9078
J. Am. Chem. Soc. 1998, 120, 9078-9079
Scheme 1
Polynaphthalene Networks from Bisphenols
Dennis W. Smith, Jr.,*,†,§ David A. Babb,†
R. Vernon Snelgrove,† Paul H. Townsend, III,‡ and
Steven J. Martin‡
Central & New Businesses R&D
The Dow Chemical Company
Freeport, Texas 77541, and Midland, Michigan 48674
ReceiVed May 6, 1998
Scheme 2
Enediynes were first studied by Bergman and are known to
undergo thermal intramolecular cyclization to benzene 1,4-
diradical or “dehydroaromatic” intermediates.1 While the primary
impetus for enediyne research remains focused on their biological
activity as antitumor agents,2 others have reported using enediynes
in a polymerization scheme.3,4 Tour detailed the synthesis of
linear poly(phenylenes) and poly(naphthalenes) by thermolysis
of substituted enediynes and 1,2-dialkynylbenzenes (Scheme 1).3
This work extended earlier accounts4 and revealed the Bergman
cyclization as a viable polymerization reaction in detail.
Polynaphthalenes prepared by Bergman cyclopolymerization
to date have been limited to linear systems of soluble, low
molecular weight oligomers with fair thermal stability, or high
molecular weight polymers exhibiting exceptional thermal stability
yet are insoluble and not easily processed.3,4 In addition, the
preparation of 1,2-dialkynyl monomers is typically accomplished
by the palladium-catalyzed coupling of terminal alkynes with
difficult to prepare 1,2-dibromo or -diiodo aromatics.3-5 We have
found, however, that bis(o-di(phenylethynyl)phenyl) monomers
1-4 (Scheme 2) overcome both monomer synthetic obstacles and
the processability/performance “tradeoff” issues common to linear
polyarylenes.6 We have developed a general multi hundred gram
preparation of these compounds in three steps from commodity
starting materials and reagents. When heated, monomers 1-4
undergo Bergman cyclopolymerization to reactive oligomers
which can be melt or solution processed and thermally cured
providing a new class of polynaphthalene networks. Other
polymers containing naphthalene linkages are also known.7 Our
polynaphthalene networks were designed specifically to replace
current dielectric materials used in integrated circuits.8
oshira-type9 palladium coupling with phenylacetylene produced
tetraynes 1-4 in isolated yields usually >80% (Scheme 2).10 Our
method does not use a copper cocatalyst, common to aryl alkyne
couplings, thereby eliminating the potentially hazardous formation
of copper acetylide.11 All monomers were isolated as lightly
colored crystalline solids with sharp melting points (Table 1).
Neat exothermic polymerizations of 1-4 are detected by
differential scanning calorimetry (DSC, 10 °C/min) at 200-210
°C, giving reaction profiles consistent with known phenyl-
substituted aryldiynes.4 For example, the polymerization of
1,2,4,5-tetrakis(phenylethynyl)benzene and poly(arylene-1,2-ethyn-
ylene) each containing four acetylene linkages, gave a DSC-
measured -∆H ) 29 kcal/mol alkyne, whereas the thermolysis
of 1-3 gave -∆H ) 27, 29, and 27 kcal/mol alkyne, respectively.
Fluorenyl monomer 4 exhibited a significantly lower -∆H ) 18
kcal/mol alkyne, due to incomplete conversion.
Bergman cyclopolymerization kinetics, and thus rheological
properties, are controlled by tetraphenyl substitution and provide
Monomer intermediates were prepared by selective o-bromi-
nation followed by quantitative trifluoromethanesulfonate (triflate)
esterification of the corresponding bisphenols and gave aryl
dibromide ditriflate intermediates in good yield (>75%). Sonog-
(7) For well-defined naphthalene polymers, see: Fahenstich, U.; Koch, K.
H.; Mu¨llen, K. Makromol. Chem. Rapid Commun. 1989, 10, 563. Pu, L.;
Wagaman, M. W.; Grubbs, R. H. Macromolecules 1996, 29, 1138. Stenger-
Smith, Sauer, J. D.; Wegner, G.; Lenz, R. W. Polymer 1990, 31, 1632. For
poly(perinaphthalene), see: Lehmann, G. Synthetic Metals 1991, 41-43, 1615.
Murkami, M. J. Appl. Phys. 1990, 67 (1), 194. Naphthalene can be
electrochemically polymerized, see: Shi, G.; Xue, G.; Li, C.; Jin, S. Polymer
Bulletin 1994, 33, 325-329. Klamann, D. In Ullmann’s Encyclopedia of
Industrial Chemistry, 5th ed., Verlag Chemie: Weinheim, 1990; Vol. A15, p
423.
(8) For a recent status, see: Mater. Res. Soc. Bull. 1997, 22 (10). Low
Dielectric Constant Materials III. Mater. Res. Soc. Symp. Proc. Case, C.;
Kohl, P.; Kikkawa, T.; Lee, W., Eds.; 1997, 476, 3-57. For low k polyimide
development, see: Hedrick, J.; Carter, K.; Richter, R.; Miller, R.; Russell,
T.; Flores, V. Chem. Mater. 1998, 10, 39.
