Synthesis of aromatic compounds by catalytic C-C bond activation of biphenylene or angular [3]phenylene

Article abstract of DOI:10.1002/chem.201103888

Substituted phenanthrenes and picenes were easily prepared by reaction of biphenylene or angular [3]phenylene with various alkynes in the presence of a catalytic amount of [IrCl(cod)]₂/dppe (cod=1,5-cyclooctadiene, dppe=1,2-bis(diphenylphosphin

Full text of DOI:10.1002/chem.201103888

DOI: 10.1002/chem.201103888
À
Synthesis of Aromatic Compounds by Catalytic C C Bond Activation of
Biphenylene or Angular [3]Phenylene
Alesˇ Korotvicˇka,[a] Ivana Cꢀsarˇovꢁ,[b] Jana Roithovꢁ,*[a] and Martin Kotora*[a, c]
4200
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2012, 18, 4200 – 4207

FULL PAPER
Abstract: Substituted phenanthrenes and picenes were easily prepared by reaction
of biphenylene or angular [3]phenylene with various alkynes in the presence of
a catalytic amount of [IrClACTHNUTRGENUG(N cod)]2/dppe (cod=1,5-cyclooctadiene, dppe=1,2-bis(di-
Keywords: arenes · cleavage reac-
tions · iridium · reaction mecha-
nisms · rhodium
À
phenylphosphino)ethane). The reaction is based on C C bond activation of the cy-
clobutane ring. The reaction tolerates the presence of bulky groups on the alkyne,
such as the ferrocene moiety. In addition, a catalytic system based on [RhCl-
ACHTUNGTRENNUNG
Introduction
Results and Discussion
À
Synthesis of aromatic compounds that possess extended p-
conjugated systems is of considerable interest because of
their potential use in organic electronic materials.[1] Substan-
ces that contain the phenanthrene motif belong in this class
of compounds. As a typical example, picene has recently
been shown to exhibit superconducting properties.[2] Al-
though there are a number of synthetic procedures that
could be used for the preparation of phenanthrenes,[3] pi-
cenes,[4] and their extended aromatic and heteroaromatic
congeners,[5] the development of new, selective, and efficient
procedures is highly desirable. Especially, the use of synthet-
We were interested whether C C bond activation of 1 could
be carried out simply by using commercially available li-
gands and if the subsequent reaction with various carbon–
carbon (alkynes) and carbon–nitrogen (nitriles) triple bonds
was achievable. Further attention was focused on the inser-
tion of sterically hindered alkynes that bore a ferrocene
moiety. To this end, we screened the reaction of 1 with 1-
phenylpropyne (2a) in the presence of a catalytic amount of
[IrClACTHUNTRGEN(NUG cod)]2 (10 mol%, cod=1,5-cyclooctadiene) and vari-
ous mono- (PPh3) and bidentate ligands (1,1-bis(diphenyl-
phosphino)methane (dppm), 1,2-bis(diphenylphosphino)-
ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp),
and 1,4-bis(diphenylphosphino)butane (dppb)). From nu-
merous experiments, dppe emerged as the most suitable
ligand. In the presence of dppe, 9-phenyl-10-methylphenan-
threne (3a) was obtained in 83% isolated yield (Table 1,
À
ic methodologies based on catalytic C C bond activation
followed by annulation reactions with unsaturated substrates
is synthetically attractive. Potentially suitable starting mate-
rials are biphenylene (1), which contains a strained cyclobu-
tane ring, and its higher congeners, the polyphenylenes.[6]
Although a number of transition-metal complexes have
been reported to undergo oxidative addition to the bi-
Table 1. Reaction of 1 with 2.
[7]
À
phenyl
N
only a handful of reports has dealt with the subsequent reac-
tion with alkynes to result in the formation of a new aromat-
ic ring.[7e,8,9] In this report, we present new conditions for
the reaction of the strained cyclobutadiene rings of bi- and
polyphenylenes with alkynes or nitriles to give aromatic
compounds.
Entry
Alkyne
Product
Yield
[%][a]
1
2
3
2a
2b
2c
3a
3b
3c
92 (83)
–
[b] (47)
75 (57)
ˇ
[a] A. Korotvicka, Prof. J. Roithovꢁ, Prof. M. Kotora
Department of Organic and Nuclear Chemistry
Faculty of Science, Charles University in Prague
Hlavova 8, 128 43 Praha 2 (Czech Republic)
Fax : (+420)9-221951326
4
5
2d
2e
3d
3e
40 (11)
99 (80)
E-mail: roithova@natur.cuni.cz
6
2 f
2g
2h
3 f
3g
3h
–
[b] (53)
kotora@natur.cuni.cz
ˇ
[b] Dr. I. Cꢂsarovꢁ
Department of Inorganic Chemistry
Faculty of Science, Charles University in Prague
Hlavova 8, 128 43 Praha 2 (Czech Republic)
7
58 (51)
52 (42)
[c] Prof. M. Kotora
8[c]
Institute of Organic Chemistry and Biochemistry, v.v.i.
