) of amino-ethylphenanthrene 27. The key intermediate 27 was treated with mercury(II) acetate in THF/water to yield 9-acetoxymercury-3-methoxyhasubanan (46), as depicted in Scheme 3, and then the reaction product 46 was successively treated with benzyltriethylammonium chloride, sodium hydroxide, and sodium borohydride to furnish the target, 3-methylhasubanan (43) (74). 

Cationic accelerants vary in their efficacy [161]. Other types of accelerant have also been evaluated. In one study [162], comparisons were made between tetra-ethylammonium bromide, benzyltriethylammonium chloride, polyfdiallyldimethylammonium chloride) and the diethyldimethylammonium derivative of a benzenesulphonate polyglycol ester. It was found that the cationic polymers had a greater effect than the simple quaternary ammonium compounds of lower molecular mass. This effect was attributed to the capability of the polymers to enter into hydrophobic interaction with the fibre surface. Ethylenediamine has also been found to accelerate the alkaline hydrolysis of polyester [163]. 

All the above chlorogermanes and chlorogermasilanes can be reduced by LLAIH4 in tetraline in the presence of benzyltriethylammonium chloride as a catalyst, providing germanes or silagermanes265. 

For example, direct treatment of red phosphorus with potassium hydroxide in a mixture of dioxane and water with a phase-transfer catalyst (benzyltriethylammonium chloride) allows direct reaction with primary haloalkanes to form the trialkylphosphine oxide in moderate (60-65%) yield.1415 Allylic and benzylic halides are similarly reported to generate the corresponding tertiary phosphine oxides. When the reaction is performed with a,(o-dihalides, cyclic products are generated only with four- and five-carbon chains the third site... 

In the ring closure of 5-amino-2,3-dihydro-17/-l,2,4-triazolo-3-thione 431 (R = NH2) with 1,2-dibromoethane in the presence of sodium methoxide (2equiv), compound 42 was formed as the main product (Scheme 50) <2003JHC821>. Similarly, the same type of functionalized thiazolo[3,2-A][l,2,4]triazoles 440 and 441 were isolated in the reaction of 1,2-dibromoethane with 2,3-dihydro-17/-l,2,4-triazolo-3-thione (431, R = H) or 2,3-dihydro-5-methyl-l/7-l,2,4-triazolo-3-thione (431, R = Me), using DMF as the solvent in the presence of potassium carbonate and benzyltriethylammonium chloride (CBTEA) (Scheme 50) <2004PS(179)1799>. 

The following quaternary ammonium salts are used as phase transfer catalyst tetra-K-butylammonium chloride (TBAC), tetra-n-butylammonium bromide (TBAB), benzyltriethylammonium chloride (BTEAC), and benzyltriethylammo-nium bromide (BTEAB). Chlorinated hydrocarbons, such as dichloromethane (DCM), chloroform (CF), tetrachloromethane (TCM), 1,2-dichloromethane (DCE), and nitrobenzene (NB) are used as solvents. The effects of phase-transfer catalyst and solvent on the yield and reduced viscosity are summarized in Table 9.1. 

Methyl 2,3-epoxypropanoate can be prepared by reaction of potassium glycidate with dimethyl sulfate and one equivalent of benzyltriethylammonium chloride in methylene chloride at room temperature (65% yield).14 The reactions of this ester with organolithium or organomagnesium reagents at low temperature afford optically pure epoxy ketones14 that may be transformed via reductive amination to anti amino epoxides.15... 

Benzyltriethylammonium chloride Ammonium, benzyltriethyl-, chloride (8) Benzenemethanaminium, N,N,N-triethyl-, chloride (9) (56-37-1)... 

The preparation of phosphoramidates from dialkyl phosphites, using the Todd-Atherton procedure, has been carried out in two-phase systems containing a phase-transfer agent, for example benzyltriethylammonium chloride, at 5 mole % concentration.84... 

Quaternary ammonium salts are generally stable under neutral or acidic conditions up to 150°C, but decomposition can occur with the quaternary ammonium ion acting as an alkylating agent in its reaction with anions (Scheme 1.1). Soft nucleophiles, such as RS, are more reactive with tetra-n-butylammonium bromide and benzyltriethylammonium chloride, although the latter salt also C-benzylates phenyl-acetonitrile under basic conditions [46], These side reactions are considerably slower than the main catalysed reactions with, for example, a haloalkane and the amount of unwanted impurity in the final alkylated product is never greater than the amount of catalyst used (i.e. generally > 2%). Harder anions, e.g. R2N and RO, rarely react with the ammonium salts. 

