Diindeno[1,2,3,4-defg;1′,2′,3′,4′-mnop]chrysenes: Solution-phase synthesis and the bowl-to-bowl inversion barrier

Article abstract of DOI:10.1039/c0cc01730b

Diindeno[1,2,3,4-defg;1′,2′,3′,4′-mnop]chrysenes 2 were straightforwardly prepared in around 20% yield from 9,10- diarylphenanthrenes 3 by palladium-catalyzed intramolecular arylations. The bowl-to-bowl inversion barrier for buckybowl 2-iPr is predicted to be approximately 7 kcal mol^-1 based on density functional theory calculations and this value is consistent with the results of a variable-temperature ¹H-NMR study.

Full text of DOI:10.1039/c0cc01730b

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Diindeno[1,2,3,4-defg;10,20,30,40-mnop]chrysenes: solution-phase synthesis
and the bowl-to-bowl inversion barrierwz
Hung-Ing Chang,a Hsin-Ting Huang,a Cheng-Hao Huang,b Ming-Yu Kuob and
Yao-Ting Wu*a
Received 3rd June 2010, Accepted 9th July 2010
DOI: 10.1039/c0cc01730b
Diindeno[1,2,3,4-defg;10,20,30,40-mnop]chrysenes 2 were straight-
forwardly prepared in around 20% yield from 9,10-di-
arylphenanthrenes
3 by palladium-catalyzed intramolecular
arylations. The bowl-to-bowl inversion barrier for buckybowl
2-iPr is predicted to be approximately 7 kcal molꢀ1 based on
density functional theory calculations and this value is consistent
1
with the results of a variable-temperature H-NMR study.
Diindeno[1,2,3,4-defg;10,20,30,40-mnop]chrysene (2-H) is a bowl-
shaped molecule with interesting properties (Scheme 1).1 Its
curvature and the Clar aromatic sextet theory2 reveal that the
central 6 : 6-bond has the greatest reactivity of any of its
bonds, and undergoes 1,2-addition with both electrophilic
and nucleophilic reagents to give fullerene-type adducts.3
Buckybowl 2-H has been successfully obtained in 37% yield
by the flash vacuum pyrolysis (FVP) of 1,10-dibromo-
bifluorenylidene (1-Br) at 1050 1C.4 However, peripherally
substituted molecules 2 have not yet been synthesized. These
compounds could not be accessed from the parent compound
2-H because of the high reactivity of the central 6 : 6-bond.
Scheme 1 Synthesis of buckybowl 2-R.
precursor 5-Cl cannot be easily prepared, phenanthrene 3 may
straightforwardly form 2-H by a three-fold intramolecular
arylation. The efficiency of the proposed synthetic approach
should strongly depend on the cyclization sequence. In this
investigation, reaction conditions for the construction of bucky-
bowls 2-R are optimized and their bowl-to-bowl inversion
barriers are explored.
Using Larock’s protocol,9 phenanthrene 3-H was generated
in 63% yield by the palladium-catalyzed cycloaddition of
2-iodobiphenyl (7-H) with 2,20,6-trichlorodiphenylethyne
(8, Scheme 2). The precursor 3-H was cyclized in dimethyl-
ace-tamide (DMAc) at 160 1C by treating with a mixture of
Pd(PCy3)2Cl2 and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU),6a
but the result was unsatisfactory (Entry 1, Table 1). According
As
a result, the functional group must be introduced
before the backbone is formed. The currently successful FVP
protocol cannot be used in the preparation of functionalized
buckybowls 2 because the high temperature reaction conditions
affect almost all functional groups and may cause thermal
rearrangement of the molecular framework.5 Mild reaction
conditions (in the solution phase) may be able to solve this
problem. Palladium-catalyzed intramolecular arylations are
ideal for replacing FVP.6 Indeed, attempts have been made
to prepare 2-H from 1,10-dichlorobifluorenylidene (1-Cl).7
Unfortunately, only the intermediate 4-Cl and its dechlorinated
byproduct 4-H were generated. Perhaps the formation of the
final six-membered ring is inefficient under mild conditions
(ca. 120 1C).8 The closure of the five-membered ring in 5-Cl
should be easier than the route described above. Although the
1
to the H-NMR analysis, the desired 2-H was indeed formed
in small amounts, accompanied by reductive dechlorinated
byproducts 4-H and 5-H. Therefore, the reaction conditions
were systematically optimized by screening with numerous
palladium complexes, bases, solvents and reaction tempera-
tures. The catalyst Pd(PCy3)2Cl2 was observed to be more
effective than other Pd complexes that are shown in Table 1.
