Benzyltriethylammonium hydroxide

Phase transfer catalysis was found <90CCC597> to be successful for /V-substitution of the furo[3,2-6]pyrrole system. The reaction of furo[3,2-fe]pyrroles with lithium hydride in DMF furnished N-lithium derivatives, which gave jV-acetyl derivatives with acetyl chloride. The same compounds can be obtained by boiling in acetic anhydride. The treatment of furo[3,2-fe]pyrrole derivatives with acrylonitrile in pyridine in the presence of benzyltriethylammonium hydroxide gave 4-(2-cyano-ethyl)furo[3,2-6]pyrrole derivatives. Phase transfer catalysis has been employed for the preparation of variously substituted 4-phenylsulfonylfuro[3,2-ft]pyrroles and l-phenylsulfonylbenzo[fe]furo [3,2-/>]pyrroles <94CCC499>. 

Both benzyltriethylammonium chloride (1) and benzyltriethylammonium hydroxide (2) partition between the aqueous and organic phases. In the aqueous phase, the quaternary ammonium chloride (1) reacts with concentrated hydroxide to give the quaternary ammonium hydroxide (2). In the chloroform phase, 2 reacts with chloroform to give the tri-chloromethyl anion (3), which eliminates chloride ion to give dichlorocarbene, iCClj, (4), and 1. The carbene (4) reacts with the olefin to give product (5). 

Benzyltriethylammonium chloride functions as a phase-transfer catalyst. The chloride is soluble in the basic aqueous phase and is converted into benzyltriethylammonium hydroxide, soluble in the organic phase. The hydroxide ion reacts with chloroform to give dichlorocarbene with regeneration of benzyltriethylammonium chloride. 

The asymmetric intramolecular conjugate addition of amines to optically active a,p-unsaturated sulfoxides has been studied [111-115], For example, the (Rs)-(E)-a,P-unsaturated sulfoxide (141), upon basic hydrolysis with lithium hydroxide, gave a mixture of the diastereoisomeric isoquinolines (143) and (144) in the ratio 63 37, An enhanced diastereoselectivity was observed upon basic hydrolysis of the (i s)-(2)-a,P-unsaturated sulfoxide (142) with benzyltriethylammonium hydroxide, giving (143) and (144) in the ratio 16 84 (note that the major product... 

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. 

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). 

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... 

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). 

In contrast, liquidiliquid phase-transfer catalysis is virtually ineffective for the conversion of a-bromoacetamides into aziridones (a-lactams). Maximum yields of only 17-23% have been reported [31, 32], using tetra-n-butylammonium hydrogen sulphate or benzyltriethylammonium bromide over a reaction time of 4-6 days. It is significant that a solidiliquid two-phase system, using solid potassium hydroxide in the presence of 18-crown-6 produces the aziridones in 50-94% yield [33], but there are no reports of the corresponding quaternary ammonium ion catalysed reaction. Under the liquidiliquid two-phase conditions, the major product of the reaction is the piperazine-2,5-dione, resulting from dimerization of the bromoacetamide [34, 38]. However, only moderate yields are isolated and a polymer-supported catalyst appears to provide the best results [34, 38], Significant side reactions result from nucleophilic displacement by the aqueous base to produce hydroxyamides and ethers. 

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]. 

As indicated in Chapter 1, the hydroxide ion is not readily transported into the organic phase, particularly when the benzyltriethylammonium ion is employed as the catalytic cation. Hence, the reaction of chloroform with the hydroxide ion must occur by an interfacial mechanism. The interfacial reaction initially produces the trichloromethyl anion, which immediately forms an effective ion-pair with the benzyltriethylammonium cation. Diffusion of the ion-pair into the bulk of the organic phase occurs, followed by a slow decomposition of the trichloromethyl anion... 

A study of Hofmann vs Saytzeff elimination from 2-bromooctane under soliddiquid two-phase conditions [6] shows that the 1-octene 2-octene ratio depends not only on the base used, but also on the catalyst. Aliquat is the most effective catalyst giving a 98% overall yield with a l-octene 2-octene ratio of ca. 2 1. Benzyltriethylammonium chloride catalyses a 95% conversion with a ratio of ca. 3 1 in favour of the 1-octene. Potassium hydroxide and potassium t-butoxide favour the formation of 1-octene, whereas sodium methoxide and sodium ethoxide favour the formation of 2-octene [6]. 

Quaternary ammonium periodates, prepared either from periodic acid and the quaternary ammonium hydroxide [21, 22] or by metathesis from sodium periodate and a quaternary ammonium salt [e.g. 23-25], have been used for a range of oxidations at stoichiometric levels in two-phase systems [21-33], The tetra-n-butyl-ammonium and hexadecyltrimethylammonium salts are both highly soluble in organic solvents (considerably less so in water), whereas benzyltriethylammonium periodate has a lower solubility and stability than either salt. 

