Carbonylation, in ionic liquids

It appeared that, we needed to limit or omit the ethyl iodide if we were going to operate the ethylene carbonylation in ionic liquids. Unfortunately, the previous literature indicated that EtI or HI (which are interconvertible) represented a critical catalyst component. Therefore, it was surprising when we found that, in iodide based ionic liquids, the Rh catalyzed carbonylation of ethylene to propionic acid was still operable at acceptable rates in the absence of ethyl iodide, as shown in Table 37.2. Further, we not only achieved acceptable rates when omitting the ethyl iodide, we also achieved the desired reduction in the levels of ethyl propionate. More importantly, when the reaction products were analyzed, there was no detectable ethyl iodide formed in situ. However, we should note that we now observed traces of ethanol which were normally undetectable in the earlier Ed containing experiments. 

Alkoxy)diborons, alkyne additions, 10, 727-728 Alkoxy-hydro carbonylation, in ionic liquids, 1, 863 Alkoxy ketones, asymmetric hydrogenation, 10, 47 Alkoxylation... 

Redel E, Kramer J, Thomaim R, Janiak C (2009) Synthesis of Co, Rh and Ir nanoparticles from metal carbonyls in ionic liquids and their use as biphasic liquid-liquid hydrogenation nanocatalysts for cyclohexene. J Oiganomet Chem 694 1069-1075... 

Vollmer C, Janiak C (2011) Naked metal nanoparticles from metal carbonyls in ionic liquids easy synthesis and stabilization. Coord Chem Rev 255(17-18) 2039-2057. doi 10.1016/j. ccr.2011.03.005... 

In addition to the applications reported in detail above, a number of other transition metal-catalyzed reactions in ionic liquids have been carried out with some success in recent years, illustrating the broad versatility of the methodology. Butadiene telomerization [34], olefin metathesis [110], carbonylation [111], allylic alkylation [112] and substitution [113], and Trost-Tsuji-coupling [114] are other examples of high value for synthetic chemists. 

Unfortunately, when the carbonylation of ethylene with a rhodium-ethyl iodide catalyst was operated in ionic liquid media generated the product mixture now contained a significant amoimt of EtC02Et (15-35%). (See Table 37.1.) Unless this selectivity issue was resolved, the carbonylation of ethylene in ionic liquids would have been imtenable. 

Transition-metal carbonyls, 16 58 Transition metal catalysts, 20 151-152 Transition-metal-catalyzed microwave-assisted reactions, 16 552 Transition metal-catalyzed reactions in ionic liquids, 26 878-897 Transition-metal clusters, structure of,... 

Much less attention has been focused on carbonylation reactions in ionic liquids. The biphasic palladium-catalyzed alkoxy carbonylation of styrene. Scheme 2, in [bmim][BF4]—cyclohexane has been reported. ... 

Guo, S., Shi, R, Gu, Y., Yang, J., Deng, Y., Size-controllable synthesis of gold nanoparticles via carbonylation and reduction of hydrochloroauric acid with CO and H2O in ionic liquids, Chem. Lett., 34,830-831,2005. 

Another interesting carbonylation that has been carried out in ionic liquids is that of 3-alkyn-l-ols and l-alkyn-4-ols by [Pd(OAc)2]/ PyPPh2(PyPPh2=2-(diphenylphosphino)pyridine) to give evo-a-methylene y- and 8-lactones, respectively.60 The products were isolated in almost quantitative yields by distillation under reduced pressure or by solvent extraction from the ionic liquid with diethyl ether. However, when recycling of the ionic liquid solution was attempted for the carbonylation of 3-butyn-l-ol the yield fell from 99 to 37% after only two runs. 

C-H bonds in hydrogenation reactions, 276-277 C-Si bonds, 73 Carbonyl complexes, 184 Carbonyl hafnium complex, 144 Carbonylation of aryl halides, 271-272 Carbonylation reactions in ionic liquids, 271... 

Zulfiqar, F. and Kitazume, T. (2000) Lewis acid-catalysed sequential reaction in ionic liquids. Green Chem., 2, 296-297. Kamal, A. and Chouhan, G. (2004) Investigations towards the chemoselective thioacetalization of carbonyl compounds by using ionic liquid [bmim]Br as a recyclable catalytic medium. Adv. Synth. Catal., 346 (5), 579-582. 

The epoxidation of alkenes, both racemic and enantioselective, has been extensively studied in ionic liquids and Table 5.3 provides a summary of these reactions. Although no transition metal is involved, the base-catalysed epoxidation of electrophilic alkenes in ionic liquids is worth briefly mentioning. Depending on the substrate and the reaction conditions, ,/ -unsaturated carbonyl compounds were oxidised with aqueous H2O2 in [C4Ciim][BF4] or [C4Ciim][PF6] within minutes under mild conditions and no hydrolysis products were observed.120-221 The extraction of the products with scC02 instead of conventional solvents was demonstrated to be feasible, albeit on a small scale.1231... 

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