Phase transfer catalysts, laboratory

The refined grade s fastest growing use is as a commercial extraction solvent and reaction medium. Other uses are as a solvent for radical-free copolymerization of maleic anhydride and an alkyl vinyl ether, and as a solvent for the polymerization of butadiene and isoprene usiag lithium alkyls as catalyst. Other laboratory appHcations include use as a solvent for Grignard reagents, and also for phase-transfer catalysts. 

The feasibility of reusing the phase transfer catalyst via the reuse of the third liquid phase in a tri-liquid catalytic system has been investigated in our laboratory [6,7]. In the present study, the catalyst-rich liquid phase was repeatedly used for four times and the changes in the conversion of RBr and the fractional yield of ROAc were observed. 

Phase transfer catalytic processes (1-3) have been the subject of intensive study in many laboratories throughout the world since its potential was recognized almost simultaneously and independently by Starks ( ) and Makosza (. The principles outlined by Starks in 1971 ( ) have generally stood the test of time even though many compounds besides quaternary oniurn salts have been utilized as phase transfer catalysts (1-3). 

Several families of efficient chiral phase transfer catalysts are now available for use in asymmetric synthesis. To date, the highest enantiomeric excesses (>95% ee) are obtained using salts derived from cinchona alkaloids with a 9-anthracenylmethyl substituent on the bridgehead nitrogen (e.g. lb, 2b). These catalysts will be used to improve the enantiose-lectivity of existing asymmetric PTC reactions and will be exploited in other anion-mediated processes both in the laboratory and industrially. 

The first experiments which were carried out in the author s laboratory on organometallic phase-transfer catalysis were concerned with the reduction of nitrobenzenes (4) to anilines (5) by triiron dodecacarbonyl. Such a conversion was reported to occur in benzene containing methanol at reflux for 10-17 h, with the hydridoundecacarbonyltriferrate anion as the likely key intermediate (16). It was our expectation that the trinuclear iron hydride should be generated by phase-transfer catalysis and if so, effect reduction of nitro compounds (4) under exceedingly mild conditions. Indeed this was the case, as illustrated by the results shown in Table I (17). Not only is the reaction complete in 2 h or less using sodium hydroxide as the aqueous phase, benzene as the organic phase, and benzyltrieth-ylammonium chloride as the phase-transfer catalyst, but it occurs at room temperature and requires less metal carbonyl than when the reaction was... 

Uses Surfactant detergent laboratory reagent phase transfer catalyst antistat for textile spin finishes germicide preservative in cosmetics antistat conditioner skin disinfectant pharmaceuticals (topical antiseptic, preservative)... 

One of the most important metal carbonyl anions, as far as catalytic processes are concerned, is the cobalt tetracarbonyl anion, Co(CO)4. Prior to attempting phase-transfer catalysis using Co(CO)4" as a catalyst, it was imperative to establish that the anion is actually formed under these conditions. Therefore, model experiments in the author s laboratory involved the initial use of dicobalt octacarbonyl in a stoichiometric role. 

SoHd-liguid phase-transfer catalysis. Crown ethers have commonly been used as catalysts for reactions between a solid-liquid interface, and quaternary ammonium and phosphonium salts have been used only as catalysts for reactions in two-phase liquid liquid reactions. However, several laboratories have reported that the latter catalysts are also satisfactory for two-phase solid liquid reactions. Thus dichlorocarbene can be generated from chloroform and solid sodium hydroxide under catalysis from benzyltriethylammonium chloride in yields comparable to those of the classical Makosza method. Another example of this type of catalysis is the oxidation of terminal and internal alkynes by solid potassium permanganate in CH2CI2 with Adogen 464 as catalyst. Aliquat 336 has been found to be as satisfactory as a crown ether for certain displacement reactions with NaOAc, KSCN, KNOa, and KF in CH3CN or CHaCla. ... 

Applications for OSN have been under pilot-plant trial or demonstrated in laboratory experiments in solvent deoiling, homogeneous catalyst recovery, separation of phase-transfer agents, and solvent exchange. "... 

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