A. Dibromoearbene addition to (IR)-nopadiene. A 250-raL, three-necked flask is equipped with a mechanical stirrer, nitrogen Inlet, and serum cap. The flask is charged with 26.2 mL (0.30 mol) of bromoform (Note 1), 29.5 g (0.20 mol) of (IR)-nopadlene (Notes 2 and 3), 1.0 g (4.4 mmol) of benzyltriethylammonium chloride (TEBA), 0.8 mL of ethanol, and 20 mL of dichloromethane (Note 4). The suspension Is stirred and cooled In an Ice bath while 100 mL of 50t sodium hydroxide solution Is added over 10 min from a dropping funnel. The reaction mixture Is stirred at room temperature for 24 hr and poured into 250 mL of water. The lower layer Is separated and the... 

Tabushi and coworkers106 have reported that dichlorocarbene reacts very readily with alcohols to give the corresponding chlorides. Dichlorocarbene was generated by using an emulsifying system the method involves treatment of the alcohol with chloroform in the presence of an aqueous solution of sodium hydroxide and a catalytic amount of benzyltriethylammonium chloride. 

With soluble quaternary ammonium salts as catalysts the reaction is thought to take place at the aqueous/organic interface because a) the solubilities of quaternary ammonium hydroxides in organic solvents are too low to account for the observed reaction rates, and b) the most active catalysts are benzyltriethylammonium and... 

Schiff base 293 with dichlorocarbene, prepared from chloroform and potassium hydroxide in situ, in the presence of benzyltriethylammonium chloride afforded 2-chloro-3-phenyl-l //-pyrimido[l, 2-a]quinolin-l-one (294), l-chloro-2-phenylimidazo[l,2-a]quinoline, and l-(l-quinolyl)-2,2-dichloro-3-phenylaziridine in 5%, 8%, and 6% yields, respectively (91KGS810). 

Undoubtedly the most important and widely used procedure for the generation of dichlorocarbene involves the reaction of chloroform with aqueous sodium hydroxide under the conditions of phase transfer catalysis (PTC), introduced by Makosza.20-22 Under these conditions chloroform reacts with sodium hydroxide to form sodium trichloromethylide which on exchange with a quaternary ammonium salt, usually benzyltriethylammonium chloride, is converted to the unstable quaternary ammonium methylide which dissociates in the organic phase to give dichlorocarbene. The dichlorocarbene irreversibly adds to the alkene (Scheme 1). 

The phase-transfer technique is a simple and efficient tool for the benzylation of carbohydrates. With benzyltriethylammonium chloride or tetrabutylammonium bromide as a catalyst, a mixture of aqueous, 50 % sodium hydroxide and benzyl bromide or chloride in benzene or dichloromethane solution gives a good yield of the fully protected product [103, 104], such as methyl 2,3-di-0-benzyl-4,6-0-benzylidene c-D-glucopyranoside, when stirred at room temperature for several hours. The latter catalyst is slightly more efficient. Dichloromethane has been observed to produce methylene acetals from cis vicinal diols under comparable conditions [103]. 

Chloro-2,8-bis(trifluoromethyl)quinoline N,0-Dimethylhydroxylamine hydrochloride Benzyltriethylammonium chloride Sodium hydroxide... 

The catalytic approach to conjugate addition is illustrated by the addition of a (3-dike tone to an aromatic enone catalysed by potassium hydroxide and benzyltriethylammonium chloride, which is a phase transfer catalyst. Once again, the catalytic cycle is initiated by deprotonation of the most acidic component in the reaction mixture, acetyl acetone, which is followed by a cycle of conjugate addition and proton exchange leading inexorably to the product. 

The only reported generation of fluoroiodocarbene involves the treatment of fluoro-diiodomethanc with sodium hydroxide in a two-phase system with benzyltriethylammonium chloride as a phase-transfer agent. Although a good yield of the fluoroiodocyclopropanc is obtained when fluoroiodocarbene is generated in the presence of styrene, with more sterically erowded substrates and unconjugated alkcnes the yields are low. 

To a mixture of 8.2 g of cyclohexene, 12.0 g of chloroform caution ), and 20 mL of 50% aqueous sodium hydroxide in a 125-mL Erlenmeyer flask containing a thermometer, add 0.2 g of benzyltriethylammonium chloride. Swirl the mixture to produce a thick emulsion. The temperature of the reaction will rise gradually at first and then markedly accelerate. As it approaches 60°C prepare to immerse the flask in an ice bath. With the flask alternately in and out of the ice bath, stir the thick paste and maintain the temperature between 50 and 60°C. After the exothermic reaction is com-... 

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