Ionic liquids immobilized catalysts, ester

The same acidic chloroaluminate ionic liquids have been used as solvent for tungsten aryl oxide complexes for the metathesis of alkenes [24]. Slightly acidic chloroaluminates also dissolve the [Cl2W=NPh(PMe3)3] complex which catalyze ethene oligomerization without the addition of co-catalysts [25]. In a similar way, Ni-catalyzed 1-butene dimerization into linear octenes was carried out in acidic chloroaluminates buffered with small amount of weak bases [26]. Neutral chloroaluminates (l-ethyl-3-methylimidazolium chloride/AlCl3 = 1) were employed to immobilize ruthenium carbene complexes for biphasic ADMET (acyclic diene metathesis) polymerization of an acyclic diene ester [27]. 

In these cases, NFSI was preferred to Selectfluor and the reactions were performed either in alcohol or in ionic liquids in which the palladium complexes can be immobilized and reused with excellent reproducibility even after 10 consecutive cycles. For example, the enantioselective electrophilic fluorination of 2-methyl-3-oxo-3-phenylpro-pionic acid tert-butyl ester in [hmim] [BF4] gives the corresponding fluorinated product in 93% yield with 92% ee, and still in 67% yield with 91% ee after 10 cycles. The fluorination of various cyclic and acyclic (3-keto esters was carried out with NFSI in ethanol in the presence of 2.5 mol% of catalyst, leading to excellent ee-values up to 94%. The reaction is not sensitive to water, can be run on a 1-g scale, and proceeds via a palladium enolate complex as for the titanium-4,5-bis(diphenylhydroxymethyl)-2,2-dimethyl-dioxolane (TADDOL) catalyst. The reaction was extended to tert-butoxycarbonyl lactones and lactams. Reactions with lactones proceeded smoothly in an alcoholic solvent with 2.5 mol% of catalyst and NFSI, while the less acidic lactam substrates required concurrent use of the Pd complex and 2,6-lutidine as a co-catalyst. Under the reaction conditions, the fluorinated lactones and lactams were obtained in good yields with excellent enantioselectivities (up to 99%... 

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