Triethylammonium halide

In the reaction of Q,/3-unsaturated ketones and esters, sometimes simple Michael-type addition (insertion and hydrogenolysis, or hydroarylation, and hydroalkenylation) of alkenes is observed[53,54]. For example, a simple addition product 56 to methyl vinyl ketone was obtained by the reaction of the heteroaromatic iodide 55[S5]. The corresponding bromide affords the usual insertion-elimination product. Saturated ketones are obtained cleanly by hydroarylation of o,/3l-unsaturated ketones with aryl halides in the presence of sodium formate, which hydrogenolyses the R—Pd—I intermediate to R— Pd—H[56]. Intramolecular hydroarylation is a useful reaction. The diiodide 57 reacts smoothly with sodium formate to give a model compound for the afla-toxin 58. (see Section 1.1.6)[57]. Use of triethylammonium formate and BU4NCI gives better results. 

Formate is an excellent hydride source for the hydrogenolysis of aryl halides[682]. Ammonium or triethylammonium formate[683] and sodium formate are mostly used[684,685]. Dechlorination of the chloroarene 806 is carried out with ammonium formate using Pd charcoal as a catalyst[686]. By the treatment of 2,4,6-trichloroamline with formate, the chlorine atom at the /iiara-position is preferentially removed[687]. The dehalogenation of 2,4-diha-loestrogene is achieved with formic acid, KI, and ascorbic acid[688]. 

Carbonylation of Halides - Pd(tppts)3-catalysed carbonylation of bromo-benzene (Equation 7) in the presence of NEt3 in an aqueous/toluene (1/1) two phase system at 150°C and 15 bar CO afforded the triethylammonium salt of benzoic acid (100% yield).464,465 Rates were rather low (TOF s of 3.3-17 h ) but no decomposition of Pd(tppts)3 (tppts/Pd 12.5) was observed and the catalyst could be recovered quantitatively and recycled 464 However, in a second recycle extensive decomposition of the catalyst occurred with formation of palladium black. Generally in carbonylation reactions of halides the formation of stoichiometric amounts of either HX or halide salts still remains a problem of environmental concern despite the attractiveness due to the presence of the aqueous solvent. 

Ostrovskii et al. <1996MC24> described an unusual acylation reaction of tetrazole triethylammonium salts 231 bis(5-phenyltetrazol-2-yl)acetone 257 was obtained by interaction of various tetrazole triethylammonium salts 231 with 5-phenyl-2-tetrazolylacetyl chloride 256. The mechanism of the reaction is suggested to include a heterolysis of the iV-acyl intermediate resulting in acyl cation formation followed by transacylation of the methylene group in the second molecule of the acyl halide (Equation 40) <1996MC24>. 

Polyesters have been synthesized by the reaction of glycols with the diammonium or bis(triethylammonium) salts or fV-methylpyrrolidone complexes of dibasic acids. Dicarboxamides or dinitriles also react with glycols to form polyesters. Alkylene halides and salts of terephthalic acid react to give polyesters. In general, however, all these reactions give low-molecular-weight products, and no kinetic studies have been made. 

The first attempt at a nucleophilic substitution reaction in an ionic liquid was carried out by Ford and coworkers [124-126]. Here, the rates of reaction of halide ion (in the form of its triethylammonium salt) with methyl tosylate in the molten salt triethylhexylammonium triethylhexylborate were studied (Scheme 5.2-56). This was compared with similar reactions in dimethyl formamide (DMF) and methanol. The reaction rates in the molten salt appeared to be intermediate in rate between methanol and DMF (a dipolar aprotic solvent known to accelerate Sn2 substitution reactions). 

Higher alkyl or aryl esters are prepared either by reaction of [ C]acetyl chloride and the respective alcohol in an inert solvent or by alkylation of sodium or triethylammonium salts of acetic acid with primary or secondary alkyl halides, as documented by the procedures for phenyl [ C]acetate 49 , (5)-1,2,2-triphenyl-1,2-ethandiol 2-[ C]acetate 50 and a variety of higher alkyl and aralkyl [ CJacetates 51 °. 

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