Academy of Sciences of the Czech Republic
Flemingovo nꢁm. 2
1
[a] Determined by H NMR spectroscopy, isolated yields are in parenthe-
ses. [b] Signals of the internal standard were covered by signals of the
products, which disabled determination of the yield by H NMR spectros-
166 10 Praha 6 (Czech Republic)
1
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201103888.
copy. [c] The reaction was carried out in m-xylene at 1608C.
Chem. Eur. J. 2012, 18, 4200 – 4207
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4201

M. Kotora, J. Roithovꢁ et al.
entry 1). The reaction did not proceed with the bidentate li-
gands dppm, dppp, or dppb. In the presence of monodentate
ligand PPh3 (20 mol%), 3a was formed in 39% yield. Inter-
estingly, when 2a was used in four-fold excess with respect
to 1, the yield of 3a dropped to 28%. The reaction with di-
phenylacetylene (2b) yielded 3b in 47% isolated yield
(Table 1, entry 2). The reaction with diACTHNUTRGNEUNG(p-tolyl)acetylene
(2c) gave the best yield of 3c (NMR spectroscopy: 75%;
isolated: 57%) when two equivalents of alkyne were used
(Table 1, entry 3). When one equivalent of 2c was used
a 47% isolated yield was obtained. In the case of di(p-car-
bomethoxyphenyl)acetylene (2d) the reaction proceeded
well to form 3d in reasonable yield (NMR spectroscopy:
40%; isolated: 11%). Problems associated with the isolation
of 3d in an analytically pure form were responsible for the
poor isolated yield (Table 1, entry 4). Unlike aryl-substituted
alkynes, four equivalents of 4-octyne (2e) were required to
obtain a high isolated yield of dipropylphenanthrene (3e,
80%, Table 1, entry 5). When 1.5, 2, or 3 equivalents of
alkyne were used 3e was formed in 27, 31, and 96% yield
(by NMR spectroscopy), respectively.
Figure 1. X-ray structure of 3g.
We turned out our attention to sterically hindered alkynes
substituted with a ferrocenyl moiety. Ferrocenyl alkynes are,
due to the steric bulk exerted by the ferrocene group, inter-
esting reaction partners for cycloaddition with other unsatu-
rated compounds. In addition, cycloaddition reactions could
be a suitable methodology for incorporation of the electro-
chemically active ferrocene moiety into more complex mo-
lecular systems. Although ferrocenyl alkynes are readily
available, there is only a handful of papers that deal with
their application in transition-metal-catalyzed cyclotrimeri-
zations.[10] The reaction with propynylferrocene (2 f, 1 equiv)
proceeded to give 9-methyl-10-ferrocenylphenanthrene (3 f)
in 53% isolated yield (Table 1, entry 6). Adjustment of the
alkyne/1 ratio did not lead to any improvement in yield.
Moreover, once again, problems with efficient separation of
the product from the starting material were encountered.
Gratifyingly, the reaction with 1-ferrocenyl-2-(4-carbo-
Figure 2. X-ray structure of 3h.
Interestingly, the reactions with alkynes that bore electron-
withdrawing (such as dimethylacetylene dicarboxylate
(DMAC) and methyl propynoate) or electron-donating
groups (such 1-[(triisopropyl)silyloxy]octyne) did not pro-
ceed. Also, the reaction with di-O-toluoyl-1-(propyn-1-yl)-
deoxyribose[13] did not provide the expected products.
The successful synthesis of phenanthrenes 3 prompted us
to study the, hitherto unreported, reaction of 1 with nitriles
4 to give phenanthridines 5. The Ir-based catalytic system
reported above did not bring about the desired reaction
with 4, but substitution of the iridium complex for [RhCl-
ACHTUNGTRENNUNGmethoxyphenyl)acetylene (2g, 1 equiv) gave rise to 3g in
good isolated yield (51%, Table 1, entry 7). The structure of
3g was unequivocally confirmed by a single-crystal X-ray
analysis (Figure 1). The reaction also proceeded surprisingly
well with diferrocenylacetylene (2h, 1 equiv)[11] to give 9,10-
diferrocenylphenanthrene (3h) in a good isolated yield
(42%, Table 1, entry 8), although the reaction had to be per-
formed in m-xylene at 1608C. It should be emphasized that
this is the first example of a cycloaddition reaction with ster-
ically hindered ferrocenyl alkyne 2h.[12]
The structure of 3h was unequivocally confirmed by
a single-crystal X-ray analysis (Figure 2). Currently, it is not
clear why successful reaction requires a substrate-dependent
alkyne/1 ratio, which varies from 1:1 to 4:1. Possibly, it
could be related to subtle changes in the intrinsic reactivity
of the triple bond induced by electronic and steric effects.