Although increasing the reaction temperature ensured that 3-H
was completely consumed, reductive dechlorinated inter-
mediates 4-H, 5-H and 6 then became significant, reducing
the amount of 2-H obtained. This serious problem can
be reduced somewhat by carrying out the reaction in
a Department of Chemistry, National Cheng Kung University,
No.1 Ta-Hsueh Road, 70101 Tainan, Taiwan.
E-mail: ytwuchem@mail.ncku.edu.tw; Fax: +886-6-2740552
b Department of Applied Chemistry, National Chi Nan University,
No. 1, University Rd., 54561 Puli, Nantou, Taiwan
w Metal-Catalyzed Reactions of Alkynes, Part VII. Part VI: T.-C. Wu,
C.-H. Chen, D. Hibi, A. Shimizu, Y. Tobe, Y.-T. Wu, Angew. Chem.,
Int. Ed., accepted. This work was supported by the National Science
Council of Taiwan (NSC 98-2113-M-006-002-MY3 and NSC-96-2113-
M-260-006-MY2) and the National Center for High-performance
Computing (NCHC).
z Electronic supplementary information (ESI) available: Experimen-
tal, spectral data and computational results. See DOI: 10.1039/
c0cc01730b
Scheme 2 Synthesis of phenanthrenes 3-R. Yields: R = H (63%);
R = iPr (65%; 3-iPr:30-iPr = 10 : 1)
c
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Chem. Commun., 2010, 46, 7241–7243 7241

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Table 1 Optimization of reaction conditions for synthesis of buckybowl 2-H from phenanthrene 3-Ha
Entry
Catalyst
Base
T/1C
2-H : 3-H : 4-H : 5-H
1
2
3
4
5
6
7
8
Pd(PCy3)2Cl2
Pd(PCy3)2Cl2
Pd(PCy3)2Cl2
Pd(PCy3)2Cl2
Pd(PCy3)2Cl2
Pd(PCy3)2Cl2
Pd(PCy3)2Cl2
Pd(PCy3)2Cl2
Pd(PCy3)2Cl2
Pd(OAc)2/2PCy3
Pd(OAc)2/2IPrꢁHCl
Palladacycle
DBU
DBU
DBU
DBU
DABCO
Proton sponge
K2CO3
Cs2CO3
DBU/Cs2CO3
DBU
160
170
170
150
180
180
180
180
150
180
180
180
180
180
1 : 91 : 4 : 4
3 : 61 : 14 : 19
10 : 0 : 45 : 45b
8 : 0 : 46 : 46b
1 : 96 : 0 : 3
3 : 68 : 0 : 29
0 : 67 : 0 : 33
0 : 0 : 0 : 40(:60)c
33 : 0 : 0 : 67b
0 : 98 : 0 : 2
8 : 74 : 0 : 18
0 : 98 : 0 : 2
7 : 64 : 0 : 29
0 : 99 : 0 : 1
9
10
11
12
13
14
DBU
DBU
DBU
DBU
d
[(IPr)(C10H6O2)Pd]2
[(IMes)(C10H6O2)Pd]2
e
a
A mixture of 3-H (30 mg), Pd catalyst (25.0 mmol, 60 mol%), ligand (1.2 equiv.), base (3 equiv.) and DMAc (2.0 mL) in a thick-walled sealed tube
was heated at 170 1C for 3 d. The ratio of compounds in the crude product was determined by 1H-NMR analysis. Reaction conducted in NMP
for 2 d. Amount of compound 6 in parentheses. 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene(1,4-naphthoquinone)palladium(0) dimer.
b
c
d
e
1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene(1,4-naphthoquinone)palladium(0) dimer.
N-methylpyrrolidinone (NMP) at 150 1C. DBU was a better
base than 1,8-bis(dimethylamino)naphthalene (proton sponge),
1,4-diazabicyclo[2.2.2]octane (DABCO), K2CO3 and Cs2CO3
(Entries 4–8, Table 1). Notably, the base used affected the
cyclization sequence. Unlike other bases, Cs2CO3 generated a
mixture of 5-H and 6, but no 4-H. In light of this fact, a mixed
base (DBU/Cs2CO3) was employed, and 2-H was indeed
enriched. Shortening reaction time (to two days) also reduced
the decomposition of 2-H. High catalyst loading (60 mol%)
was required to maximize the yield. Under the optimized
conditions (Entry 9 in Table 1), 2-H was obtained in 21%
yield. Furthermore, the isolation of the desired product
generated by the developed protocol is easier than that by
the FVP protocol.4a
and mostly phenanthrene 3-iPr was obtained (Scheme 2).
