Synthesis and solid-state structure of perfluorophenyl end-capped polyynes

Article abstract of DOI:10.1021/ol800583r

(Chemical Equation Presented) Five new supramolecular building blocks have been synthesized on the basis of polyynes end-capped with pentafluorophenyl groups, including three symmetrical (16, 17, 18) and two unsymmetrical polyynes (7 and 12). The solid-st

Full text of DOI:10.1021/ol800583r

ORGANIC
LETTERS
2008
Vol. 10, No. 11
2163-2166
Synthesis and Solid-State Structure of
Perfluorophenyl End-Capped Polyynes
Jamie Kendall, Robert McDonald, Michael J. Ferguson, and Rik R. Tykwinski*
Department of Chemistry, UniVersity of Alberta, Edmonton AB T6G 2G2, Canada
rik.tykwinski@ualberta.ca
Received March 13, 2008
ABSTRACT
Five new supramolecular building blocks have been synthesized on the basis of polyynes end-capped with pentafluorophenyl groups, including
three symmetrical (16, 17, 18) and two unsymmetrical polyynes (7 and 12). The solid-state behavior of these molecules based on the attractive
electrostatic interactions of the phenyl and perfluorophenyl groups has been examined by X-ray crystallographic analysis of 7, 12, and 16·25.
In 1960, Patrick and Prosser discovered that the admixture
of benzene and hexafluorobenzene resulted in a room-
temperature solid that was unique from either of its constitu-
ent parts.1 It has subsequently been confirmed both experi-
mentally and theoretically that benzene and perfluorobenzene
have quadrupolar moments that are nearly equal in magni-
tude, but opposite in sign.2 The result is a motif that allows
one to realize supramolecular structures in which solid-state
organization can be engineered based on the electrostatic
interactions of phenyl and perfluorophenyl groups.3
In terms of the known acetylenic derivatives 1-6,4 Grubbs
and co-workers first established that attractive interactions
between phenyl perfluorophenyl groups could also be used
to direct the solid-state packing of diynes 3·4 and 6.5 It has
been suggested that this packing motif might lead to a
productive topochemical polymerization reaction based on
interatomic orientations that arise from close packing in
molecular crystals derived from 3·4 or 6,6 although this fact
remains to be proven. It has also been recently established
by Marder and co-workers that the packing for tolan
derivatives 1·2 and 5 is also dominated by the same
supramolecular forces found for diyne derivatives 3·4 and
6.4e
Our work with extended polyynes7 led us to consider why
longer polyynes with perfluorophenyl units had not been
synthesized and studied. It became clear quite quickly that
the electrophilic nature of the perfluorophenyl group would
likely make the assembly of such molecules a synthetic
challenge.4e,8 Intrigued by this challenge, we sought to
(2) (a) Vanspeybrouck, W.; Herrebout, W. A.; van der Veken, B. J.;
Lundell, J.; Perutz, R. N. J. Phys. Chem. B 2003, 107, 13855–13861. (b)
Pe´rez-Casas, S.; Herna´ndez-Trujillo, J.; Costas, M. J. Phys. Chem. B 2003,
107, 4167–4174. (c) Williams, J. H. Acc. Chem. Res. 1993, 26, 593–598.
(3) For reviews, see: (a) Hunter, C. A.; Lawson, K. R.; Perkins, J.; Urch,
C. J. J. Chem. Soc., Perkin Trans. 2 2001, 651–669. (b) Dahl, T. Acta Chem.
Scand. 1988, 42, 1–7.
(4) For examples based on acetylenic derivatives, see: (a) Shu, L.; Mu,
Z.; Fuchs, H.; Chi, L.; Mayor, M. Chem. Commun. 2006, 1862–1863. (b)
Collings, J. C.; Burke, J. M.; Smith, P. S.; Batsanov, A. S.; Howard, J. A. K.;
Marder, T. B. Org. Biomol. Chem. 2004, 2, 3172–3178. (c) Shu, L.; Mayor,
M. Chem. Commun. 2006, 4134–4136. (d) Taylor, T. J.; Gabbai, F. P.
Organometallics 2006, 25, 2143–2147. (e) Smith, C. E.; Smith, P. S.;
Thomas, R. L.; Robins, E. G.; Collings, J. C.; Dai, C.; Scott, A. J.; Borwick,
S.; Batsanov, A. S.; Watt, S. W.; Clark, S. J.; Viney, C.; Howard, J. A. K.;
Clegg, W.; Marder, T. B. J. Mater. Chem. 2004, 14, 413–420. (f) 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–
3063. (g) Gdaniec, M.; Jankowski, W.; Milewska, M. J.; Polonski, T. Angew.