With regards to the scope of the reaction with respect to
the alkyne, the reaction proceeded only with internal al-
kynes, but alkyl or aryl group substitution was acceptable.
AHCTUNGTERG(NNUN cod)]2 in combination with dppe yielded the expected prod-
ucts 5 (Table 2, conditions A). The successful course of the
reaction required an increased catalyst loading (20 mol%)
and reaction temperature (190–2008C) and use of the appro-
priate nitrile as a solvent. The reaction with acetonitrile
(4a) gave phenanthridine 5a in 26% isolated yield (Table 2,
entry 1). The use of benzonitrile (4b) led to phenanthridine
5b in reasonable yield (46%, Table 2, entry 2). Reaction of
1 with benzonitriles 4c or 4d, which bear Cl or CF3 elec-
tron-withdrawing groups, yielded phenanthridines 5c and 5d
in reasonable isolated yields of 57 and 39%, respectively
4202
www.chemeurj.org
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2012, 18, 4200 – 4207

À
Synthesis of Aromatic Compounds by C C Bond Activation
FULL PAPER
Table 2. Reaction of 1 with 4.
Entry Nitrile
Product Conditions A Conditions B
Yield [%][a]
26
Yield [%][a]
1
2
4a
4b
5a
5b
40
Scheme 1. Reaction of 6 with alkynes 2.
46 (50)[b]
92[b]
3
4
5
4c
4d
4e
5c
5d
5e
57
39
80
40
78
25[b]
1
[a] Isolated yield; the yield obtained by H NMR spectroscopy is given in
parentheses. [b] The reaction was carried out at 1808C, 18 h.
(Table 2, entries 3 and 4). Gratifyingly, the reaction with 2-
cyanopyridine (4e) proceeded quantitatively and gave phen-
anthridine 5e in 80% isolated yield (Table 2, entry 5). Next,
we tried to reduce the amount of the catalyst required.
After some experimentation, we discovered that the cationic
complex [RhACHTUNGTRENNUNG(cod)2BF4] (10 mol%) and dppe (10 mol%)
Figure 3. X-ray structure of 7b.
under microwave (MW) irradiation could bring about the
transformation of 1 to phenanthridines 5 with better effi-
ciency in most cases (Table 2, conditions B). Phenanthri-
dines 5a, 5b, and 5d were obtained in 40, 92, 78% isolated
yields, respectively. Phenanthridine 5c was obtained in a sim-
ilar isolated yield (40%); only 5e was obtained in a substan-
tially lower isolated yield of 25%.
rivative 7c was isolated in 13% yield. Although the yields
of the substituted picenes 7 may seem low, these are yields
of the analytically pure compounds. Conversions of 6 were
about 50% (25–30% starting material was recovered) and
we encountered difficulties in separation of the desired
products from byproducts. Interestingly, we did not detect
products of monoinsertion in the reaction mixtures. The re-
action with 2h was also attempted, however, the successful
course of the reaction required the use of m-xylene as a sol-
vent and a higher reaction temperature (1608C). Moreover,
only compound 8—the product of monoinsertion—was ob-
tained, in 25% isolated yield (Scheme 2). Because the oxi-
After screening the reactions of 1 with various alkynes
and establishing suitable reaction conditions, we set out to
attempt a similar process with angular tetrakis(trimethyl-
ACHTUNGTRENNUNG
silyl)-[3]phenylene 6.[14] We presumed that two consecutive
À
C C bonds activations followed by reaction with an alkyne
2 could open a new pathway for the synthesis of 5,6,7,8-sub-
stituted picenes 7.
Although it was reported that [CoACTHUNRGTNEG{UN (CH2=CH2)2}Cp] (Cp=
cyclopentadienyl) reacted with angular [3]phenylene to yield
a bis-cobalt complex,[15] its subsequent reactions with other
substrates have been not been reported as yet. However,
very recently, Vollhardt et al. have reported a Ni-catalyzed
reaction of polyphenylenes with alkynes.[6] We assumed that
a similar intermediate could also form upon reaction with
the iridium catalytic system and could further react with al-
kynes. To this end, angular [3]phenylene 6 was heated in the
Ir-catalyzed reaction with symmetrically substituted alkynes
(Scheme 1). The reaction of 6 with 2e yielded only a small
amount (8%) of the picene derivative 7a. A much better
result was obtained in the reaction with 2b, which gave
picene 7b as the sole product in 27% isolated yield. A
single-crystal X-ray analysis unequivocally confirmed the
structure of the picene framework (Figure 3). A similar
result was also observed in the reaction with 2c; picene de-
Scheme 2. Reaction of 6 with diferrocenylacetylene (2h).
dative addition proceeded from the more hindered edge of
6, it is presumed that further oxidative addition of the cata-
lyst to the remaining cyclobutane ring in 8 is prevented by
the steric hindrance caused by the bulky ferrocene moieties.
