[56-37-1] · C13H22ClN · Benzyltriethylammonium Chloride · (MW 227.81)
(phase transfer catalyst1)
Alternate Names: TEBA; TEBAC.
Physical Data: mp 185 °C (dec).
Solubility: sol acetone, alcohol, H2O, 1% aq. NaOH; insol ether, 20% aq. NaOH.
Form Supplied in: anhydrous white solid; monohydrate also available.
Analysis of Reagent Purity: tetraalkylammonium salts can be titrated with potassium 3,5-di-t-butyl-2-hydroxybenzenesulfonate and iron(III) chloride.1a
Preparative Method: via the reaction of Benzyl Chloride with Triethylamine in absolute ethanol.2
Purification: precipitation from acetone with ether.2
Handling, Storage, and Precautions: highly hygroscopic.
Benzyltriethylammonium chloride is one of many commonly used phase transfer catalysts. Although in specific reactions other phase transfer catalysts have proven superior,3 TEBA remains the reagent of choice for many reactions.
TEBA has been used extensively in the formation of carbenes in heterogeneous systems. Dichlorocarbene2,4 is formed from Chloroform and aqueous Sodium Hydroxide in the presence of TEBA (eq 1).4a Dibromocarbenes can also be generated using TEBA.4b,4d TEBA has been used as a means of introducing hydroxide or carboxylate ion in alkylations of nitriles,5 cyanohydrins,6 Schiff bases,7 sulfones,8 malonates,9 and benzyl ketones.10 Michael addition reactions11 have been catalyzed by TEBA, as well as the condensation of O-benzoyl cyanohydrins,12 malonitrile,13 and sulfones14 with benzaldehyde. Condensation of 3-methyl-5-pyrazolone with Carbon Disulfide and alkyl bromides was realized under phase transfer conditions using TEBA.15
TEBA has been used in the alkylation of trifluoroacetamide with a-bromo esters to form, after hydrolysis, a-amino acids (eq 2).16 TEBA has also been used in the nitration of aromatics,17 the alkylation of secondary amides,18 and the dehydration of ureas to form carbodiimides.19 Reaction of thioamides with dibromoethane and sodium hydroxide catalyzed by TEBA gives thiazolidines.20
Benzyl21 ethers have been formed using TEBA catalysis. TEBA has been used in a variety of oxidation reactions, including permanganate oxidation of longifolene22 and benzaldehyde,23 a-hydroxylation of benzyl nitriles giving phenyl ketones,24 and Ruthenium(VIII) Oxide catalyzed oxidations of secondary alcohols to ketones with Sodium Periodate.25
TEBA facilitates the solubilization of organic acids, permitting formation of a diacid chloride from an insoluble diacid (eq 3).26 Organic peroxy acids can also be prepared from the corresponding acid using TEBA and potassium persulfate.27
TEBA has been used in the formation of phosphorodiamidates from bis(dimethylamino) phosphorochloridate28 and phosphate esters29 or phosphoramidates30 from Diethyl Phosphonite. Di-t-butyl phosphorohalidates have been prepared from di-t-butyl phosphite using TEBA, carbon tetrachloride and aq. NaOH.31
TEBA has proven very effective in the formation of metal hydrides under phase transfer conditions;32 for example, (Ph3P)3RuHCl and (i-Pr3P)2IrHCl2 are converted to (Ph3P)3RuH2(H)2 and (i-Pr3P)2IrH5,32a respectively, upon reaction with hydrogen and aq. NaOH/benzene with TEBA. In metal carbonyl chemistry, TEBA has been used as a phase transfer catalyst.33 TEBA has also been used in the dibromination of alkenes34 and azide transfer reactions.35 Selective tosylation of adenosine has been achieved using Di-n-butyltin Oxide, p-Toluenesulfonyl Chloride, and TEBA (eq 4).36
Paul B. Savage
The Ohio State University, Columbus, OH, USA