Hydrogen bromide, trimethylsilyl bromide and acetyl bromide have all been proven to be suitable bromide transfer agents [e.g. 12, 13]. Tetra-n-butylammonium salts catalyse the interconversion of dichloroalkanes into bromochloroalkanes and chloroiodoalkanes upon reaction with an excess of bromo- and iodobutane, respectively [14]. Similarly, mixed bromochloromethanes are obtained from the reaction of dibromochloromethane with benzyltriethylammonium chloride under basic conditions [15]. 

The reductive formation of C-S bonds via the reaction of carboxylic acids with phosphorus pentasulphide and red phosphorus has been utilized in the synthesis of 3-arylthiophenes starting from 2-arylsuccinic acids [66, 67]. The reaction is catalysed by benzyltriethylammonium chloride, but it has been suggested that co-catalysis with 18-crown-6 is advantageous [67]. 

A -(4-Toluenesulphonyl)sulphilimines, which are useful precursors in the synthesis of oxiranes and in alkylidene transfer reactions, have been prepared under solidiliquid phase-transfer catalytic conditions from Chloramine-T [2], Comparable yields are obtained irrespective of whether the reaction is catalysed by Adogen or by benzyltriethylammonium chloride (Table 4.31). The procedure is an improvement on the liquiddiquid two-phase method [3]. 

It is noteworthy that benzyltriethylammonium chloride is a slightly better catalyst than the more lipophilic Aliquat or tetra-n-butylammonium salts (Table 5.2). These observations obviously point to a mechanism in which deprotonation of the amine is not a key catalysed step. As an extension of the known ability of quaternary ammonium halides to form complex ion-pairs with halogen acids in dichloromethane [8], it has been proposed that a hydrogen-bonded ion-pair is formed between the catalyst and the amine of the type [Q+X—H-NRAr] [5]. Subsequent alkylation of this ion-pair, followed by release of the cationic alkylated species, ArRR NH4, from the ion-pair and its deprotonation at the phase boundary is compatible with all of the observed facts. 

A similar intramolecular cyclization of 3-arylamino-2-chloropropanonitriles under basic conditions to yield l-aryl-2-cyanoaziridines (Scheme 5.2) also proceeds more smoothly when benzyltriethylammonium chloride is added to the reaction mixture [20], The procedure is not suitable, however, for the preparation of /V-alkyl analogues. 

Alkylation of the more acidic hydrazo [25] and triazene [26] systems proceeds readily under liquiddiquid two-phase conditions, using tetra-n-butylammonium hydroxide and benzyltriethylammonium chloride, respectively, as the catalysts (Tables 5.5 and 5.6). 

A two-phase modification of the traditional Atherton-Todd phosphorylation reaction (Table 5.8) is aided by the addition of benzyltriethylammonium chloride [36,37]... 

The analogous reaction of benzyl and butyl naphthylcarbamates and of benzyl phenylcarbamates has been carried out in good yield under both liquiddiquid and solidrliquid two-phase conditions, using benzyltriethylammonium chloride as the catalyst [16, 17]. A similarly catalysed /V-alkylation of the ethyl carbamic esters derived from 1,2-diaminobenzene is reported [17] to lead to the formation of 1,3-dialkylbenzimidazol-3-ones (Scheme 5.7). 

It can be assumed that the azoles are deprotonated by the interfacial exchange mechanism, but it is noteworthy that it has been suggested that the rate of alkylation of indole under liquiddiquid two-phase conditions decreases with an increase in the concentration of the sodium hydroxide [8]. The choice of catalyst appears to have little effect on the reaction rate or on the overall yields of alkylated azole. Benzyltriethylammonium chloride, Aliquat, and tetra-n-butylammonium hydrogen sulphate or bromide have all been used at ca. 1-10% molar equivalents (relative to the concentration of the azole) for alkylation reactions, but N-arylation of indole with an activated aryl halide requires a stoichiometric amount of the catalyst [8]. 

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