Unlike in the Ni-catalyzed reaction, we did not observe
the addition products formed by cleavage of the outer-rim
Chem. Eur. J. 2012, 18, 4200 – 4207
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4203

M. Kotora, J. Roithovꢁ et al.
À
region of the C C bonds. Instead, the reaction catalyzed by
the investigated system and calculate the whole potential-
energy surface. We opted to calculate the relative stabilities
of iridium-containing intermediates, which are formed by
the opening of a four-membered ring from the inner or
outer rim of 6 (or 11/12 in the second step), to determine
the formation of the given product isomers (Table 4 and
Scheme 4).
the iridium(I) complex proceeded exclusively to form
picene derivatives 7. Hence, we were interested in the origin
of this selectivity. Exploratory DFT calculations revealed
that the inclusion of dispersion interactions is indispensable
for the correct description of the products. For example, the
relative energies of picenes 7, benzo[c]chrysenes 9, and heli-
cenes 10 (R1 =R2 =H, Scheme 3) calculated at the B3LYP
Table 4. Relative energies [kJmolÀ1] of iridacycle intermediates calculat-
ed at the MP2//B3LYP level.[a]
Intermediate
R=H
R=TMS
6_in
0.0
12.7
0.0
65.3
À13.1
69.4
N
0.0
12.7
0.0
65.3
À13.1
69.4
ACHTUNGTRENNUNG
6_out
11_in
11_out
12_in
12_out
G
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
R
ACHTUNGTRENNUNG
N
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
[a] Energies are given at 0 K and the values in parentheses refer to the
relative Gibbs energies at 298 K.
Scheme 3. Possible products of the reaction of 6 with 2b under iridium
catalysis.
The reaction proceeded in nonpolar solvent, therefore,
only neutral forms of the intermediates with the active form
of the catalyst [IrClACTHNGUTERN(UNG dppe)] were considered. Opening of the
level are 0, 28, and 52 kJmolÀ1, respectively (Table 3). By
comparison, the empirical correction of the dispersion inter-
action at the B97D level leads to the values 0, 23, and
38 kJmolÀ1, respectively. Single-point calculations at the
MP2 level (for the B3LYP optimized structures) lead to
very similar values (0, 22, and 33 kJmolÀ1, respectively). The
energy differences for the derivatives with trimethylsilyl
(TMS) and phenyl substituents are even larger (Table 3).
Hence, it can be concluded that if dispersion interactions
are neglected, the relative stabilities of these aromatic sys-
tems substantially change. As the empirical corrections of
dispersion interactions are not available for iridium, in the
following study we decided to optimize the structure at the
B3LYP level and correct of the energy by a single-point cal-
culation at the MP2 level.
Although 7 is thermodynamically favored over isomers 9
and 10, the introduction of phenyl substituents leads to an
inversion of the thermodynamic stability. The most stable
isomer corresponds to the backbone 10, followed by the de-
rivative 9, and the isomer highest in energy is derived from
7. Hence, we observed exclusive formation of the thermody-
namically disfavored product. The course of the reaction is
influenced by the interplay between steric, dispersion, and
coordination effects, therefore we cannot reduce the size of
four-membered ring of 6 from the inner-rim side leads to
the iridiacycle intermediate 6_in, whereas ring opening from
the outer rim leads to the 6_out intermediate (Scheme 4).
The formation of the 6_out intermediate is disfavored by
more than 10 kJmolÀ1; this effect is even more pronounced
in the presence of TMS substituents (R=TMS; Table 4).
The reactions of 6_in and 6_out with 2b lead to the forma-
tion of 11 and 12, respectively. Based on the stabilities of
the iridiacycle intermediates, a preference for the formation
of 11 is expected and, additionally, the TMS groups contrib-
ute to a larger selectivity of the reaction.
The opening of the four-membered ring of 11 can also
proceed from the inner- or outer-rim side. Opening from the
inner-rim side leads to the intermediate 11_in (Scheme 4)
and is thermodynamically favored relative to opening from
the outer-rim side by about 60 kJmolÀ1 (Table 4). The reac-
tion of intermediate 11_in with 2b leads to the formation of
isomer 7 and, thus, explains the exclusive observation of this
product in the iridium-catalyzed reaction. For completeness,
we have also followed the opening of the four-membered
ring of 12. Similarly to the reaction of 11, opening from the
inner-rim side is more favored by about 60 kJmolÀ1 and,
therefore, the overall reaction pathway via 12 would yield
the isomer 9.
The results suggest that the first reaction step,
which gives intermediates 11 or 12, is the selectivi-
ty-determining step. For the reactants that do not
bear TMS groups a minor formation of the inter-
mediate product 12 formed by outer-rim opening
could be observed. The TMS-substituted reactants
were investigated and the reaction proceeds exclu-
sively to form 11. The second step proceeds selec-
tively due to the large energy preference for attack
Table 3. Comparison of the energies[a] [kJmolÀ1] of 9 and 10 relative to the energy of
7 (0 kJmolÀ1) calculated at different levels of theory.
