Ammonium salt catalyst

Synthesis of dimethyl carbonate by transesterification of ethylene carbonate and methanol using quaternary ammonium salt catalysts... 

Quaternary ammonium salt catalysts based on diff mt alkyl cations such as tetrapropylammonium (TPA, tetrabutylammonium (TBA, tetrahex5dammonium (THA ), tetraoctylammonium (TOA, tetradodecylammonium (TDodA, and those with different anions such as Q, Bf, and f were used. 

The synthesis of DMC from EC and methanol was carried out in a batch reactor using various quaternary ammonium salt catalysts under carbon dioxide pressure. 

In the synthesis of DMC fiom the transesterification of EC and methanol, quaternary ammonium salt catalysts showed good catalytic activity. The main byproduct was ethylene glycol. The quaternary salt with the cation of bulkier alkyl chain laigth and witii more nucleophilic anion showed better reactivity. Hi temperature and large amount of catalyst increased the conversion of EC. The EC conversion and DMC selectivity increased as the pressure of CO2 increased from 250 to 350 psig. 

Another substituted derivative of BINAP was used by Lemaire et al. [109]. The ammonium salt catalysts (7 and 8, Fig. 41.10) were prepared in situ from the bro-mohydrates and [Ru( /3-2-methylallyl)2(/72-COD)], and immobilized in several ionic liquids. By comparative studies of the hydrogenation of ethyl acetoacetate, the best results were obtained with imidazolium- and pyridinium-containing ionic liquids. No significant ee was observed with the phosphonium salt. This observation was attributed to problems of solubility and to the ability of complexation for the phosphonium ion. From the anionic side, use of the [BF4] anion appeared superior compared to [PF6] and [(CF3S02)2N]A... 

A combined -cyclodextrin quatemary ammonium salt catalyst promotes the addition of the trichloromethyl anion to aromatic aldehydes and enhances the yield of the a-hydroxy acid [7],... 

The combination of Me2AlCN and BINOL (1.2 equiv.) also induced the cyanation of imines derived from benzaldehyde, affording the Strecker products in up to 70% ee [76]. Finally, N-allylbenzaldimines have been reported to react with HCN in the presence of chiral ammonium salt catalysts [77, 78]. 

The synthesis of 5-membered cyclic carbonates is carried out by the reaction of oxirane with carbon dioxide in the presence of various quartemary ammonium salts catalyst as shown in Scheme 1 and their results are listed in Table 1. 

Carbon dioxide can effectively be added to the epoxide ring of GVE to produce the corresponding cyclic carbonate, OVE. Quaternary ammonium salt catalysts showed good catalytic activity even at atmospheric pressure of carbon dioxide. Since the blends of poly(OVE-co-AN) and SAN showed good miscibility, catalytic fixation of carbon dioxide to polymer blends via cyclic carbonate could be one of choice for the reduction and utilization of the greenhouse gcis. 

Alkylation of phthalimide anion can be carried out under solid-liquid phase-transfer conditions, using phosphonium salts or ammonium salts. In the reaction systems using hexadecyltributylphosphonium bromide, alkyl bromides and alkyl methanesulfonate are more reactive than alkyl chlorides. Octyl iodide is less reactive than the corresponding bromide and chloride. ( )-2-Octyl methanesulfonate was converted into (S)-2-octylamine with 92.5% inversion. Kinetic resolution of racemic ethyl 2-bromopro-pionate by the use of a chiral quaternary ammonium salt catalyst has been reported. Under liquid-liquid phase-transfer conditions, A -alkylation of phthalimide has been reported to give poor results. ... 

A number of developmental methodologies which are of interest in the herbicidal field have been examined for the formation of carbamates and related intermediates. Phosgene and phenol reacted in the presence of triphenylphosphine and a quaternary ammonium salt catalyst at 120-125°C over a total period of 10 hours gave phenyl chloroformate in 89% yield (ref.26). 

Yang and Wu [201] investigated the esterification of dipotassium phthalate with benzyl bromide in a solid-liquid system. We found that the catalytic intermediate, formed by the solid reactant with tetrabutylammonium bromide, was the key-reacting component in SLPTC. Yang and Wu [202] explored the kinetics of the O-allylation of sodium phen-oxide with allyl bromide in the presence of quaternary ammonium salt catalyst in a solid-liquid system. The behaviors of the catalytic intermediate tetrabutylammonium phenox-ide, formed from the reaction of solid sodium phenoxide and tetrabutylammonium bromide in the solid-liquid phases, are important in conducting the etherification, and pseudo-first-order kinetics are observed. 

Production is carried out by liquid-phase synthesis from acetaldehyde and ammonia. Acetaldehyde is first trimerized to paraldehyde. The subsequent reaction with aqueous ammonia, which gives a 70% yield of 5-ethyl-2-methylpyridine, is performed in the liquid phase at 230 °C and at a pressure of around 150 bar with ammonium-salt catalysts. 

An enantioselective inter-molecular oxidative dehydrogenative a-alkylation of aldehydes, via benzylic C—H bond activation in MeN02 using molecular O2 as the oxidant and (135) as an organocatalyst, was exemplified by the reaction of 9//-xanthene with hexanal. The ammonium salt catalysts played dual roles not only as enamine catalysts but also as acid catalysts and the desired product was obtained in 81% yields with 73% i... 

There has been interest in employing chiral catalysts in phase-transfer reactions in order to achieve absolute asymmetric synthesis. Chirality may be contained in the carbon skeleton, or the nitrogen of the quaternary ammonium salt catalyst, or in a combination of these. However, unless the nucleophilic or basic anion forms a very tight ion pair with the ammonium cation so that it is associated on only one face of the tetrahedron, simple chiral tetralkylammonium salts will be incapable of producing a significant amount of asymmetric induction. ... 

In the range of the study of new processes to improve the atom efficiency, the discovering versatility of a catalyst as multifunctional catalyst in a transformation is important. On the strength of this concept. Jiao and coworkers reported an enantioselective reduction and alkylation reaction of a,p-unsaturated aldehydes with alcohols, in which the ammonium salt catalyst performed three kinds of catalytic functions, namely, iminium catalysis, enamine catalysis, and acid catalysis [90]. 

S. K. Xiang, B. Zhang, L. H. Zhang, Y. Cui, N. Jiao, Chem. Commun. 2011, 47, 5007-5009. The versatile roles of ammonium salt catalysts in enantioselective reduction and alkylation of a, 3-unsaturated aldehydes iminium catalysis, enamine catalysis and acid catalysis. 

Amer L, Qrshav V., Blum J. Disproportionation and dehydrogenation of 1,3-cyclohexadienes in the presence of recyclable RhCls-quaternary ammonium salt catalysts. J. Mol. Catal. 1988 45 207-214... 

Blum J. The versatility of metal halide-quaternary ammonium salt catalysts for organic processes. From homogeneous to glass-encapsulated ion pairs. Russ. Chem. Bull. 1993 42 1619-1627... 

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