E. H. Fort, L. T. Scott / Tetrahedron Letters 52 (2011) 2051–2053
2053
and chiral carbon nanotubes cannot be grown by this method, be-
cause whatever bay regions they might have would be consumed
and not replaced by new bay regions. A corollary of this restriction
is that mixtures of hydrogen terminated carbon nanotubes sub-
jected to the benzyne growth method ought to produce elongated
armchair nanotubes exclusively and leave the zig–zag and chiral
carbon nanotubes essentially unchanged. Armchair nanotubes of
all diameters are conductive and are therefore desirable as
nanowires.14
had fully sublimed, the ovens were switched off, and the apparatus
was allowed to cool. The crude pyrolysate was taken up in DCM
and filtered to remove insoluble carbonaceous material. Column
chromatography on silica gel with 10% DCM in hexanes gave
12.6 mg (4.8%) of clean 1 in the third fraction. The spectral proper-
ties matched those of a sample prepared as described above.
Acknowledgments
In conclusion, we have demonstrated for the first time that the
Diels–Alder cycloaddition of benzyne to a PAH bay region and sub-
sequent thermal rearomatization of the cycloadduct can all be con-
ducted in a high temperature, solvent-free flow system, under
conditions that are known to promote the type of cyclodehydroge-
nation that will be necessary to grow carbon nanotubes by the
strategy outlined in Figure 1.
We thank the Department of Energy and the National Science
Foundation for financial support of this research.
References and notes
1. (a) Fort, E. H.; Donovan, P. M.; Scott, L. T. J. Am. Chem. Soc. 2009, 131, 16006–
16007; (b) Fort, E.; Scott, L. Angew. Chem., Int. Ed. 2010, 49, 6626–6628; Fort, E.
2. (a) Sirinintasak, S.; Kuwatani, Y.; Hoshi, S.; Isomura, E.; Nishinaga, T.; Iyoda, M.
Tetrahedron Lett. 2007, 48, 3433–3436. and references cited therein; (b) Herges,
R. Nachr. Chem. 2007, 55, 962–963. , 966–969; (c) Yao, T.; Yu, H.; Vermeij, R. J.;
Bodwell, G. J. Pure Appl. Chem. 2008, 80, 533–546; (d) Merner, B. L.; Dawe, L. N.;
Bodwell, G. J. Angew. Chem., Int. Ed. 2009, 48, 5487–5491; (e) Jasti, R.;
Bhattacharjee, J.; Neaton, J. B.; Bertozzi, C. R. J. Am. Chem. Soc. 2008, 130, 17646–
17647; (f) Steinberg, B. D.; Scott, L. T. Angew. Chem., Int. Ed. 2009, 48, 5400–
5402; (g) Takaba, H.; Omachi, H.; Yamamoto, Y.; Bouffard, J.; Itami, K. Angew.
Chem., Int. Ed. 2009, 48, 6112–6116; (h) Yamago, S.; Watanabe, Y.; Iwamoto, T.
Angew. Chem. Int., Ed. 2010, 49, 757–759; (i) Jasti, R.; Bertozzi, C. R. Chem. Phys.
Lett. 2010, 494, 1–7.
3. (a) Jackson, E. A.; Steinberg, B. D.; Bancu, M.; Wakamiya, A.; Scott, L. T. J. Am.
Chem. Soc. 2007, 129, 484–485; (b) Hill, T. J.; Hughes, R. K.; Scott, L. T.
Tetrahedron 2008, 64, 11360–11369; (c) Steinberg, B. D.; Jackson, E. A.; Filatov,
A. S.; Wakamiya, A.; Petrukhina, M. A.; Scott, L. T. J. Am. Chem. Soc. 2009, 131,
10537–10545.
4. Saidi-Besbes, S.; Grelet, E.; Bock, H. Angew. Chem., Int. Ed. 2006, 45, 1783–1786.
5. (a) Scott, L. T.; Bratcher, M. S.; Hagen, S. J. Am. Chem. Soc. 1996, 118, 8743–8744;
(b) Tsefrikas, V. M.; Scott, L. T. Chem. Rev. 2006, 106, 4868–4884; (c) Xue, X.;
Scott, L. T. Org. Lett. 2007, 9, 3937–3940.