Benzo[c]chrysenes 9
Helicenes 10
B3LYP B97D MP2//B3LYP B3LYP B97D MP2//B3LYP
R1 =R2 =H[b]
28
27
23
19
À11
22
22
À9
52
53
À29
38
12
À24
33
11
À21
R1 =TMS, R2 =H[b]
R1 =TMS, R2 =Ph[c] À16
[a] Energies at 0 K. [b] Basis set p-VTZ. [c] Basis set p-VDZ.
4204
www.chemeurj.org
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2012, 18, 4200 – 4207

À
Synthesis of Aromatic Compounds by C C Bond Activation
FULL PAPER
Conclusion
We have demonstrated that a simple [IrClACTHNURTGNENG(U cod)]2/dppe-
based catalytic system is suitable for reaction of 1 with vari-
ous alkynes 2 to give 9,10-substituted phenanthrenes 3.
Moreover, this methodology was extended to angular
[3]phenylene, which outlines a new pathway for the prepara-
tion of 5,6,7,8-substituted picene derivatives 7. In a similar
manner, a [RhClACHTNUTRGNEUNG(cod)]2/dppe catalytic system is convenient
for the, hitherto unreported, reactions of 1 with nitriles 4 to
produce substituted phenanthridines 5. Exploratory calcula-
tions, based on the investigation of the relative stabilities of
the iridiacycle intermediates, suggest that opening of the
four-membered ring of 6 from the inner-rim region is fa-
vored relative to opening from the outer-rim region. The se-
lectivity of the reaction is enhanced by the TMS substitution
of the reactants. These results explain the exclusive observa-
tion of the picene derivatives 7.
Experimental Section
General procedure for alkyne insertion into biphenylene: Under Ar,
[IrClACHTNURGTNE(UGN cod)2]2 (13.4 mg, 0.02 mmol) and dppe (15.9 mg, 0.04 mmol) were
added to a vial equipped with a septum. Toluene (1.5 mL) or m-xylene
(1.5 mL) was added by syringe and the mixture was stirred until dissolu-
tion was achieved (ꢀ5 min). Compound
1 (30.4 mg, 0.2 mmol) and
alkyne 2 (0.2–0.8 mmol) were added and the reaction mixture was heated
in an oil bath for 3.5–6.5 h. The volatile compounds were removed under
reduced pressure and purification of the residue by column chromatogra-
phy on silica gel yielded 3.
Compound 3 f: Compound 1 (30.4 mg, 0.2 mmol), 2 f (45 mg, 0.2 mmol),
1308C, 4 h. Column chromatography (5:1 hexane/CH2Cl2) yielded 3 f as
an orange solid (40 mg, 53%). Rf (5:1 hexane/CH2Cl2)=0.48; m.p.
1618C; 1H NMR (300 MHz, C6D6): d=2.69 (s, 3H), 4.01 (s, 5H), 4.18
(apparent t, 2H), 4.35 (apparent t, 2H), 7.43–7.51 (m, 4H), 7.94–8.00 (m,
1H), 8.54–8.62 (m, 2H), 9.50 ppm (d, J=7.5 Hz, 1H); 13C NMR
(75 MHz, CDCl3): d=19.23, 67.31 (2C), 69.71 (5C), 72.96 (2C), 86.02,
122.37, 122.65, 124.95, 125.05, 125.39, 125.95, 126.74, 127.92, 129.46,
129.69, 131.04, 131.80, 131.93, 132.45 ppm; IR (KBr): n˜ =503, 720, 746,
826, 999, 1105, 1442, 1491 cmÀ1; MS (ES+): m/z (%): 376 (100) [M]+, 171
(3); HRMS: m/z calcd for C25H20Fe: 376.0909; found: 376.0908.
Scheme 4. B3LYP/cc-pVDZ:LANL2DZ calculated structures of possible
intermediates in the reaction of 6 with the iridium catalyst. R=H or
TMS. Notation 6_in stands for the intermediate formed by the opening
of a four-membered ring of a compound 6 from the inner rim, all other
intermediates are denoted analogously. The aromatic part of the synthe-
sized skeleton is depicted in yellow and the phenyl rings of the dppe
ligand are grey.
General procedure for nitrile insertion: Under Ar, [RhCl
ACHTUNGTRENNUNG(cod)2]2
(19.8 mg, 0.04 mmol), dppe (31.8 mg, 0.08 mmol), and (30.4 mg,
1
0.2 mmol) were added to a vial equipped with a septum. Nitrile 4
(1.5 mL) was added (solid nitriles (2.0 mmol) were dissolved in THF
(1 mL) before addition). The reaction mixture was heated in an oil bath
or in a MW reactor. Excess of 4 was removed under reduced pressure
(oil pump, 1008C). Column chromatography of the residue on silica gel
yielded 5.
of the inner-rim of intermediates 11 or 12, which explains
why only derivatives of 7 were observed.