Chem., Int. Ed. 2003, 42, 3903–3906. (h) Xu, R.; Gramlich, V.; Frauenrath,
H. J. Am. Chem. Soc. 2006, 128, 5541–5547.
(5) Coates, G. W.; Dunn, A. R.; Henling, L. M.; Dougherty, D. A.;
Grubbs, R. H. Angew. Chem., Int. Ed. Engl. 1997, 36, 248–251.
(6) For a description of such reactions, see: Szafert, S.; Gladysz, J. A.
Chem. ReV. 2003, 103, 4175–4205.
(1) Patrick, C. R.; Prosser, G. S. Nature (London) 1960, 187, 1021–
1021.
10.1021/ol800583r CCC: $40.75
Published on Web 05/06/2008
2008 American Chemical Society

Scheme 2
Figure 1. Known decafluoro- and pentafluorodiphenyl mono- and
diynes.
construct perfluorophenyl polyynes and to determine if the
solid-state behavior that had been observed for mono- and
diynes 1-6 would extend to longer derivatives. We report
herein the results of our efforts.
The synthesis of pentafluorodiphenyltriyne 7 (Scheme 1)
proved to be more challenging than expected. As in previous
frustratingly unsuccessful and resulted only in the formation
of baseline material. Nevertheless, with ketone 11 in hand,
the reaction with lithium trimethylsilyldiazomethane was
attempted.12 Satisfyingly, this provided for the desired
carbenoid intermediate and subsequent rearrangement to form
triyne 7. To our knowledge, this is the first reported example
of polyyne formation using Colvin’s reagent.12
Scheme 1
As encountered in efforts toward triyne 7, attempts to form
the unsymmetrical tetrayne 12 via a FBW rearrangement
from a dibromoolefinic precursor were not successful, even
using methods successful for the formation of other tetra-
ynes.7 Thus, an alternative approach was sought. The
formation of diyne 13 was readily developed from pentafluo-
robenzoyl chloride.13 Desilylation with tetrabutylammonium
fluoride (TBAF) at 0 °C gave the deprotected diyne 14, and
reaction with bromodiyne 15 (excess) under Cadiot-
Chodkiewicz conditions14 gave 12 in good yield.
Diyne 13 also, obviously, provided the basis for synthesis
of symmetrical tetrayne 16 (eq 1). Thus, desilylation with
TBAF at low temperature gave the terminal diyne, which
was immediately subjected to Hay oxidative homocoupling.15
The desired tetrayne 16 was isolated as a stable yellow solid
in 50% yield over the two steps.
triyne synthesis,7 a carbenoid Fritsch-Buttenberg-Wiechell
(FBW) rearrangement9 with dibromoolefin 8 was planned
to form the polyyne core. Thus, the acylation reaction10 of
trimethylsilylalkyne 98,11 with excess acid chloride 10 readily
gave ketone 11 in good yield. All attempts toward forming
8 under typical dibromoolefination conditions were, however,
The synthesis of hexayne 17 and octayne 18 (Scheme 3)
began from 9 and followed similar paths. A Friedel-Crafts
(7) For recent examples of polyyne formation using the FBW rear-
rangement, see: (a) Chalifoux, W. A.; Tykwinski, R. R. Chem. Rec. 2006,
6, 169–182. (b) Luu, T.; Elliott, E.; Slepkov, A. D.; Eisler, S.; McDonald,
R.; Hegmann, F. A.; Tykwinski, R. R. Org. Lett. 2005, 7, 51–54. (c) Eisler,
S.; Slepkov, A. D.; Elliott, E.; Luu, T.; McDonald, R.; Hegmann, F. A.;
Tywkinski, R. R. J. Am. Chem. Soc. 2005, 127, 2666–2676. (d) 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, Germany, 2005. (e) Eisler, S.; Chahal, N.; McDonald, R.;
Tykwinski, R. R. Chem. Eur. J. 2003, 9, 2542–2550.
