Alkyl benzenes under ionic conditions

It is also possible to carry out Friedel-Crafts alkylation in water-stable [bmimjPFe], using the Sc(OTf)3 catalyst for the alkylation of arenes by simple alkenes. In organic solvents, rare earth(ni) salts do not catalyze Friedel-Crafts alkylations, and no reaction is observed under these conditions. However, the reaction of benzene and cyclohexene catalyzed by Sc(OTf)3 in [bmimKSbFe] produces the substituted benzene 67 in a high yield (92%). Since benzene is used as the solvent, the product is isolated by decantation of the organic layer (Scheme 23). No reaction occurs in hydrophilic ionic liquids such as [bmim][BF4] or [bmim][OTf], although... 

It has been reported that t-butyl hypoiodite adds to alkenes via a bridged iodonium ion intermediate in a trans manner in benzene to give P-iodo-ethers in the dark. Unlike the addition in nitrite photolysis, thermal ionic additions may take place in hypoiodite photolysis. The additions in the steroids, even under photolytic conditions, can be rationahzed in terms of an ionic trans-addition of alkyl hypoiodites via bridged iodonium ions, although a homolytic mechanism cannot be excluded. 

A novel ionic liquid methodology for pyrrole C-alkylation is described (Equation 136) <20050L1231>. The pyrrole alkylation is achieved with various simple alkyl halides (1-bromopentadecane, l-(bromomethyl)-, l-(3-chloropropyl)- and l-(3-iodopropyl)benzenes, 2-(2-bromoethyl)- and 2-(3-bromopropyl)naphthalenes) and mesylates (3-phenylpropyl-, l-methyl-3-phenylpropyl-, 2-(2-naphthyl)ethyl- and 3-(2-naphthyl)propyl methanesulfonates) selectively at C(2)- and C(5)-positions in good yields with minimal by-products under relatively mild conditions in various ionic liquids. 2-(3-Phenylpropyl)pyrrole 569 was synthesized from pyrrole and l-bromo-3-phenylpropane in a mixed solvent system, [Bmim][SbF6] and MeCN, in 81% yield at 115°C for 44h with 5% yield of dialkylated compound. 

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