Cyclization of the mixture of 3-iPr and 30-iPr under our
optimized conditions gave the desired 2-iPr in 19% yield.
Variable-temperature NMR experiments were performed
using a 500 MHz instrument. At room temperature, 2-iPr
exhibits a sharp doublet associated with the methyl groups,
but at 193 K, it becomes a broad singlet (see ESIz). The
coalescence temperature of the signal was expected to be
slightly lower than this temperature. The NMR studies
demonstrate that two bowl forms contribute to an equilibrium
structure and DGa of 2 should be very small.
inv
Density functional theory (DFT) calculations were per-
formed to examine the bowl-to-bowl inversion of 2-H and
other buckybowls, such as 2-iPr, 9-H and 10 (Chart 1,
Table 2).z The geometry optimizations and frequencies of
the molecules were calculated at the B3LYP/cc-pVDZ and
M06-2X/cc-pVDZ levels using the Gaussian 09 Program.11
The computational results of these compounds fitted the
Compound 2-iPr was selected to investigate the bowl-to-
bowl inversion barrier (DGainv).10 It was prepared in the same
manner as 2-H. The cycloaddition of 2-iodo-4-isopropyl-
biphenyl (7-iPr) with alkyne 8 provided high regioselectivity,
Chart 1
Table 2 Properties and structures of selected bowl-shaped molecules
Exptl.
B3LYP/cc-pVDZ
M06-2X/cc-pVDZ
Coalescence
T/K
DGa
/
DGa
/
Bowl
depth/A
DGa
/
inv
Bowl
depth/A
inv
inv
kcal molꢀ1
Max. POAV/1
Bowl depth/A
1.440
Ref.
kcal molꢀ1
kcal molꢀ1
2-H
2-iPr
9-H
9-iPr
10
—
o193
—
o10
9.0
4a
5.8
6.1
1.334
1.358
6.9
7.2
9.9
1.384
1.410
0.886
—
—
8.2
9.0
0.87
15
12a
13,16
9.1 (9.2a)
0.874 (0.877a)
242
413
11.3
19.6
1.112
18.2
1.142
1.156
a
Ref. 12c.
c
7242 Chem. Commun., 2010, 46, 7241–7243
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crystal structures and experimental data very closely. For
B. D. Steinberg, M. Bancu, A. Wakamiya and L. T. Scott, J. Am.
Chem. Soc., 2007, 129, 484.
7 S. Pogodin, P. U. Biedermann and I. Agranat, J. Org. Chem., 1997,
62, 2285.
8 Oxidative electrocyclization of compounds 1-H, 4-H or 5-H cannot
generate buckybowl 2-H, see: (a) N. S. Mills, J. L. Malandra,
A. Hensen and J. A. Lowery, Polycyclic Aromat. Compd., 1998, 12,
239; (b) C.-H. Kuo, M.-H. Tsau, D. T.-C. Weng, G. H. Lee,
S.-M. Peng, T.-Y. Luh, P. U. Biedermann and I. Agranat, J. Org.
Chem., 1995, 60, 7380.
2-iPr, DGa is calculated to be 6.11 kcal molꢀ1 by B3LYP,
inv
whereas the value is 7.2 kcal molꢀ1 with the same basis set
using M06-2X. These computations are consistent with the VT
NMR studies. Either experimental or computational results
indicated that DGainv of 2 is smaller than that of corannulene
(9)12 and sumanene (10).13
The degree of the bowl shape of the buckybowls can be
determined not only by DGainv, but also from the bowl depth
and the POAV (p-orbital axis vector) pyramidalization angle
of the structure.14 Unlike other bowl-shaped molecules, such
as corannulene (9)15 and sumanene (10),16 compounds 2 have
larger POAV pyramidalization angles and bowl depths, but
9 R. C. Larock, M. J. Doty, Q. Tian and J. M. Zenner, J. Org.
Chem., 1997, 62, 7536.
10 The calculated activation energies for the bowl-to-bowl inversions
of 2-H was predicated to be 14.1 and 6.8 kcal molꢀ1 based on the
PM3 parameter set and B3LYP/6-311G** level, respectively, see:
(a) S. Hagen, H. Christoph and G. Zimmermann, Tetrahedron,
1995, 51, 6961; (b) P. U. Biedermann, S. Pogodin and I. Agranat,
J. Org. Chem., 1999, 64, 3655.
lower DGa (Table 2).
inv
In conclusion, this investigation provided a simple synthetic
approach for generating (substituted) buckybowls 2 from 9,10-
diarylphenanthrenes 3 in the solution phase. The protocol
provides several advantages over the FVP route. The method
is now being extended to the construction of other bowl-
shaped molecules and studies of their physical properties are
in progress.
