Methyltrioctylammonium

Benzyltriethylammonium chloride [56-37-1] is the most widely used catalyst under strongly basic conditions. Methyltrioctylammonium chloride [5137-55-3] (Ahquat 336, Adogen 464) is probably the least expensive catalyst. Others of high activity and moderate price are tetra- -butylammonium chloride [1112-67-0] bromide [1643-19-2] hydrogen sulfate [32503-27-8], tetra- -butylphosphonium chloride [2304-30-5], and other phosphonium salts of a similar number of C atoms. Many other onium salts can also be utilized. 

A mixture of the arylsulfonyl chloride (5 mmol), benzene (2.56 mol), NaN3 (5 mmol), NaHCO, (20 mmol), and methyltrioctylammonium chloride (0.5 mmol), under N2 in an autoclave, was stirred al 40 C for 3 h. The mixture was then heated slowly to 125 C and maintained at this temperature for another 3 h, during which time the pressure in the vessel rose to 31 -54 atm. The mixture was allowed to cool and the autoclave was depressurized. The residual mass was filtered, and the residue washed thoroughly with cold H20. The benzene solution was separated from the aqueous filtrate, dried, and evaporated to give the crude product as a reddish yellow mass which was purified by column chromatography (neutral alumina, hexane/ benzene 3 2). The 1-(arylsulfonyl)-l//-azepines 16 were crystallized from light petroleum ether (bp 60-80 LC). 

Subsequently, cationic rhodium catalysts are also found to be effective for the regio- and stereoselective hydrosilation of alkynes in aqueous media. Recently, Oshima et al. reported a rhodium-catalyzed hydrosilylation of alkynes in an aqueous micellar system. A combination of [RhCl(nbd)]2 and bis-(diphenylphosphi no)propanc (dppp) were shown to be effective for the ( >selective hydrosilation in the presence of sodium dodecylsulfate (SDS), an anionic surfactant, in water.86 An anionic surfactant is essential for this ( )-selective hydrosilation, possibly because anionic micelles are helpful for the formation of a cationic rhodium species via dissociation of the Rh-Cl bond. For example, Triton X-100, a neutral surfactant, gave nonstereoselective hydrosilation whereas methyltrioctylammonium chloride, a cationic surfactant, resulted in none of the hydrosilation products. It was also found that the selectivity can be switched from E to Z in the presence of sodium iodide (Eq. 4.47). 

As we have seen earlier in this chapter, metal catalysts may be made soluble in water by careful design of the ligands around them. Metal catalysed reactions may also be conducted under phase transfer conditions. Here, by contrast, the metal catalyst usually resides in the organic phase and not the aqueous phase. The use of a phase transfer catalyst in these systems may be to transfer a water-soluble metal catalyst into the organic layer, or else to ensure a supply of water-soluble substrate or reagent to a catalyst already resident in the organic phase. An example of the former is the use of methyltrioctylammonium chloride to extract aqueous RhCL... 

More recently, the Noyori group described an organic solvent- and haUde-free oxidation of alcohols with aqueous H202 . The catalyst system typically consists of Na2W04 and methyltrioctylammonium hydrogen sulfate, with a substrate-to-catalyst ratio of 50-500. Secondary alcohols are converted to ketones, whereas primary alcohols, in particular substituted benzyUc ones, are oxidized to aldehydes or carboxylic acid by selecting appropriate reaction conditions This system also catalyzed the chemoselective oxidation of unsaturated alcohols, the transformation exemplified in equation 65, with a marked prevalence for the hydroxy function. 

Since the first uphill (active) transport membrane sensor was proposed in 1986/ this method has already been demonstrated for several liquid membrane systems " by exploiting synthetic molecules, such as methyltrioctylammonium chloride (92 dicyclohexyl-18-crown-6 (93 K" ), and dibenzoyl-... 

Synthesis of aldehydes and ketones.1 The carbanion of 1 can be generated by aqueous NaOH and can be alkylated with use of methyltrioctylammonium chloride as phase-transfer catalyst. A second alkylation is possible using NaH in DMF as base. The dialkylated product (3) can be hydrolyzed to a ketone by HC1 or H2S04 in CH3OH (equation I). 

Azidotrimethylsilane, 24, 217 Diazidodiisopropoxytitanium, 217 Sodium azide-Methyltrioctylammonium chloride, 240 Aziridines... 

Benzyltriethylammonium chloride, 239 Methyltrioctylammonium chloride, 192, 240, 258, 281 Polyethylene glycol, 235 Tetrabutylammonium hydrogensulfate, 94... 

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