Synthesis and reactivity of fluorous and nonfluorous aryl and alkyl iodine(III) dichlorides: new chlorinating reagents that are easily recycled using biphasic protocols.
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abstract
Fluorous aryl and alkyl iodine(III) dichlorides of the formulas (R(fn)(CH(2))(3))(2)C(6)H(3)ICl(2) (R(fn) = CF(3)(CF(2))(n-1); n = 8 for 3,5-disubstituted and n = 6, 8, 10 for 2,4-disubstituted) and R(fn)CH(2)ICl(2) (n = 8, 10) are prepared in 71-98% yields by reactions of Cl(2) and the corresponding fluorous iodides. These are effective reagents for the conversions of cyclooctene to trans-1,2-dichlorocyclooctene, anisole to 4-chloro- and 2-chloroanisole, 4-tert-butylphenol to 2-chloro-4-tert-butylphenol, PhCOCH(2)COPh to PhCOCHClCOPh, and PhCOCH(3) to PhCOCH(2)Cl and PhCOCHCl(2) (CH(3)CN, rt to 40 degrees C, 100-64% conversions). The chlorinated products and fluorous iodide coproducts are easily separated by organic/fluorous liquid/liquid biphase workups. The latter are obtained in 97-90% yields and reoxidized with Cl(2). Analogous chlorinations are conducted with 3-Cl(2)IC(6)H(4)COOH (16) and 4,4'-Cl(2)IC(6)H(4)C(6)H(4)ICl(2). With the former, the products and coproduct 3-IC(6)H(4)COOH (91-85% recoveries) are easily separated by organic/aqueous NaHCO(3) liquid/liquid biphase workups. The coproduct from the latter, 4,4'-IC(6)H(4)C(6)H(4)I, is insoluble in common organic solvents, allowing separation by liquid/solid phase workups (91-89% recoveries). The effect of the structure of the iodine(III) dichloride upon reactivity is analyzed in detail. The fluorous systems with R(f8) substituents are generally superior, but 16 is more reactive and gives higher selectivities.
