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Ionic liquids in Barbier-Zaitsev reaction. Synthesis of 1-(perfluorophenyl)-2-phenylethanol in the presence of iron pentacarbonyl

“…These reactions are possible only at the use of metallocomplex initiators [2], for instance, the radical addition to the double C=C bond and the telomerization involving the benzyl bromide proceed under the action of the iron pentacarbonyl only in the presence of nucleophilic additive [3]. We have demonstrated that Fe(CO) 5 is an efficient promotor of the alkyl halides addition to the double bonds [1,3] C=C and C=O, and also of nitriles and esters of halogen-substituted acids to benzaldehydes and perfluorinated ketones by the type of reactions of Reformatsky [4] and Barbier-Zaitsev [5,6]. However benzyl bromide is an exception from this series for its addition to aromatic aldehydes initiated by Fe(CO) 5 along the Barbier-Zaitsev reaction becomes possible only in the presence of nucleophilic additives (HMPA, DMF) [6], and in both cases alongside the addition product forms dibenzyl as a side product.…”

“…In this study we for the first time performed the addition of benzyl bromide (I) to pentafluorobenzaldehyde (II) to obtain 1-(perfluorophenyl)-2-phenylethanol (III) by Barbier-Zaitsev reaction (see the scheme) promoted with Fe(CO) 5 in the presence of molar amount of IL.…”

“…According to the published data the ionic liquids decompose in the presence of strong nucleophiles [10] as probably occurs also in our case. The yields of 1-(perfluorophenyl)-2-phenylethanol obtained in the reaction of benzyl bromide (II) with pentafluorobenzaldehyde (I) in the presence of Fe(CO) 5 and ionic liquids IV-VII are given in the table.…”

“…We studied the reaction at various reagents ratios and temperatures (see the table); however the reaction did not occur without Fe(CO) 5 . The established optimum conditions of the reaction are as follows: equimolar amounts of IL V and reagents I and II, double excess of Fe(CO) 5 , 60°C.…”

“…The low yield of the product in the reaction in the presence of IL IV evidently are due to the fast and irreversible decomposition of Fe(CO) 5 in the presence of chloride anion.…”