LETTER
Pentafluorophenyl End-Capped Polyynes
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(2) Smith, C. E.; Smith, P. S.; Thomas, R. L.; Robins, E. G.;
Collings, J. C.; Dai, C.; Scott, A. J.; Borwick, S.; Batsanov,
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organization was somewhat different to that found for
pure 5. In this case, two crystallographically independent
molecules of 5 pack in the unit cell: molecules A and B
(Figure 5a). Each forms a centrosymmetric dimeric pair
with its nearest neighbor separated by 3.43 Å (A–A pair)
and 3.46 Å (B–B pair).27 Likewise, neighboring A–B
pairs are packed at an analogous distance of 3.46 Å.
Whereas pure 5 shows a lateral offset of neighboring mol-
ecules, the inclusion of decafluorotolan gives rise to an al-
ternating pattern of molecules A–A–B (Figure 5b), with
center-to-center distances of d = 3.76 Å (A–A) and 3.65 Å
(A–B). The next series of three molecules is then offset,
with d = 3.72 (B–B). Thus, the same overall relative pack-
ing is observed with respect to pure 5, but with a slightly
different lateral arrangement. Finally, the incorporation of
the decafluorotolan can be best appreciated as viewed
down the crystallographic c axis, which shows each
‘guest’ molecule sandwiched between ca. four molecules
of 5 in neighboring tiers of the structure.
(7) Kendall, J.; McDonald, R.; Ferguson, M. J.; Tykwinski,
R. R. Org. Lett. 2008, 10, 2163.
(8) For examples based on acetylenic derivatives, see: (a) Shu,
L.; Müri, M.; Krupke, R.; Mayor, M. Org. Biomol. Chem.
2009, 7, 1081. (b) Tahara, K.; Fujita, T.; Sonoda, M.; Shiro,
M.; Tobe, Y. J. Am. Chem. Soc. 2008, 130, 14339.
(c) Armitt, D. J.; Bruce, M. I.; Gaudio, M.; Zaitseva, N. N.;
Skelton, B. W.; White, A. H.; Le Guennic, B.; Halet, J.-F.;
Fox, M. A.; Roberts, R. L.; Hartl, F.; Low, P. J. Dalton
Trans. 2008, 6763. (d) Mu, Z.; Shu, L.; Fuchs, H.; Mayor,
M.; Chi, L. J. Am. Chem. Soc. 2008, 130, 10840.
In summary, several synthetic routes toward pentafluo-
rophenyl polyynes have been explored and developed.32
In the course of this investigation, it has become clear that
the presence of pentafluorophenyl groups can present
unique synthetic challenges. Transformations that have
historically worked well with other substitution patterns
can fail in the presence of the pentafluorophenyl moiety,
often without an obvious explanation. Furthermore, the
presence of the C6H5 group does not generally complicate
the FBW rearrangement; i.e., no substantial addition of n-
BuLi to the C6H5 group is observed and the reaction rate
for the rearrangement in the presence of this group is not
altered to any great extent.
(e) Taylor, T. J.; Gabbai, F. P. Organometallics 2006, 25,
2143. (f) Xu, R.; Gramlich, V.; Frauenrath, H. J. Am. Chem.
Soc. 2006, 128, 5541. (g) Shu, L.; Mu, Z.; Fuchs, H.; Chi,
L.; Mayor, M. Chem. Commun. 2006, 1862. (h) Collings,
J. C.; Burke, J. M.; Smith, P. S.; Batsanov, A. S.; Howard,
J. A. K.; Marder, T. B. Org. Biomol. Chem. 2004, 2, 3172.
(i) Watt, S. W.; Dai, C.; Scott, A. J.; Burke, J. M.; Thomas,
R. L.; Collings, J. C.; Viney, C.; Clegg, W.; Marder, T. B.
Angew. Chem. Int. Ed. 2004, 43, 3061. (j) Gdaniec, M.;
Jankowski, W.; Milewska, M. J.; Polonski, T. Angew. Chem.
Int. Ed. 2003, 42, 3903. (k) Johnson, S. A.; Liu, F.-Q.; Suh,
M. C.; Zürcher, S.; Haufe, M.; Mao, S. S. H.; Tilley, T. D.
J. Am. Chem. Soc. 2003, 125, 4199.
Solid-state structural analysis of a number of systems re-
veals that the interactions between pentafluorophenyl and
phenyl polyynes offer a powerful mode of supramolecular
organization, including the formation of inclusion com-
plexes. Our study of these molecules continues.
(9) Kaafarani, B. R.; Wex, B.; Strehmel, B.; Neckers, D. C.
Photochem. Photobiol. Sci. 2002, 1, 942.
(10) Data for 1 (C8HBr2F5), Fw = 351.91; monoclinic crystal
system; space group P21/n (an alternate setting of P21/c [No.
14]), a = 4.2574(6), b = 37.836(5), c = 5.8166(8) Å;
b = 96.478(2)°; V = 931.0(2) Å3; Z = 4; rcalcd = 2.511 g
cm–3; 2qmax = 52.68°; m = 8.744 mm–1; T = –80 °C; total data
collected = 7332; R1 = 0.0688 [1617 observed reflections
Acknowledgment
This work has been generously supported by the University of Al-
berta and the Natural Sciences and Engineering Research Council
of Canada (NSERC) through the Discovery Grant program.
2
with Fo2 ≥ 2s(Fo )]; wR2 = 0.1884 for 136 variables and
2
1900 unique reflections with Fo2 ≥ –3s(Fo ); residual
electron density = 1.576 and –1.452 e Å–3. CCDC 725485.
(11) Barrow, I.; Pedler, A. E. Tetrahedron 1976, 32, 1829.
(12) (a) Waugh, F.; Walton, D. R. M. J. Organomet. Chem. 1972,
39, 275. (b) Zhang, Y.; Wen, J. Synthesis 1990, 727.
(13) Hay, A. S. J. Org. Chem. 1962, 27, 3320.
References and Notes
(1) (a) Chalifoux, W. A.; Tykwinski, R. R. C. R. Chim. 2009, 12,
341. (b) Shi Shun, A. L. K.; Tykwinski, R. R. Angew. Chem.
Int. Ed. 2006, 45, 1034. (c) Polyynes: Synthesis, Properties,
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Raton FL, 2006. (d) Tobe, Y.; Wakabayashi, T. In
Acetylene Chemistry: Chemistry, Biology, and Material
Science; Diederich, F.; Stang, P. J.; Tykwinski, R. R., Eds.;
Wiley-VCH: Weinheim, 2005, Chap. 9. (e) Eisler, S.;
Tykwinski, R. R. In Acetylene Chemistry: Chemistry,
Biology, and Material Science; Diederich, F.; Stang, P. J.;
Tykwinski, R. R., Eds.; Wiley-VCH: Weinheim, 2005,
Chap. 7.
(14) Siemsen, P.; Livingston, R. C.; Diederich, F. Angew. Chem.
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(15) (a) Fritsch, P. Justus Liebigs Ann. Chem. 1894, 279, 319.
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(16) For recent reviews, see: (a) Chalifoux, W. A.; Tykwinski, R.
R. Chem. Rec. 2006, 6, 169. (b) Knorr, R. Chem. Rev. 2004,
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Synlett 2009, No. 13, 2068–2075 © Thieme Stuttgart · New York