Compound 5c: Compound 4c (1.5 mL), oil bath, 1908C, 4 h. Column
chromatography (5:1 hexane/EtOAc) yielded 5c (41 mg, 80%) as a color-
less solid. Rf (5:1 hexane/EtOAc)=0.2; 1H NMR (300 MHz, CDCl3): d=
7.43 (ddd, J=7.5, 5.1, 1.5 Hz, 1H), 7.62–7.96 (m, 5H), 8.03 (d, J=8.1 Hz,
1H), 8.26 (d, J=7.8 Hz, 1 Hz), 8.50 (d, J=8.4 Hz, 1H), 8.62 (dd, J=8.1,
1.5 Hz, 1H), 8.69 (d, J=8.4 Hz, 1H), 8.81 ppm (d, J=4.8 Hz, 1H);
13C NMR (75 MHz, CDCl3): d=121.97, 122.01, 123.34, 124.18, 124.72,
125.15, 127.30 (2C), 128.70, 128.86, 130.41, 130.55, 133.59, 137.02, 143.52,
148.68, 158.32 ppm (2C). Spectral characteristics were in agreement with
the published data.[16]
The fact that the reaction proceeds towards the thermody-
namically disfavored products (the derivative 7 is more than
20 kJmolÀ1 higher in energy than 10 and about 10 kJmolÀ1
higher in energy than 9) is most probably determined by the
relative stabilities of the iridacycle intermediates. Therefore,
the reaction course could also depend crucially on ligands
and other features of the transition-metal catalyst. This and
other aspects of the reaction will be subject of future stud-
ies.
General procedure for picene synthesis: Under Ar, [IrClACHTUNGTRENNUNG(cod)2]2
(13.4 mg, 0.02 mmol) and dppe (15.9 mg, 0.04 mmol) were added to a vial
equipped with a septum. Toluene (1 mL) was added by syringe and the
Chem. Eur. J. 2012, 18, 4200 – 4207
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4205

M. Kotora, J. Roithovꢁ et al.
mixture was stirred until dissolved (5 min). Compound
6
(51.4 mg,
[6] Y. Hu, G. B. Boursalian, V. Gandon, R. Padilla, H. Shen, T. V. Timo-
feeva, P. Tongwa, K. P. C. Vollhardt, A. A. Yakovenko, Angew.
Chem. 2011, 123, 9585–9589; Angew. Chem. Int. Ed. 2011, 50, 9413–
9417.
0.1 mmol) and alkyne 2 (2–8 equiv) were added and the reaction mixture
was heated in an oil bath at 1308C for 5 h. The volatile compounds were
removed under reduced pressure and column chromatography of the res-
idue, followed by preparative TLC or crystallization, yielded 7.
[7] For various transition metals, see: a) C. Perthuisot, B. L. Edelbach,
D. L. Zubris, N. Simhai, C. N. Iverson, C. Mꢅller, T. Satoh, W. D.
Jones, J. Mol. Catal. A 2002, 189, 157–168; for Ni, see: b) J. Eisch,
A. M. Piotrowski, K. I. Han, C. Krꢅger, Y. H. Tsay, Organometallics
1985, 4, 224–231; c) H. Schwager, S. Spyroudis, K. P. C. Vollhardt, J.
Organomet. Chem. 1990, 382, 191–200; d) T. Schaub, U. Radius,
Chem. Eur. J. 2005, 11, 5024–5030; e) T. Schaub, M. Backes, U.
Radius, Organometallics 2006, 25, 4196–4206; for Ir, see:f) Z. Lu,
C.-H. Jun, S. R. Gala, M. P. Sigalas, O. Eisenstein, R. H. Crabtree, J.
Chem. Soc. Chem. Commun. 1993, 1877–1880; g) Z. Lu, C.-H. Jun,
S. R. Gala, M. P. Sigalas, O. Eisenstein, R. H. Crabtree, Organome-
tallics 1995, 14, 1168–1175; for Pt, see: h) B. L. Edelbach, R. J. La-
chicotte, W. D. Jones, J. Am. Chem. Soc. 1998, 120, 2843–2853; for
Fe, see: i) W.-Y. Yeh, S. C. N. Hsu, S.-M. Peng; G.-H. Lee, Organo-
metallics 1998, 17, 2477–2483; G.-H. Lee, Organometallics 1998, 17,
2477–2483; for Pd, see: j) K. Yu, H. Li, E. J. Watson, K. L. Virkaitis,
G. B. Carpenter, D. A. Sweigart, Organometallics 2001, 20, 3550–
3559; for Co, see: k) C. Perthuisot, B. L. Edelbach, D. L. Zubris,
W. D. Jones, Organometallics 1997, 16, 2016–2023.
Compound 7b: Compound
6 (44 mg, 0.086 mmol), 2b (30.1 mg,
0.17 mmol), 4 h. Filtration through a short pad of silica gel (CH2Cl2),
column chromatography (20:1, then 10:1 hexane/CH2Cl2) yielded 7b
(20 mg, 27%) as a yellowish solid. Rf (10:1 hexane/CH2Cl2)=0.32; m.p.
