Convenient syntheses of fluorous aryl iodides and hypervalent iodine compounds: ArI(L)(n) reagents that are recoverable by simple liquid/liquid biphase workups, and applications in oxidations of hydroquinones

摘要

Iodinations of the ortho, meta, and para fluorous arenes (Rf8CH2-CH2CH2)(2)C6H4 (R-f8 = (CF2)(7)CF3) with I-2/H5IO6 in AcOH/H2SO4/H2O give 3,4(Rf8CH2CH2CH2)(2)C6H3I (5) and the analogous 2,4- (6) and 2,5- (7) isomers, respectively. Spectroscopic yields are > 90 %, but 5 and 7 must be separated by chromatography from by-products (yields isolated: 70 %, 97 %, 61 %). Reaction of 1,3,5-(Rf8CH2CH2CH2)(3)C6H3 with PhI(OAc)(2)/I-2 gives 2,4,6(Rf8CH2CH2CH2)(3)C6H2I (8) on multigram scales in 97 % yield. The CF3C6F11/toluene partition coefficients of 5-8 (24degreesC: 69.5:30.5 (5), 74.7:25.3 (6), 73.9:26.1 (7), 98.0:2.0 (8)) are lower than those of the precursors, but CF3C6F11/MeOH gives higher values (97,03.0 (5), 98.6:1.4 (6), 98.0:2.0 (7), > 99.3: < 0.3 (8)). Reactions of 5-8 with excess NaBO3 in AcOH yield the corresponding ArI(OAc)(2) species 9-12 (9, 85 % as a 90:10 9/5 mixture; 10, 97 %; 11, 95 %; 12, 93 % as a 95:5 12/8 mixture). These rapidly oxidize 1,4-hydroquinones in MeOH. Subsequent additions of CF3C6F11 give liquid biphase systems. Solvent removal from the CF3C6F11 phases gives 5-8 in > 99-98% yields, and solvent removal from the MeOH phases gives the quinone products, normally in > 99-95% yields. The recovered compounds 5-8 are easily reoxidized to 9-12 and used again. [References: 77]