Abstraction of Iodine by Alkyl Radicals
was transferred to a distillation apparatus together with 100 mL of
water and distilled. The distillate was extracted with petroleum ether,
the organic layer was dried with anhydrous sodium sulfate, the
solvent was evaporated under reduced pressure, and 2.37 g of the
yellow oil was obtained. A part (1.10 g) of the above oil was
chromatographed (silica, CH2Cl2/petroleum ether 1:1) and 633 mg
(29%) of pure 13b was isolated as a colorless oil. 1H NMR (CDCl3)
δ/ppm 1.04 (q, 5JF-H ) 1.2 Hz, 9H), 2.5 (br s, 1H), 7.36 (m, 3H),
Recystallization from hexane yielded 246 mg (29%) of colorless
crystals, mp 32-33.5 °C. 1H NMR (CDCl3) δ/ppm 3.54 (septet, J
) 1.1 Hz, 3H), 7.08 (ddd, J ) 1.6, 7.3, 8.0 Hz, 1H), 7.43 (ddd, J
) 1.4, 7.3, 8.1 Hz, 1H), 7.55 (br d, J ) 8.1 Hz, 1H), 8.19 (dd, J
) 1.4, 8.0 Hz, 1H). 13C NMR (CDCl3) δ/ppm 54.9 (CH3), 84.1
(septet, JF-C ) 28.1 Hz, C), 92.4 (C), 122.5 (q, JF-C ) 292.6
Hz, CF3), 128.0 (CH), 129.1 (C), 131.3 (CH), 131.5 (CH), 145.2
(CH). MS, EI, m/z (%) 384 (M+, 80), 315 (100), 231 (34), 207
(16), 157 (17), 145 (17), 127 (39), 123 (85), 107 (11), 91 (16), 69
(22). Anal. Calcd for C10H7F6IO: C, 31.27; H, 1.81. Found: C,
31.14; H, 1.85.
2
1
4
7.58 (m, 2H). 13C NMR (CDCl3) δ/ppm 26.3 (q, JF-C ) 2.2 Hz,
2
1
CH3), 37.9 (C), 81.8 (q, JF-C ) 25.8 Hz, C), 126,92 (q, JF-C
)
289.1 Hz, CF3), 126,93 (CH), 127.5 (CH), 128.0 (CH), 137.1 (C).
19F NMR (CDCl3) δ/ppm -68.6 (s). MS, EI, m/z (%) 232 (M+, 1),
175 (6), 105 (21), 77 (12), 57 (100). Anal. Calcd for C12H15F3O:
C, 62.06; H, 6.51 Found: C, 61.76; H, 6.41.
1,1,1,3,3,3-Hexafluoro-2-(2-iodo-5-methylphenyl)-2-meth-
oxypropane (15a). Sodium hydride (80% suspension in mineral
oil, 67 mg, 2.2 mmol) was washed with pentane and dry diethyl
ether in a V vial and diluted with 1 mL of dry ether. After cooling
in an ice bath, 384 mg of alcohol 5a was added, followed by 0.7
mL (11 mmol) of iodomethane. The vial was capped and stirred
for 5 days at approximately 35 °C. The reaction mixture was diluted
with ether, washed twice with water, and dried with anhydrous
sodium sulfate, and the solvent was evaporated under reduced
pressure. The white, crystalline product (360 mg, 90%) was
recrystallized from methanol and 223 mg (56%) of white needles
1-Chloro-3-(1,1-dimethylethyl)-3-trifluoromethyl-1H-benzo-
iodoxole (13c). TMEDA (0.31 g, 2.5 mmol) and 5 mL of 1.6 M
butyllithium solution in hexane were placed in a three-necked flask
under argon, and the mixture was stirred for 30 min. To this was
added 620 mg of 13b in 1 mL of pentane, and the resulting mixture
was stirred for 20 h at room temperature, then cooled in an ice
bath, and 2.0 g (8 mmol) of solid iodine was added. After 10 min,
the mixture was diluted with diethyl ether, washed with aqueous
sodium sulfite, citric acid, and water, and dried with anhydrous
sodium sulfate, and after evaporation of solvent, 607 mg of a brown
oil was obtained. The crude product was chromatographed on silica
(CH2Cl2/petroleum ether 1:1.5), and 155 mg of impure iodo alcohol
was isolated. This product was dissolved in 0.5 mL of hexane and
treated with 110 mg (1 mmol) of tert-butyl hypochlorite at room
temperature. Upon cooling, 95 mg (9%) of 13c as a yellow
precipitate was filtered off: mp 94-122 °C.45 1H NMR (CDCl3)
1
(mp 72.5-73.5 °C) were isolated. H NMR (CDCl3) δ/ppm 2.34
(s, 3H), 3.53 (m, 3H), 6.91 (dd, J ) 1.7, 8.1 Hz, 1H), 7.32 (br s,
1H), 8.04 (d, 8.1 Hz, 1H). 13C NMR (CDCl3) δ/ppm 21.1 (CH3),
2
54.9 (CH3), 84.1 (septet, JF-C ) 28.1 Hz, C), 88.3 (C), 122.5 (q,
1JF-C ) 292.1 Hz, CF3), 128.8 (C), 132.2 (m, CH), 132.3 (CH),
138.2 (C), 144.8 (CH). 19F NMR (CDCl3) δ/ppm -68.6 (s). MS,
EI, m/z (%) 398 (M+, 90), 329 (100), 245 (45), 151 (31), 137 (93),
127 (11), 90 (22), 69 (16), 63 (17). Anal. Calcd for C11H9F6IO: C,
33.19; H, 2.28. Found: C, 33.01; H, 2.24.