3138C; 1H NMR (300 MHz, CDCl3): d=0.21 (s, 18H), 0.57 (s, 18H),
6.00–6.19 (m, 6H), 6.55–6.70 (m. 4H), 6.86–6.92 (m, 2H), 6.92–7.00 (ap-
parent t, J=7.8, 7.8, 0.9 Hz, 2H), 7.16–7.23 (m, 2H), 7.32–7.45 (m, 4H),
7.78 (s, 2H), 8.97 (s, 2H), 9.19 ppm (s, 2H); 13C NMR (150 MHz, CDCl3):
d=1.63 (3C), 2.06 (3C), 121.13, 125.45, 125.64 (2C), 126.19, 126.80,
127.75, 128.22, 129.52, 129.83, 130.42, 130.56, 131.25, 132.27, 133.40 (2C),
135.32, 136.86, 138.18, 139.88, 140.35, 142.71, 142.93 ppm; IR (KBr): n˜ =
2953, 1440, 1250, 1122, 853, 839, 757, 699 cmÀ1; MS (ES+): m/z (%): 894
(80) [M+Na]+, 893 (100), 822 (14), 821 (19), 783 (10), 390 (4); HRMS:
m/z calcd for C58H62Si4: 871.3977; found: 871.3986.
The computational DFT study was performed by using the B3LYP[17–20]
functional as implemented in the Gaussian 09 package.[21] Basis sets cc-
VTZ or cc-VDZ for molecules without iridium (explicitly denoted in
Table 3) and a combination of LAN2DZ for iridium and cc-VDZ for the
remaining atoms of the iridium-containing intermediates (denoted as
LAN2DZ:cc-pVDZ) were used.[22,23] Frequency analysis was performed
for all optimized structures to assure that they corresponded to the
minima on the potential-energy surface and to calculate the zero-point
energy. The MP2 single-point calculations were performed for the opti-
mized geometries. The zero-point energy and Gibbs energy corrections
were calculated at the B3LYP level and added to the MP2 energies. All
energies given in the paper refer to 0 and 298 K. The test calculations on
the effect of the dispersion interactions were made at the levels of theory
B3LYP/cc-pVTZ, B97D/cc-pVTZ,[24] and MP2/cc-pVTZ//B3LYP/cc-
pVTZ. Note that the use of B3LYP energies alone lead to different
mechanistic predictions. The B3LYP level does not cover the dispersion
interactions, which however play an important role in the studied reac-
tion. Therefore, the B3LYP energies cannot be considered as correct.
[8] a) B. L. Edelbach, R. J. Lachicotte, W. D. Jones, Organometallics
1999, 18, 4040–4049; b) B. L. Edelbach, R. J. Lachicotte, W. D.
Jones, Organometallics 1999, 18, 4660–4668; c) C. N. Iverson, W. D.
Jones, Organometallics 2001, 20, 5745–5750.
[9] T. Shibata, G. Nishizawa, K. Endo, Synlett 2008, 765–768.
[10] Cyclotrimerization of ferrocenyl alkynes: a) K. Schlçgl, H. Soukup,
Tetrahedron Lett. 1967, 8, 1181–1184; b) M. Rosenblum, N. Brawn,
ˇ
ˇ
ˇ
B. King, Tetrahedron Lett. 1967, 8, 4421–4424; c) P. Stepnicka, I.
ˇ
ˇ
ˇ
Cꢂsarovꢁ, J. Sedlꢁcek, J. Vohlꢂdal, M. Polꢁsek, Collect. Czech. Chem.
ˇ
ˇ
Commun. 1997, 62, 1577–1584; d) L. Dufkovꢁ, I. Cꢂsarovꢁ, P. Step-
ˇ
nicka, M. Kotora, Eur. J. Org. Chem. 2003, 2882–2887; e) L
ˇ
ˇ
ˇ
ˇ
Dufkovꢁ, H. Matsumura, D. Necas, P. Stepnicka, F. Uhlꢂk, M.
Kotora, Collect. Czech. Chem. Commun. 2004, 69, 351–364.
ˇ
ˇ
ˇ
ˇ
[11] D. Necas, M. Kotora, P. Stepnicka, Collect. Czech. Chem. Commun.
2003, 68, 1897–1903.
