Methyl -, tetraethylammonium

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). ... 

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. 

The application of phase-transfer catalysis to the Williamson synthesis of ethers has been exploited widely and is far superior to any classical method for the synthesis of aliphatic ethers. Probably the first example of the use of a quaternary ammonium salt to promote a nucleophilic substitution reaction is the formation of a benzyl ether using a stoichiometric amount of tetraethylammonium hydroxide [1]. Starks mentions the potential value of the quaternary ammonium catalyst for Williamson synthesis of ethers [2] and its versatility in the synthesis of methyl ethers and other alkyl ethers was soon established [3-5]. The procedure has considerable advantages over the classical Williamson synthesis both in reaction time and yields and is certainly more convenient than the use of diazomethane for the preparation of methyl ethers. Under liquidrliquid two-phase conditions, tertiary and secondary alcohols react less readily than do primary alcohols, and secondary alkyl halides tend to be ineffective. However, reactions which one might expect to be sterically inhibited are successful under phase-transfer catalytic conditions [e.g. 6]. Microwave irradiation and solidrliquid phase-transfer catalytic conditions reduce reaction times considerably [7]. 

The only exception to this statement (outside of the triphenylmethyl methacrylate case) in the literature up to now concerns the polychloral obtained in the presence of tetraethylammonium 0-methyl- or O-acetylmandelate (366-368). The monomer was treated so as to give directly a polymeric film that is endowed with extremely high rotatory power ([a]o exceeding —1800°, but preliminary data obtained with other initiators led the authors to suppose that values > 3000° could be attained). 

RuCoO,SC Ruthenium, nonacarbonyl-p.,-thio-dicobalt-, 26 352 RuCo2OuCi, Ruthenium, undecacar-bonyldicobalt-, 26 354 RuCojNOi2C 2H2(i, Ruthenate(l -), dodeca-carbonyltricobalt-tetraethylammonium, 26 358 RuF12N4P2C (,H24, Ruthenium(II), tetrakis-(acetonitrile) (n4-1,5-cyclooctadiene)-bis[hexafluorophosphate(l -)], 26 72 RuF 2NBP2Ci2H36, Ruthenium(II), (V cyclooctadiene)tetrakis(methyl-hydrazine)-... 

Jacobsen and Pedersen153 confirmed the generation of benzoxonium ion 126 by treatment of compound 125 with triphenylmethyl fluoroborate in acetonitrile, but they treated it with tetraethylammonium bromide, obtaining a 3 2 mixture of the a and /3 anomers of methyl 2,5-di-0-benzoyl-3-bromo-3-deoxy-D-xylofuranoside (134) in a yield of 74%. This mixture could be anomerized to give the pure )8 anomer (overall yield 60%) by treatment with hydrogen bromide followed by the action of methanol. 

A different route to pyrones is the preparative electrochemical oxidation of enamines in acetonitrile in the presence of tetraethylammonium perchlorate (88MI2) (Scheme 46). The synthesis of 2-pyrone derivatives has been carried out by reaction of /3-dicarbonyl compounds with methyl-a-benzoylamino-/3-dimethylaminoacrylate (96JHC751). Thiapyran derivatives can be obtained by interaction of enamines based on (/3-amino-a-cyanoacryloylmethyl)pyridinium chloride derivatives with carbon disulfide (95M711).The synthesis of pyridine derivatives based on analogous enamines has been described as well (95M711). 

Protecting groups were removed by treatment of the polymer with sodium methoxide in p-dioxane, followed by tetraethylammonium hydroxide. Although nitrogen-free polymers were obtained by this procedure, the polymers had suffered a 16-20% decrease in PH. The resulting polymers were insoluble in water, sodium hydroxide, N, -dimethylformamide, and methyl sulfoxide, but were soluble in tetraethylammonium hydroxide and in Schweizer reagent. 

As further evidence of the importance of hydrophobic interactions in these systems, we examined the partition coefficient of methyl orange in the presence of water structure-forming and water structure-breaking salts above and below the transition temperature [70], Methyl orange is an easily detected, hydro-phobic dye which has been sulfonated to improve water solubility. Water structure-breaking salts like tetraethylammonium chloride (TEAC) are known to minimize hydrophobic interactions while water structure-forming salts like ammonium sulfate are known to increase hydrophobic interactions [165, 166]. 