5
δ/ppm 1.11 (q, JF-H ) 1.1 Hz, 9H), 7.61 (m, 2H), 7.71 (m, 1H),
8.07 (d, J ) 8.4 Hz, 1H). 13C NMR (CDCl3) δ/ppm 26.5 (q, 4JF-C
) 1.8 Hz, CH3), 41.6 (q, 3JF-C ) 1.0 Hz, C), 91.0 (q, 2JF-C ) 26.8
Hz, C), 114.4 (C), 126,4 (q, 1JF-C ) 289.9 Hz, CF3), 128.3 (CH),
Computations. All HF and DFT calculations were carried out
on Gaussian 0347 except for the transition state Ph-I-Me, which
were carried out on Jaguar 6.5, Schrodinger, LLC, New York, 2005.
Initial optimizations on semiempirical level were made by Hyper-
Chem (Hypercube Inc., release 6.0) package. Energies of formation
and zero-point vibrational energies were calculated on fully
optimized structures by use of B3LYP/6-31G(d,p) and Lanl2mb
basis sets for iodine. Transition states were optimized by standard
methods at the B3LYP/6-31G(d,p) (Gaussian) or MPW1K/
LACV3P** (Jaguar) level of theory.
Kinetic Measurements. In a typical experiment, a reaction
mixture made up of substituted iodobenzene (15 mM), tetrachlo-
romethane (50 mM), bromobenzene (internal standard, 20 mM),
and DBPO (1 mM) in argon-purged cyclohexane was filled under
argon atmosphere into glass ampules (three for each point) and
sealed (the amounts of tetrachloromethane and the initiator were
varied, depending on the reactivity of substrate). Ampules were
heated in a water bath thermostat at various temperatures (35-71
°C) for at least 10 half-lives of the initiator at that temperature.
The amounts of iodocyclohexane and chlorocyclohexane formed
were then measured by GC. Relative rates k(1)/k(Cl) were calculated
by using the integrated rate equation k(1)/k(Cl) ) ln [(A - X)/A]/
129.7 (q, J ) 2.5 Hz, CH), 130.3 (CH), 132.0 (CH), 139.1 (C). 19
F
NMR (CDCl3) δ/ppm -70.63 (s). MS, EI, m/z (%) 395 (M+ + 3,
0.1), 393 (M+ + 1, 0.3), 357 (2), 335 (34), 300 (65), 231 (100),
203 (45), 127 (6), 123 (20), 76 (46), 69 (10), 57 (97). Anal. Calcd
for C12H13ClF3IO: C, 36.71; H, 3.34 Found: C, 36.80; H, 3.58.
1,1,1-Trifluoro-3,3-dimethyl-2-(2-iodophenyl)butan-2-ol (13).
Compound 13c (80 mg, 0.20 mmol) was dissolved in 1 mL of
methanol, and a solution of 25 mg (11 mmol) of K2S2O5 in 0.5
mL of water was added under stirring at room temperature. After
20 min, the mixture was diluted with diethyl ether and water, the
organic layer was washed with water and dried, and after evap-
oration of the solvent, 63 mg (86%, 2.2% overall) of 13 as a
colorless oil was obtained. 1H NMR (CDCl3) δ/ppm 1.13 (q, 5JF-H
) 1.1 Hz, 9H), 2.8 (br s, 1H), 6.95 (ddd, J ) 1.5, 7.2, 7.9 Hz, 1H),
7.33 (ddd, J ) 1.5, 7.2, 8.5 Hz, 1H), 7.50 (m, 1H), 8.10 (dd,
4
J ) 1.5, 8.0 Hz, 1H). 13C NMR (CDCl3) δ/ppm 26.8 (q, JF-C
)
2
2.3 Hz, CH3), 40.2 (C), 83.2 (q, JF-C ) 25.3 Hz, C), 91.5 (C),
126.6 (q, 1JF-C ) 290.6 Hz, CF3), 126.6 (CH), 129.5 (CH), 130.2
(q, J ) 4.4 Hz, CH) 136.0 (C), 144.7 (CH). 19F NMR (CDCl3)
δ/ppm -67.07 (s). MS, EI, m/z (%) 358 (M+, 0.5), 302 (6), 231
(15), 203 (4), 127 (2), 105 (8), 77 (10), 57 (100). Anal. Calcd for
C12H14F3IO: C, 40.24; H, 3.94 Found: C, 40.37; H, 4.07.
(47) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin, K.
N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.;
Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.;
Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.;
Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li,
X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Adamo, C.; Jaramillo, J.;
Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.;
Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.; Voth, G. A.;
Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels,
A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.;
Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.;
Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz,
P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.;
Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson,
B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian 03,
Revision B.03; Gaussian, Inc.: Pittsburgh, PA, 2003.
1,1,1,3,3,3-Hexafluoro-2-(2-iodophenyl)-2-methoxypropane
(14a). Sodium hydride (0,11 g, 3.9 mmol, 85% dispersion in mineral
oil) was placed in a V vial and washed with pentane and anhydrous
diethyl ether. Hydride was diluted with 1 mL of dry THF, and 810
mg (2.2 mmol) of 14 was slowly added under stirring. After the
evolution of gas ceased, 1.0 mL of methyl iodide was added, and
the vial was capped and placed into a sand bath with a temperature
of approximately 50 °C. After 2 days (when GC showed complete
conversion of the starting alcohol), the reaction mixture was diluted
with diethyl ether and washed with aqueous citric acid and water,
and the organic layer was dried with anhydrous sodium sulfate.
After evaporation of the solvent under reduced pressure, 318 mg
(38%) of colorless oil remained, which crystallized in a refrigerator.
J. Org. Chem, Vol. 71, No. 21, 2006 8035