CCDC-835379 (3h), CCDC-835380 (7b), and CCDC-835381 (3g) contain
the supplementary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
[12] Our previous attempts to carry out catalytic homocyclotrimerization
of 2h in the presence of Rh, Ru, or Ni-catalysts did not yield any
product. Also co-cyclotrimerization with various 1,7-hepta- and 1,8-
octadiynes did not give the expected products and only homocyclo-
trimerization of the diynes was observed. Hexaferrocenylbenzene
was prepared by Vollhardt et al. by Negishi cross-coupling: Y. Yu,
A. D. Bond, P. W. Leonard, U. J. Lorenz, T. V. Timofeeva, K. P. C.
Vollhardt, G. D. Whitener, A. A. Yakonvenko, Chem. Commun.
2006, 2572–2574.
Acknowledgements
[13] The participation of di-O-toluoyl-1-(propyn-1-yl)deoxyribose in cy-
ˇ
clotrimerization was reported, see: P. Novꢁk, S. Cꢂhalovꢁ, M. Otmar,
The authors acknowledge financial support from the Ministry of Educa-
tion, Youth and Sports of the Czech Republic (grant nos. LC06070 and
MSM0021620857), Charles University in Prague (grant no. SVV 263205/
2011), and the Grant Agency of the Czech Republic (207/11/0338)
M. Hocek, M. Kotora, Tetrahedron 2008, 64, 5200–5207.
[14] D. L. Mohler, S. Kumaraswamy, A. Stanger, K. P. C. Vollhardt, Syn-
lett 2006, 18, 2981–2984.
ˇ
[15] S. Kumaraswamy, S. S. Jalisatgi, A. J. Matzger, O. S. Miljanic, K. P. C.
Vollhardt, Angew. Chem. 2004, 116, 3797–3801; Angew. Chem. Int.
Ed. 2004, 43, 3711–3715.
[16] J. Pawlas, M. Begtrup, Org. Lett. 2002, 4, 2687–2690.
[17] S. H. Vosko, L. Wilk, M. Nusair, Can. J. Phys. 1980, 58, 1200.
[18] C. Lee, W. Yang, R. G. Parr, Phys. Rev. B 1988, 37, 785.
[19] A. D. Becke, Phys. Rev. A 1988, 38, 3098.
[1] Y. Yamashita, Sci. Technol. Adv. Mater. 2009, 10, 024313.
[2] R. Mitsuhashi, Y Suzuki, Y. Yamanari, H. Mitamura, T. Kambe, N.
Ikeda, H. Okamoto, A. Fujiwara, M. Yamaji, N. Kawasaki, Y.
Maniwa, Y. Kubozono, Nature 2010, 464, 76–79.
[3] For recent papers on phenanthrene synthesis, see: a) A. Matsumoto,
L. Ilies, E. Nakamura, J. Am. Chem. Soc. 2011, 133, 6557–6558;
b) C. Wang, S. Rakshit, F. Glorius, J. Am. Chem. Soc. 2010, 132,
14006–14008; c) A. G. Neo, C. Lꢃpez, V. Romero, B. Antelo, J. De-
lamano, A. Pꢄrez, D. Fernꢁndez, J. F. Almeida, L. Castedo, G. Tojo,
J. Org. Chem. 2010, 75, 6764–6770.
[4] a) H. Okamoto, M. Yamaji, S. Gohda, Y. Kubozono, N. Komura, K.
Sato, H. Sugino, K. Satake, Org. Lett. 2011, 13, 2758–2761; b) L.
Wang, P. B. Shevlin, Org. Lett. 2000, 2, 3703–3705.
[5] T.-A. Chen, T.-J. Lee, M.-Y. Lin, S. M. A. Sohel, E. W.-G. Diau, S.-F.
Lush, R.-S. Liu, Chem. Eur. J. 2010, 16, 1826–1833.
[20] A. D. Becke, J. Chem. Phys. 1993, 98, 5648.
[21] Gaussian 09, Revision A.02, M. J. Frisch, G. W. Trucks, H. B. Schle-
gel, 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. Son-
nenberg, 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,
4206
www.chemeurj.org
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2012, 18, 4200 – 4207

À
Synthesis of Aromatic Compounds by C C Bond Activation
FULL PAPER
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. W.
Ochterski, R. L. Martin, K. Morokuma, V. G. Zakrzewski, G. A.
Voth, P. Salvador, J. J. Dannenberg, S. Dapprich, A. D. Daniels, ꢆ.
Farkas, J. B. Foresman, J. V. Ortiz, J. Cioslowski, and D. J. Fox,
Gaussian, Inc., Wallingford CT, 2009.
[22] T. H. Dunning Jr., J. Chem. Phys. 1989, 90, 1007.
[23] P. J. Hay, W. R. Wadt, J. Chem. Phys. 1985, 82, 299.
[24] S. Grimme, J. Comput. Chem. 2006, 27, 1787–1799.
Received: December 12, 2011
Published online: March 12, 2012
Chem. Eur. J. 2012, 18, 4200 – 4207
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4207