(12) Colvin, E. W.; Hamill, B. J. J. Chem. Soc., Perkin Trans. 1 1977,
869–874.
(13) See Supporting Information for details.
(14) Cadiot, P.; Chodkiewicz, W. In Chemistry of Acetylenes; Viehe,
H. G., Ed.; Marcel Dekker: New York, 1969; pp 597-647. For recent
examples of polyyne formation using the Cadiot-Chodkiewicz method,
see: Lee, S.; Lee, T.; Lee, Y. M.; Kim, D.; Kim, S. Angew Chem., Int. Ed.
2007, 46, 8422–8425. (c) Sabitha, G.; Reddy, C. S.; Yadav, J. S. Tetrahedron
Lett. 2006, 47, 4513–4516. (d) Gung, B. W.; Kumi, G. J. Org. Chem. 2003,
68, 5956–5960.
(8) Zhang, Y.; Wen, J. Synthesis 1990, 727–728.
(9) (a) Fritsch, P. Liebigs Ann. Chem. 1894, 279, 319–323. (b)
Buttenberg, W. P. Liebigs Ann. Chem. 1894, 279, 324–337. (c) Wiechell,
H. Liebigs Ann. Chem. 1894, 279, 337–344. (d) For a recent review, see:
Knorr, R. Chem. ReV. 2004, 104, 3795–3849.
(15) Hay, A. S. J. Org. Chem. 1962, 27, 3320–3321. For recent examples
of polyyne formation using the Hay and similar methods, see: de Quadras,
L.; Bauer, E. B.; Mohr, W.; Bohling, J. C.; Peters, T. B.; Mart´ın-Alvarez,
J. M.; Hampel, F.; Gladysz, J. A. J. Am. Chem. Soc. 2007, 129, 8296–
8309. Simpkins, S. M. E.; Weller, M. D.; Cox, L. R. Chem. Commun. 2007,
4035–4037. Zheng, Q.; Bohling, J. C.; Peters, T. B.; Frisch, A. C.; Hampel,
F.; Gladysz, J. A. Chem. Eur. J. 2006, 12, 6486–6505. Gibtner, T.; Hampel,
F.; Gisselbrecht, J.-P.; Hirsch, A. Chem. Eur. J. 2002, 8, 408–432.
(10) Walton, D. R. M.; Waugh, F. J. Organomet. Chem. 1972, 37, 45–
56.
(11) Chen, Q.-Y.; Li, Z.-T. J. Chem. Soc., Perkin Trans. 1 1992, 2931–
2934
.
2164
Org. Lett., Vol. 10, No. 11, 2008

Scheme 3
Table 1. Melting Point (°C) Comparisons for Phenyl and
Perfluorophenyl Polyynes
Ph-(CC)n-Ph +
n
Ph-(CC)n-Ph PhF-(CC)n-PhF PhF-(CC)n-PhF Ph-(CC)n-PhF
a
1
2
3
4
6
8
58.5-5917
875
123-123.518
1145
104-1054e
1245
154-155
125-126
n.a.
1525
n.a.
133-134
n.a.
91-9217
n.a.b
109-11019 174-176c
133c,d
85c,d
133-134c
99c
n.a.
n.a.
a The 1:1 cocrystal has been reported, but no melting point was provided,
see ref 4e. b n.a.: not available. c Decomposition point. d Determined by
differential scanning calorimetry.7b
logues, even though the number of favorable phenyl-
perfluorophenyl interactions is essentially identical in each
case.
Crystals of triyne 7 were grown from a solution of CHCl3
at room temperature (Figure 2).20 The individual molecules
acylation with 19 gave the corresponding ynone (not shown),
which was purified and then readily converted to dibro-
moolefin 20.16 The analogous reaction sequence of acylation
and dibromoolefination starting with TIPS-protected 21
ultimately gave 22, albeit in low yield over the two steps
(using the TBDMS analogue of 21 failed to give product).
FBW rearrangement of 20 and 22 then gave the triyne 23
and tetrayne 24, respectively, in decent yields. Finally,
desilylation and oxidative homocoupling under Hay condi-
tions gave the desired polyynes 17 and 18.
