Rearrangement of phenylethenes on reaction with iodine-xenon difluoride

Article abstract of DOI:10.1021/ol006450d

(matrix presented) Phenyl-substituted ethenes react with iodine and xenon difluoride to provide difluorinated products. Iodofluoro intermediates react with xenon difluoride to produce transient iodine difluoride species that lose IF and F^- and produce carbocations.

Full text of DOI:10.1021/ol006450d

ORGANIC
LETTERS
2000
Vol. 2, No. 21
3359-3360
Rearrangement of Phenylethenes on
Reaction with Iodine−Xenon Difluoride
Timothy B Patrick* and Suntian Qian
Department of Chemistry, Southern Illinois UniVersity, EdwardsVille, Illinois 62026
tpatric@siue.edu
Received August 11, 2000
ABSTRACT
Phenyl-substituted ethenes react with iodine and xenon difluoride to provide difluorinated products. Iodofluoro intermediates react with xenon
difluoride to produce transient iodine difluoride species that lose IF and F- and produce carbocations.
Organic iodine compounds react with xenon difluoride to
produce organoiodine difluorides that undergo transforma-
tions to organofluorine compounds. The reactions occur
through mechanistic paths that involve carbocations.1-10 In
a study of the rearrangements that occur when organoiodine
compounds are treated with xenon difluoride, we found that
alkenes can be treated with iodine and xenon difluoride,
Shellhamer’s reagent,11 to produce intermediate organoiodine
compounds that undergo rearrangement on reaction with the
xenon difluoride as exemplified in Scheme 1.12,13
The mechanistic course of the reaction can be rationalized
as shown in Scheme 2 with triphenylethene (4) as the model
Scheme 2
Scheme 1
In this Letter, we report a continuation of our studies on
the reactions of I2/XeF2 alkenes that contain phenyl substit-
uents.14 The substrates and their reaction products are shown
in Table 1.15
substrate. The alkenes react with iodine fluoride generated
from the reaction between xenon difluoride and iodine in a
(1) Ruppert, I. J. Fluorine Chem. 1980, 15, 173.
(2) Zupan, M. Collect. Czech. Chem. Commun. 1977, 42, 266.
(3) Gibson, J. A.; Janzen, A. F. J. Chem. Soc., Chem. Commun. 1973,
739.
(4) Gibson, J. A.; Marat, R. K.; Janzen, A. F. Can J. Chem. 1975, 53,
3044.
(7) Della, E. W.; Head, N. J. J. Org. Chem. 1992, 57, 2850.
(8) Della, E. W.; Head, N. J.; Janowski, W. K.; Schiesser, C. H. J. Org.
Chem. 1993, 58, 7876.
(5) Alam, K.; Janzen, A. F. J. Fluorine Chem. 1987, 36, 179.
(6) Forster, A. M.; Downs, A. J. Polyhedron 1985, 4, 1625.
(9) Eaton, P. E.; Yang, C.-X.; Xiong, Y. J. Am. Chem. Soc. 1990, 112,
3225.
10.1021/ol006450d CCC: $19.00 © 2000 American Chemical Society
Published on Web 09/19/2000

been postulated in earlier research.12 The intermediate 13
loses IF and F- with rearrangement to produce carbocation
A or without rearrangement to produce carbocation B. The
carbocations react with the fluoride ion to produce the final
products. Carbocation stability likely governs the final
product(s) produced. In all cases where rearrangement is
observed (6, 8, 9), a fluorine-stabilized carbocation inter-
mediate helps to drive the rearrangement.
Table 1
In conclusion, the results show that unusual fluorinated
products can be obtained in moderate to good yields by a
relatively simple process that proceeds by predictable
mechanistic routes.
Acknowledgment. We thank the National Science Foun-
dation (RUI) and the Petroleum Research Fund (Type B)
for support of this research.
OL006450D
(10) Rozen, S.; Brand, M. J. Org. Chem. 1981, 46, 733.
(11) Shellhamer, D. L.; Jones, B. C.; Pettus, B. J.; Pettus, J. M.; Stringer,
J. M.; Heasley, V. L. J. Fluorine Chem. 1998, 88, 37.
(12) Patrick, T. B.; Zhang, L. Tetrahedron Lett. 1997, 38, 8925.
(13) Patrick, T. B.; Zhang, L.; Li, Q. J. Fluorine Chem. 2000, 102, 11.
(14) Iodine (0.3 mmol) is added to the alkene (0.3 mmol) in 2 mL of
CDCl3 at room temperature. XeF2 (0.61 mmol) is added, and the mixture
is stirred overnight. The purple reaction mixture is subjected to column
chromatography on silica gel with hexanes-ethyl acetate eluent.
(15) All compounds were characterized by NMR and high-resolution
MS analysis. Representative NMR data follow. Compound 6: 1H (TMS) δ
3.15 (CH2, t of d, JHF ) 17.4 Hz, JHH ) 4.5 Hz), 5.85 (CH, t of t, JHF
)
57 Hz, JHH ) 4.5 Hz), 7-7.6 (aromatic); 19F (TFA) -39.2 (m); MS calcd
142.0594 amu, obsd 142.0580. Compound 7: 1H δ 5.7 (CH, partial d of
d), 6.6-7.8 (aromatic); 19F -109 (m), -110.4 (m); 13C δ 94 (d of d), 96
(d of d), 127-132 (aromatic); MS calcd 220.1064, obsd 220.1069.
Compound 8: 1H δ 3.36 (t,CH2, J ) 18 Hz), 6.9-7.6 (aromatic); 19F -19.2
(t,CF2, J ) 18 Hz); 13C 45.9 (t, CH2, JCF ) 11 Hz), 121.9 (t, CF2, JCF
)
240 Hz), 130-140 (aromatic); MS calcd 220.1064, obsd 220.1051.
Compound 9: 1H δ 4.61 (t, CH, JHF ) 16.9 Hz), 7-7.8 (aromatic); 19F
-20.9 (d, CF2, JHF ) 16.9 Hz); 13C 59 (t, CH, JCF ) 13 Hz), 130-140
(aromatic); MS calcd 294.1221, obsd 294.1200. Compound 10: 1H δ 6.2
(dd, CH, JHFgem ) 30 Hz, JHFvic ) 9 Hz), 7.8 (aromatic), 19F -83.7 (m,
CF), -105.4 (d of m, CHF); 13C 98.1 (dd, CHF, JCF gem ) 216 Hz, JCF vic
regioselective process that places the fluorine atom at the
site of the more stable carbocation to produce the intermedi-
ate iodofluorinated intermediate 12. Intermediate 12 reacts
with a second equivalent of xenon difluoride to produce the
iodine difluoride intermediate 13. Similar intermediates have
) 21 Hz), 106.1 (dd, CF, JCF
) 142 Hz, JCF
) 21 Hz), 120-130
vic
gem
(aromatic); MS calcd 294.1221, obsd 294.1249. Compound 11: 1H δ 6.9-
7.4 (aromatic); 19F -73.0 (s, CF); 13C 99.0 (d,d CF, JCFgem ) 190 Hz, JCFvic
) 30.4; MS calcd 349.9997, obsd 349.9984.
3360
Org. Lett., Vol. 2, No. 21, 2000