Tetraethylammonium

Fig. V-5. The repulsive force between crossed cylinders of radius R (1 cm) covered with mica and immersed in propylene carbonate solutions of tetraethylammonium bromide at the indicated concentrations. The dotted lines are from double-layer theory (From Ref. 51).

Methyl, ethyl, and benzyl ethers have been prepared in the presence of tetraethylammonium fluoride as a Lewis base (alkyl halide, DME, 20°, 3 h, 60-85% yields). ... 

Tetraethylammonium bromide [71-91-0] M 210.2, m 269 (dec), 284 (dec). Recrystd from EtOH, CHCI3 or diethyl ether, or, recrystd from acetoniuile, and dried over P2O5 under reduced pressure for several days. Also recrystd from EtOH/diethyl ether (1 2), EtOAc, water or boiling MeOH/acetone (1 3) or by adding equal volume of acetone and allowing to cool. Dried at 100 in vacuo for 12 days, and stored over P2O5. 

Tetraethylammonium chloride hydrate [56-34-8] M 165.7, m dec>200 . Crystd from EtOH by adding diethyl ether, from warm water by adding EtOH and diethyl ether, from dimethylacetamide or from CH2CI2 by addition of diethyl ether. Dried over P2O5 in vacuum for several days. Also crystd from acetone/CH2Cl2/hexane (2 2 1) [Blau and Espenson J Am Chem Soc 108 1962 1986 White and Murray J Am Chem Soc 109 2576 1987]. 

Tetraethylammonium iodide [68-05-3] M 257.2, m 302 , >300 (dec). Crystd from acetone/MeOH, EtOH/water, dimethylacetamide or ethyl acetate/EtOH (19 1). Dried under vacuum at 50° and stored over P2OS. 

Tetraethylammonium picrate [741-03-7] M 342.1, m >300 (dec). Purified by successive crystns from water or 95% EtOH followed by drying in vacuum at 70°. 

Tetraethylammonium tetraphenylborate [12099-10-4] M 449.4. Recrystd from aqueous acetone. Dried in a vacuum oven at 60° for several days. Similarly for the propyl and butyl homologues. 

A variety of media have been used for the Wallach fluorination reaction anhydrous hydrogen fluoride alone or with cosolvents such as methylene chloride, benzene, or tetrahydrofuran and hydrogen fluoride-pyridine alone or with co solvents such as benzene, glyme, or acetic acid [42,43, 46 50] Solutions of cesium fluoride, tetraethylammonium fluoride, or tetrabutylammonium fluoride in strong acids such as methanesulfonic acid or trifiuoroacetic acid with numerous cosolvents have also been studied [48, 49]... 

Compare electrostatic potential maps for tetrabenzyl-ammonium ion and tetraethylammonium ion with that of benzyltrimethylammonium ion. Are they likely to be as effective or more effective as phase-transfer catalysts as benzyltrimethylammonium ion Explain. (Hint Predict solubility properties for the three ions.)... 

Chloro-3,4-dimethylthiazolium tetrafluoroborate with [Mn(CO)5] gives the carbene complex 19 (74JCS(D)760). The product reacts with tetraethylammonium iodide to give the cM-neutral complex 20. 

The first example of homogeneous transition metal catalysis in an ionic liquid was the platinum-catalyzed hydroformylation of ethene in tetraethylammonium trichlorostannate (mp. 78 °C), described by Parshall in 1972 (Scheme 5.2-1, a)) [1]. In 1987, Knifton reported the ruthenium- and cobalt-catalyzed hydroformylation of internal and terminal alkenes in molten [Bu4P]Br, a salt that falls under the now accepted definition for an ionic liquid (see Scheme 5.2-1, b)) [2]. The first applications of room-temperature ionic liquids in homogeneous transition metal catalysis were described in 1990 by Chauvin et al. and by Wilkes et ak. Wilkes et al. used weekly acidic chloroaluminate melts and studied ethylene polymerization in them with Ziegler-Natta catalysts (Scheme 5.2-1, c)) [3]. Chauvin s group dissolved nickel catalysts in weakly acidic chloroaluminate melts and investigated the resulting ionic catalyst solutions for the dimerization of propene (Scheme 5.2-1, d)) [4]. 

As early as 1972 Parshall described the platinum-catalyzed hydroformylation of ethene in tetraethylammonium trichlorostannate melts [1]. [NEt4][SnCl3], the ionic liquid used for these investigations, has a melting point of 78 °C. Recently, platinum-catalyzed hydroformylation in the room-temperature chlorostannate ionic liquid [BMIM]Cl/SnCl2 was studied in the author s group. The hydroformylation of 1-octene was carried out with remarkable n/iso selectivities (Scheme 5.2-13) [66]. 

The Ugi reaction has been successfully applied to the synthesis of oligopeptide derivatives, c.g.. in the construction of a pure tetra-L-valine derivative69. The 2-methylpropanaldimine 2 of (/7)-l-ferroccnyl-2-rnethylpropylarnine with /V-formyl-L-2-amino-3-methylbulanoic acid (3) as the carboxylic acid component and methyl A/-[(.S)-2-isocyano-3-mcthyl-l -nxo-buLyl -L-2-aiuino-3-inethylbutanoate (4) furnishes the diastereomeric valyl-valyl-valyl-valine derivatives in a ratio (S,S[R],S,S)i(S,R[R],S,S) of 91 9. The stereoselectivity of the process can be enhanced to 98.5 1.5 when two equivalents of tetraethylammonium A -formylvalinate are added. 

FIGURE 2-11 Spectra for a series of applied potentials (mV vs. Ag/AgCl) during thin-layer spectroelectrochemical experiment on 1.04 x 10 3 M [Tc(III)(dmpe)2Br2]+. Medium is dimethylformamide containing 0.5 M TEAP = tetraethylammonium perchlorate. (Reproduced with permission from reference 27.)... 

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