The 2-benzazepin-3-ones 259 have been made in moderate yields by sequential intramolecular acid-catalyzed addition followed by thiol elimination from the precursor phenylsulfanylacrylamides 258 (Scheme 33). The acrylamides 258 were prepared from reaction of the benzylamines 255 with the PNB-ester 256 to give the amides 257, and then N-methylation with Mel in the presence of potassium hydroxide and tetraethylammonium bromide, as a phase-transfer catalyst. Other noncyclized products were also observed depending on the structure of the A-aryl methyl group in 258 and on the nature of the solvent <2002H(57)1063>. 

Diethyl-1 -methyl-1 -methoxyethylammonium Tributyl-methylammonium Trimethyl-n-hexylammonium Tetraethylammonium Triethyl-hexylammonium Tetrabutylammonium Triethyl-hexylammonium Hydroxyethyl-trimethylammonium Butyl-diethyl-methylammonium ... 

Most of the salts are hydrolyzed in moist air but are stable indefinitely in a dry nitrogen atmosphere. A notable exception is tetraethylammonium hexabromotantalate(V), which is quite stable in the atmosphere and is only slowly hydrolyzed by concentrated aqueous ammonia. Complete hydrolysis is more readily achieved by the addition of acetone followed by aqueous ammonia, the mixture being gently warmed on a water bath. They are generally insoluble in nonpolar or slightly polar solvents but are fairly soluble in more polar solvents such as acetonitrile (methyl cyanide) in the latter solvent the solutions show the expected molar conductivities. 

One of the chlorides in this complex can be exchanged for perchlorate on treatment of a solution of the complex in dichloromethane/acetonitrile with silver perchlorate2. Dicarbonyl(chloromethylidyne)[hydrotris(pyrazol-l-yl)borato]molybdenum(IV) reacted with sodium telluride in aqueous methanol to produce the anionic dicarhonyl[hydro-tris(pyrazol-l-yl)borato telluracarbonylmolybdate(0), which was isolated as the moderately air-stable tetraethylammonium salt. This salt reacted with methyl iodide in acetonitrile to form dicarbonyl[hydrotris(pyrazolo)borato](methyltelluromethylidyne) molybdenum(IV)3. 

By using the ammonium ions with four alkyl groups larger than the methyl group, the other types of silicate anions with cage-like structures are formed. For example, in tetraethylammonium (N+(C2H3) ) silicate aqueous solutions, the prismatic hexameric silicate anion (SigO g, prismatic hexamer) is formed (13,14,17,18). 

Tellurate(IV) Methyl-tetrachloro-(Tetraethylammonium) E12h, 361 (from R—TeCl3)... 

Cerrai et al. carried out an interesting study of the electropolymerisation of isobutyl vinyl ether with tetrabutylammonium triiodide in methyl chloride. Form the electrolysis of the supporting salt alone and the kinetics of the anodic initiated polymerisation it was clearly proved that nmlecular todine was the catalyst responsible for the process. Recently, Breitenbach et al. published an investigation of the anodic initiators cationic polymerisation of isobutyl vinyl ether. The background electrolyte was tetraethylammonium perchlorate and the solvent a mixture of acetonitrile and... 

Abbreviations conform to Tarr s nomenclature F, formic acid A, acetic acid fA, trifluoroacetic acid KNm, dimethylformamide mSO, methylsulfoxide MOH, methanol EOH, ethanol MCN, acetonitrile M5KN, N-methyl-pyrrolidone 6N, pyridine N, ammonia ENm, dimethylethylamine M6N, N-methylpiperidine M6NO, N-methylmorpholine E6NO, N-ethylmorpholine ENip, diisopropylethylamine eN, triethylamine fmK, hexafluoroacetone (hydrate) cit, citric acid W, water NaA, sodium acetate eN+, tetraethylammonium MNT, methylthiocarbamyl NT, phenylthiocarbamyl MNGS, methylisothiocyanate ONCS, phenylisothiocyanate NPN-TNdab, N-aminopropyl-N -p-dimethylaminoazobenzene thiourea. 

Thiazole A -oxides can easily be alkylated on the oxygen. For example, Ar-(alkoxy)-5-(p-methoxyphenyl)-4-methylthiazole-2(377)-thiones were prepared from Ar-(hydroxy)-5-( -methoxyphenyl)-4-methylthiazole-2(3//)-thione tetraethylammonium salt and an appropriate alkyl chloride or tosylate in moderate to good yields <20060BC2313>. A -Methoxythiazole-2(377)-thiones were synthesized from the A -hydroxythiazole-2(3//)-thiones by treatment first with a tetraalkylammonium hydroxide in methanol and then methyl ra-toluenesulfonate in DMF <2005EJ0869>. 

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