6. Stork, G.; Matsuda, K. U.S. Patent 3,364,275, 1968; Chem. Abstr. 1968, 69, 10398.
7. Gilchrist, T. L. Sci. Synth. 2008, 43, 151–224.
8. (a) Zhi, L.; Müllen, K. J. Mater. Chem. 2008, 18, 1472–1484; (b) Rempala, P.;
Kroulik, J.; King, B. T. J. Org. Chem. 2006, 71, 5067–5081; (c) King, B. T.; Kroulik,
J.; Robertson, C. R.; Rempala, P.; Hilton, C. L.; Korinek, J. D.; Gortari, L. M. J. Org.
Chem. 2007, 72, 2279–2288.
9. Evidence for the Diels–Alder cycloaddition of benzyne to benzene in the gas
phase has been obtained by copyrolysis of phthalic anhydride and C6D6:
Friedman, L.; Lindow, D. F. J. Am. Chem. Soc. 1968, 90, 2329–2333.
10. (a) Brown, R. F. C.; Gardner, D. V.; McOmie, J. F. W.; Solly, R. K. Aust. J. Chem.
1967, 20, 139–148; (b) Barry, M.; Brown, R. F. C.; Eastwood, F. W.;
Gunawardana, D. A.; Vogel, C. Aust. J. Chem. 1984, 37, 1643–1657; (c) Brown,
R. F. C.; Coulston, K. J.; Eastwood, F. W.; Vogel, C. Aust. J. Chem. 1988, 41, 1687–
1695.
3. Experimental section
3.1. Naphtho[1,2,3,4-ghi]perylene (1), in solution (Scheme 1b)
To a 50 mL two-necked round bottomed flask equipped with a
reflux condenser and under nitrogen, 50 mg (0.20 mmol) of pery-
lene and 1.24 g (4.0 mmol) of tetrabutylammonium fluoride trihy-
drate (TBAF) were added. To this was added 1 mL of dry toluene,
and the reaction mixture was heated to reflux. To this reaction
mixture was added, dropwise from a syringe at a rate of approxi-
mately 8 mL/h, a solution of 0.96 lL (4.0 mmol) of 2-(trimethyl-
silyl)phenyl trifluoromethanesulfonate in 8 mL of toluene. After
completion of the addition, the reaction mixture was maintained
at reflux for an additional 1.5 h and was then allowed to cool to
room temperature. The mixture was diluted with dichloromethane
(DCM); the solution was washed with 3 Â 300 mL of H2O, and the
organic solvent was then removed under reduced pressure. The
resulting solid was digested in ethanol and filtered to yield
28.8 mg (45%) of 1 as a yellow solid. The spectroscopic properties
of 1 matched those of a sample prepared previously by an indepen-
dent synthesis.5c
3.2. Naphtho[1,2,3,4-ghi]perylene (1), in the gas phase
(Scheme 2)
A solid mixture of 200 mg (0.79 mmol) of perylene and 1.18 g
(8.0 mmol) of phthalic anhydride was divided into two portions.
The portions were homogenized individually by ball-milling for
5 min each and were then recombined in a quartz boat, which
was inserted into the capped end of the quartz pyrolysis tube.
The system was pumped down to 0.5 mmHg. The sublimation oven
was then turned on and allowed to equilibrate to 500 °C, while the
reaction oven was turned on and allowed to equilibrate to 1000 °C.
The boat was then quickly moved to the middle of the sublimation
oven.15 The temperature of the reaction oven temporarily dropped
by approximately 10 °C, and the pressure shot off-scale as the
material sublimed rapidly, but the pressure returned to below
1.0 mmHg within approximately 90 s. Once the starting materials
11. For a detailed description of the apparatus and procedure, see Necula, A.; Scott,
L. T. J. Anal. Appl. Pyrol. 2000, 54, 65–87. and Ref. 5b.
12. Copyrolysis experiments such as this have previously been used to generate
and trap aryl radicals in the gas phase: Necula, A.; Scott, L. T. J. Am. Chem. Soc.
2000, 122, 1548–1549.
13. (a)Carbon Nanotubes Synthesis; Dresselhaus, M. S., Dresselhaus, G., Avouris, P.,
Eds.Structure, Properties, and Applications, Topics in Current Physics; Springer:
Berlin/Heidelberg, 2001; Vol. 80, (b) Povitsky, A. Int. J. Nanosci. 2005, 4, 73–98.
14. Collins, P. G.; Avouris, P. Sci. Am. 2000, 283, 62–69.
15. To provide a means for moving the boat inside the pyrolysis tube without
having to break the vacuum, a magnet was placed inside the tube behind the
boat during the original set up; the magnet inside the tube could then be
manipulated by a magnet outside the tube and used to reposition the boat in
the tube.