The characterization of extended polyynes 7, 12, and
16-18 by 19F NMR spectroscopy is particularly diagnostic,
showing second order multiplets for the ortho and meta
fluorine atoms at ca. -139 and -162 ppm (due to coupling
with other magnetic nonequivalent F-atoms of the aryl ring).
The signal of the para fluorine is typically observed as a
triplet of triplets, centered at -153 ppm. The 13C NMR
spectroscopic characterization of polyynes 7 and 12, as well
as many of their precursors, is complicated by an inability
Figure 2. Solid-state orientation of 7 for four neighboring
molecules; center-to-center distances d (20% probability level).
1
to effect both H and 19F decoupling in a single NMR
experiment. Nevertheless, all spectra and observed coupling
patters are consistent with the proposed structures.13 The
MALDI MS analysis of octayne 18 is noteworthy. In addition
to the signal observed at m/z 526 for M+, additional signals
are essentially planar, with a dihedral angle between planes
formed of terminal aryl rings of only 4.61(7)°. The triyne
segment is nearly linear, with acetylenic bond angles that
range from 178.8(2) to 179.8(3)°. Neighboring molecules
stack to form centrosymmetric, dimeric pairs, separated by
3.46 Å.21 The stacking of neighboring pairs is slightly offset,
although still separated by 3.47 Å. The center-to-center
distances of d ) 3.68 and d ) 3.71 Å are analogous to those
were found for the dimer (2M+ ) 1052), trimer (3M+
)
1578), tetramer (4M+ ) 2104), and pentamer (5M+ ) 2630),
showing aggregation or chemical cross-linking during the
analysis.13
The observed melting points for phenyl and perfluorophen-
yl polyynes are summarized in Table 1, in comparison to
several known molecules. In general, the decafluoro (PhF-
(CC)n-PhF) and pentafluoro (Ph-(CC)n-PhF) polyynes show
higher melting points than the analogous diphenyl polyynes.
Likewise, for the two known systems, n ) 2 and n ) 4, the
1:1 cocrystals of PhF-(CC)n-PhF and Ph-(CC)n-Ph are higher
melting solids than the corresponding Ph-(CC)n-PhF ana-
(17) Rubin, Y.; Lin, S. S.; Knobler, C. B.; Anthony, J.; Boldi, A. M.;
Diederich, F. J. Am. Chem. Soc. 1991, 113, 6943–6949.
(18) Birchall, J. M.; Bowden, F. L.; Haszeldine, R. N.; Lever, A. B. P.
J. Chem. Soc. A 1967, 747–753.
(19) Armitage, J. B.; Entwistle, N.; Jones, E. R. H.; Whiting, M. C.
J. Chem. Soc. 1954, 147–154.
(20) X-ray crystallographic data for 7: C18H5F5, M ) 316.22, triclinic
j
space group P1 (No. 2); a ) 7.3722(6) Å, b ) 7.9609(10) Å, c ) 13.2604
(12) Å; R ) 101.447(9)°, ꢀ ) 91.357(7)°, γ ) 114.541(7)°; V ) 688.93(12)
(16) (a) Ramirez, F.; Desai, N. B.; McKelvie, N. J. Am. Chem. Soc.
1962, 84, 1745–1747. (b) Corey, E. J.; Fuchs, P. L. Tetrahedron Lett. 1972,
3769–3772.
Å3; Z ) 2; Fcalcd )1.524 g cm-3, µ ) 0.136 mm-1; T ) -80 °C. Final R1
2
2
) 0.0453 (1881 observations [Fo g 2σ(Fo )]); wR2 ) 0.1266 for 209
2
2
variables and 2838 data with [Fo g -3σ(Fo )]; CCDC 677133.
Org. Lett., Vol. 10, No. 11, 2008
2165

found for 6. Thus, the packing of 7 is very similar to the
motif observed for the corresponding mono- and diyne
analogues 54e and 6.5
Crystals of the next highest homologue of this series,
tetrayne 12, were grown from a mixture of CCl4 and
cyclohexane at room temperature (Figure 3).22 The conju-
Figure 4. Solid-state orientation of 16·25 for four neighboring
molecules; center-to-center distances d (20% probability level).
