Benzyltriethylammonium chloride, as phase

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). 

Complexes of other metals are also capable of catalyzing useful carbonylation reactions under phase transfer conditions. For example, certain palladium(o) catalysts, like Co2(C0)g, can catalyze the carbonylation of benzylic halides to carboxylic acids. When applied to vinylic dibromides, unsaturated diacids or diynes were obtained, using Pd(diphos)2[diphos l,2-bis(diphenylphosphino)ethane] as the metal catalyst, benzyltriethylammonium chloride as the phase transfer agent, and t-amyl alcohol or benzene as the organic phase(18),... 

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. 

Michael addition to a, -unsaturated aldehydes The Michael addition of malonic ester and acetoacetic ester to a,0-unsaturated aldehydes can be carried out in moderate yields under phase-transfer conditions with sodium or potassium carbonate as base and benzyltriethylammonium chloride as catalyst (equation I). 

Acetates and benzoates of unbranched aldehyde enols react with chloroform in a phase-transfer catalytic system, with benzyltriethylammonium chloride as a catalyst, to form mainly or exclusively products of trichloromethyl anion addition (however, vinyl pivalate under these conditions forms the dichlorocarbene addition product almost exclusively). ... 

The synthesis of 1,1-diiodocyclopropane is carried out via addition of diiodocarbene (car-benoid) to alkenes the carbene, in turn, is generated from iodoform and a base. The process is realized using phase-transfer catalysis,(33% or 50%aqueous sodium hydroxide and a quaternary ammonium salt, typically benzyltriethylammonium chloride, as a catalyst) or in the presence of potassium ter/-butoxide in /ert-butyl alcohol 25,127,128 g... 

Dichlorocyclopropanes have been converted to l,l-bis(phenylsulfanyl)cyclopropanes in good yield under phase-transfer conditions using sodium hydroxide as base, benzene as organic solvent, and tetrabutylammonium bromide or benzyltriethylammonium chloride as catalyst. Typically, ler/-butyl 2,2-bis(phenylsulfanyl)cyclopropanecarboxylate (3) was obtained in 71 /o yield from tert-butyl 2,2-dichlorocyclopropanecarboxylate by this method. ... 

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]. 

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. 

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. 

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. 

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). 

Benzyltriethylammonium chloride is frequently used as the phase-transfer catalyst, but it has been noted that the catalyst itself produces phenylacetic acid under the carbonylation conditions [6]. Trimethyl(phenyl)ammonium chloride and tetra-n-butylammonium chloride both catalyse the reaction efficiently. 

An intriguing use of a quaternary ammonium salt in a two-phase reaction is to be found with the regeneration of 1 -benzyl-1,4-dihydronicotinamide by sodium dithionite in a biomimetic reduction of thiones to thiols [12], The use of sodium dithionite in the presence of sodium carbonate for the 1,4-reduction of the pyri-dinium salts to 1,4-dihydropyridines is well established but, as both the dithionite and the pyridinium salts are soluble in water and the dihydropyridine and the thione are insoluble in the aqueous phase and totally soluble in the organic phase, it is difficult to identify the role of the quaternary ammonium salt in the reduction cycle. It is clear, however, that in the presence of benzyltriethylammonium chloride, the pyridine system is involved in as many as ten reduction cycles during the complete conversion of the thione into the thiol. In the absence of the catalyst, the thione is recovered quantitatively from the reaction mixture. As yet, the procedure does not appear to have any synthetic utility. 

Isomerization of allylic alcoholsAllylic alcohols can be isomerized to carbonyl compounds by several organometallic reagents at elevated temperatures. The reaction can be conducted at 25-30° overnight with [Rh(CO)2Cll2 under phase-transfer conditions. Cleaner reactions obtain if benzyltriethylammonium chloride is used as catalyst. 

Morris Jr. and Kiely37 in 1987 noted a great acceleration in the oxidation of alcohols, with catalytic Ru04 in a biphasic system, upon addition of 1% molar benzyltriethylammonium chloride (BTEAC) as a phase-transfer catalyst. 

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