11 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone,
B. Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li,
H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng,
J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda,
J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao,
H. Nakai, T. Vreven, J. A. Montgomery, Jr., J. E. Peralta,
F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin,
V. N. Staroverov, R. Kobayashi, J. Normand, K. Raghavachari,
A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi,
N. Rega, J. M. Millam, M. Klene, J. E. Knox, J. B. Cross,
V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts,
R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi,
C. Pomelli, J. Ochterski, R. L. Martin, K. Morokuma,
V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J. Dannenberg,
S. Dapprich, A. D. Daniels, O. Farkas, J. B. Foresman, J. V. Ortiz,
J. Cioslowski and D. J. Fox, GAUSSIAN 09 (Revision A.1),
Gaussian, Inc., Wallingford, CT, 2009.
Notes and references
1 Reviews for molecular bowls: (a) Y. T. Wu and J. S. Siegel, Chem.
Rev., 2006, 106, 4843; (b) V. M. Tsefrikas and L. T. Scott, Chem.
Rev., 2006, 106, 4868; (c) A. Sygula and P. W. Rabideau, in Carbon-
Rich Compounds: From Molecules to Materials, ed. M. Haley and
R. Tykwinski, Wiley-VCH, Weinheim, 2006, pp. 529; (d) A. Hirsch,
Top. Curr. Chem., 1999, 199, 1; (e) L. T. Scott, Pure Appl. Chem.,
1996, 68, 291; (f) P. W. Rabideau and A. Sygula, Acc. Chem. Res.,
1996, 29, 235; (g) H. Terrones and A. L. Mackay, in The Fullerenes,
ed. H. W. Kroto, J. E. Fischer and D. E. Cox, Pergamon, Oxford,
1993, pp. 113; (h) T. J. Seiders and J. S. Siegel, Chem. Britain, 1995,
31, 307.
2 (a) E. Clar, The Aromatic Sextet, John Wiley and Sons, London,
1972; (b) E. Clar, Polycyclic Hydrocarbons, Academic Press,
London, 1964, vol. 1 and 2.
3 H. E. Bronstein and L. T. Scott, J. Org. Chem., 2008, 73, 88.
4 (a) H. E. Bronstein, N. Choi and L. T. Scott, J. Am. Chem. Soc.,
2002, 124, 8870. Buckybowl 3-H could also be synthesized in 0.6%
yield from 7,14-dioxo-7,14-dihydrophenanthro[1,10,9,8-opqra]
perylene under thermal conditions (980 1C), see: (b) S. Hagen,
U. Nuechter, M. Nuechter and G. Zimmermann, Polycyclic
Aromat. Compd., 1995, 4, 209.
12 Variable temperature 1H-NMR study of suitably-substituted
corannulenes, see: (a) A. Sygula, A. H. Abdourazak and
P. W. Rabideau, J. Am. Chem. Soc., 1996, 118, 339;
(b) L. T. Scott, M. M. Hashemi and M. S. Bratcher, J. Am. Chem.
Soc., 1992, 114, 1920. The computational value of DGa for the
inv
non-substituted corannulene, see: (c) T. J. Seiders, K. K. Baldridge,
G. H. Grube and J. S. Siegel, J. Am. Chem. Soc., 2001, 123, 517;
(d) T. J. Seiders, K. K. Baldridge, E. L. Elliott, G. H. Grube and
J. S. Siegel, J. Am. Chem. Soc., 1999, 121, 7439.
13 H. Sakurai, T. Daiko and T. Hirao, Science, 2003, 301, 1878.
14 (a) R. C. Haddon and L. T. Scott, Pure Appl. Chem., 1986, 58, 137;
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15 The X-ray structure of corannulene: (a) M. A. Petrukhina,
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70, 5713; (b) J. C. Hanson and C. E. Nordman, Acta Crystallogr.,
Sect. B: Struct. Crystallogr. Cryst. Chem., 1976, 32, 1147.
16 The X-ray structure of sumanene: H. Sakurai, T. Daiko,
H. Sakane, T. Amaya and T. Hirao, J. Am. Chem. Soc., 2005,
127, 11580.
5 H. A. Reisch, M. S. Bratcher and L. T. Scott, Org. Lett., 2000, 2, 1427.
6 Several buckybowls have been synthesized by palladium-catalyzed
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c
This journal is The Royal Society of Chemistry 2010
Chem. Commun., 2010, 46, 7241–7243 7243