16 and 25 are nearly linear, with all acetylenic bond angles
between 177.5(2) and 179.6(3)°. The alternate stacking of
16·25 mirrors that found in 1:1 mixtures of both 1·24e and
3·4,5 and the center-to-center distances for the tetraynes of
d ) 3.68 Å is nearly identical to those observed for 3·4 (d
) 3.69 Å).5 Thus, the length of the acetylenic linker appears
to play little role in the packing found in these cocrystalline
pairs 1·2, 3·4, and 16·25.
Figure 3. Solid-state orientation of 12 for four neighboring
molecules; center-to-center distances d (20% probability level).
In conclusion, five new perfluoroaryl polyynes have been
synthesized and the solid-state packing examined by X-ray
crystallography for three examples. These crystallographic
analyses show that the supramolecular packing motif docu-
mented previously for the shorter mono- and diacetylenic
derivatives is maintained almost identically in the longer
analogues (7, 12, and 16·25) studied here.
gated framework of 12 is nearly planar, with a dihedral angle
between planes formed of terminal aryl rings of 4.67(12)°.
The polyyne segment is basically linear, with acetylenic bond
angles that range from 177.8(4) to 179.4(3)°. Two nearest
neighbor molecules form a centrosymmetric dimeric pair
separated by an interplanar distance of 3.46 Å, and successive
pairs are stacked at the same distance of (3.47 Å). The center-
to-center separation for the tetraynes is d ) 3.67 and d )
3.73 Å, again comparable to 6 and 7. Thus, the solid-state
packing for polyynes 7 and 12, in comparison to 5 and 6,
shows that polyyne length has a negligible effect on the
supramolecular organization of these molecules in the solid
state.
Acknowledgment. This work has been generously sup-
ported by the University of Alberta and the Natural Sciences
and Engineering Research Council of Canada (NSERC)
through the Discovery Grant program.
Supporting Information Available: Experimental pro-
cedures, spectroscopic data, and copies of NMR spectra for
new compounds. Copies of mass spectra for polyynes 7, 12,
and 16-18. CIF file for crystallographic structures. This
material is available free of charge via the Internet at
http://pubs.acs.org.
Cocrystals of 16 and diphenyl-1,3,5,7-octatetrayne
(25)7b,19,23 were grown from a 1:1 mixture of the two
compounds in MeOH at room temperature (Figure 4).24 Both
(21) Intermolecular distances are based on the separation of planes
generated from all non-hydrogen atoms of neighboring molecules using
Mercury 1.3; see the Supporting Information for more details.
OL800583R
(22) X-ray crystallographic data for 12: C20H5F5, M ) 340.24; triclinic
space group P1 (No. 2); Fc ) 1.470 g cm-3; a ) 7.3896(12) Å, b )
j
7.9448(13) Å, c ) 14.452(2) Å; R ) 91.906(3)°, ꢀ ) 94.375(3)°, γ )
(24) X-ray crystallographic data for 16·25: C40H10F10, M ) 680.48;
114.390(2)°; V ) 768.5(2) Å3; Z ) 2; µ ) 0.128 mm-1. Final R(F) )
triclinic space group P1 (No. 2); Fc ) 1.483 g cm-3; a ) 7.3625(10) Å, b
j
2
0.0710 (1522 observations [Fo2 g 2σ(Fo )]); wR2 ) 0.2125 for 226 variables
) 7.8987(11) Å, c ) 14.684(2) Å; R ) 82.017(2)°, ꢀ ) 80.119(2)°, γ )
2
2
and 2702 data with [Fo g -3σ(Fo )]; CCDC 677134.
65.267(2)°; V ) 761.97(18) Å3; Z ) 1; µ ) 0.129 mm-1. Final R(F) )
2
(23) Haley, M. M.; Bell, M. L.; Brand, S. C.; Kimball, D. B.; Pak, J. J.;
0.0413 (1910 observations [Fo2 g 2σ(Fo )]); wR2 ) 0.1386 for 226 variables
2
2
Wan, W. B. Tetrahedron Lett. 1997, 38, 7483–7486
.
and 2969 data with [Fo g -3σ(Fo )]; CCDC 677135.
2166
Org. Lett., Vol. 10, No. 11, 2008