† Dow Chemical, Freeport, TX.
‡ Dow Chemical, Midland, MI.
§ Current address: Department of Chemistry, Clemson University, Clemson,
(1) Bergman, R. G. Acc. Chem. Res. 1973, 6, 25-31. Bharucha, K. N.;
Marsh, R. M.; Minto, R. E.; Bergman, R. G. J. Am. Chem. Soc. 1992, 114,
3120. Lockhart, T. P.; Bergman, R. G. J. Am. Chem. Soc. 1981, 103, 4091.
Jones, R. R.; Bergman, R. G. J. Am. Chem. Soc. 1972, 94, 660.
(2) Nicolaou, K. C.; Dai, W.-M. Angew. Chem., Int. Ed. Engl. 1991, 30,
1387-1416. Semmelhack, M. F.; Neu, T.; Foubelo, F. J. Org. Chem. 1994,
59, 5038. Grissom, J. W.; Calkins, T. L. J. Org. Chem. 1993, 58, 5422. Jones,
G. B.; Mathews, J. E.; Li, A. Tetrahedron Lett. 1996, 37, 3643.
(3) John, J. A.; Tour, J. M. J. Am. Chem. Soc. 1994, 116, 5011. John, J.
A.; Tour, J. M. Tetrahedron 1997, 53 (45), 15515.
(4) For tetrakis(phenylethynyl)benzene, see: Sastri, S. B.; Keller, T. M.;
Jones, K. M.; Armistead, J. P. Macromolecules 1993, 26, 6171. Jones, K.
M.; Keller, T. M. Polymer 1995, 36 (1), 187. For poly(arylene-1,2-ethynylene),
see: Grubbs, R. H.; Kratz, D. Chem. Ber. 1993, 126, 149-57.
(5) Zhou, Q.; Carroll, P. J.; Swager, T. M. J. Org. Chem., 1994, 59, 1294.
Ernst, A.; Gobbi, L.; Vasella, A. Tetrahedron Lett. 1996, 37 (44), 7959-
7962.
(6) For reviews, see: Scherf, U.; Mu¨llen, K. Synthesis 1992, 23. Tour, J.
M. AdV. Mater. 1994, 6, 190. Kovacic, P.; Jones, M. B.; Chem. ReV. 1987,
87, 357. Schlu¨ter, A.-D. AdV. Mater. 1991, 3, 282. Schlu¨ter, A.-D.; Wegner,
G. Acta Polymer 1993, 44, 59-69. Percec, V.; Bae, J.-Y.; Zhao, M.; Hill, D.
H. Macromolecules 1995, 28, 6726. For water-soluble examples, see: Wallow,
T. I.; Novak, B. M. J. Am. Chem. Soc. 1991, 113, 7411. Kim, S.; Jackiw, J.;
Robinson, E.; Schanze, K. S.; Reynolds, J. R.; Baur, J.; Rubner, M. F.; Boils,
D. Macromolecules 1998, 31, 1 (4), 964.
(9) Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett. 1975, 50,
4467. Takahashi, S.; Kuroyama, Y.; Sonogashira, K.; Hagihara, N. Synthesis
1980, 8, 627. Okita, T.; Isobe, M. Tetrahedron 1995, 51 (13), 3737.
(10) Typical coupling procedure (1): To a deoxygenated solution of aryl
dibromide ditriflate (102.4 g, 0.135 mol), DMF (400 mL), triethylamine (400
mL), and [P(Ph)3]2PdCl2 (7.0 g, 0.01 mol) at 65 °C was added phenyl-
acetylene (68.0 g, 0.667 mol) dropwise in 3-10 min. The mixture was heated
at 90 °C for 2.5 h, diluted with CH2Cl2 (500 mL), washed with 10% HCl,
evaporated, and cyrstallized giving 82.6 g (87%), mp 189-191 °C. IR (cm-1):
1
2213.9 (-CCPh). H NMR (400 MHz, CDCl3): δ 7.30-7.40 (13H, br, m),
7.52-7.62 (13H, br, m). 13C NMR (100 MHz, CDCl3): δ 64.0 (hept, C(CF3)2,
J ) 30 Hz), 87.23, 87.48, 94.54, 95.38 (-CCPh) 122.77, 126.16, 126.93,
128.36, 128.40, 128.71, 128.78, 129.4, 131.63, 131.72, 132.51, 133.11. 19F
NMR (376 MHz, CDCl3): δ -63.84 (s). HRMS for C47H26F6 calcd (found):
704.1939 (704.1926).
(11) Copper-free couplings have been reported, see: Alami, M.; Ferri, F.;
Linstrumelle, G. Tetrahedron Lett. 1993, 34 (40), 6403. Chen, Q. Y.; Yang,
Z. Y. Tetrahedron Lett. 1986, 27, 1171.
S0002-7863(98)01572-8 CCC: $15.00 © 1998 American Chemical Society
Published on Web 08/19/1998