Gold-catalyzed synthesis of dibenzopentalenes - Evidence for gold vinylidenes

Article abstract of DOI:10.1002/adsc.201200086

A series of easily accessible arene-1,2-diynes, bearing one aryl substituent on one of the alkynyl groups, is readily converted to dibenzopentalenes in good yields by gold(I) catalysts. The participation of gold acetylides could be proven by the direct conversion to the corresponding gem-diaurated dibenzopentalenes with a gold catalyst. From an experiment with a gold acetylide complex and stoichiometric amounts of the gold "catalyst" the corresponding gem-diaurated complex of a dibenzopentalene could be obtained and characterized by X-ray crystal structure analysis. Labelling studies with deuterated alkynes show the expected deuteration of the two remaining positions of the pentalene core. All this provides evidence for a dual activation mode of the reaction and gold(I) vinylidene complexes as intermediates of the catalytic cycle. Copyright

Full text of DOI:10.1002/adsc.201200086

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DOI: 10.1002/adsc.201200086
Gold-Catalyzed Synthesis of Dibenzopentalenes – Evidence for
Gold Vinylidenes
A. Stephen K. Hashmi,a,* Marcel Wieteck,a Ingo Braun,a Pascal Nçsel,a
Linda Jongbloed,a Matthias Rudolph,a and Frank Romingera,b
a
Organisch-Chemisches Institut, Ruprecht-Karls-Universitꢀt Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg,
Germany
Fax : (+49)-6221-54-4205
(http://www.hashmi.de); e-mail: hashmi@hashmi.de
Crystallographic investigation
b
Received: December 20, 2011; Revised: February 1, 2012; Published online: February 23, 2012
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.201200086.
Abstract: A series of easily accessible arene-1,2-
diynes, bearing one aryl substituent on one of the
alkynyl groups, is readily converted to dibenzopen-
talenes in good yields by gold(I) catalysts. The par-
ticipation of gold acetylides could be proven by the
direct conversion to the corresponding gem-diaurat-
ed dibenzopentalenes with a gold catalyst. From an
experiment with a gold acetylide complex and stoi-
chiometric amounts of the gold “catalyst” the corre-
sponding gem-diaurated complex of a dibenzopenta-
lene could be obtained and characterized by X-ray
crystal structure analysis. Labelling studies with
deuterated alkynes show the expected deuteration
of the two remaining positions of the pentalene
core. All this provides evidence for a dual activa-
tion mode of the reaction and gold(I) vinylidene
complexes as intermediates of the catalytic cycle.
that the participation of gold acetylides can induce
completely different selectivities in gold-catalyzed re-
actions. It also proves a double activation by the gold
catalyst. By using basic additives or organo-gold com-
pounds, the gold acetylide formation could be en-
forced and instead of the expected a-phenylnaphtha-
lenes a-2, we observed the exclusive formation of iso-
meric b-phenylnaphthalene b-2. The results from that
very complex mechanistic study indicate that so far
only scarcely mentioned gold vinylidene species are
involved in the reaction mechanism.[4]
Here we report another exciting aspect of this com-
pletely new type of gold-catalyzed conversion. When
we investigated arene-diynes possessing one terminal
and one aryl-substituted alkyne, completely different
products were obtained. No incorporation of the aro-
Keywords: alkynes; dibenzopentalenes; digold com-
pounds; extended p-systems; gold catalysis; gold vi-
nylidenes; vinylgold intermediates
In the highly active field of homogeneous gold-cata-
lyzed reactions,[1] only recently, have diynes been em-
ployed as starting materials. The general reactivity
pattern of the reactions is based on an initial attack of
an intra- or intermoleculary offered nucleophile onto
one of the triple bonds. The so-formed intermediate
en-yne systems then undergo further transformations
that lead to highly complex molecular structures.[2]
We have just contributed a new hydroarylating aro-
matization of arene-diynes (Scheme 1).[3] This reac-
Scheme 1. Selectivity switch in the hydroarylation–aromati-
tion is mechanistically highly interesting as it proves zation of 1.
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Table 1. Gold-catalyzed dibenzopentalene synthesis.
Entry
1
Substrate
Product
Yield
3a
3b
3c
3d
4a
4b
4c
4d
54%
68%
62%
60%
2
3
4
5
3e
4e
80%
matic solvent into the product was detected. Instead chromatography. Most fortunately, we were able to
the second aromatic system serves as nucleophile collect crystals that were suitable for an X-ray crystal
which allows the fast synthesis of symmetrical and un- structure analysis.[7] Figure 1 shows the solid state
symmetrical dibenzopentalenes. The starting materials structure which unambiguously confirms the dibenzo-
for our substrates were obtained via an efficient two- pentalene architecture. Substitutions at the central ar-
step synthesis from 2-bromobenzaldehydes.[5] Togeth-
er with the new gold-catalyzed protocol this offers an
extremely straightforward access towards this interest-
ing class of molecules which are of interest in the con-
text of materials science (especially for those that are
unsymmetrical).[6]
The results are summarized in Table 1. Simple 1-
ethynyl-2-(phenylethynyl)benzene could be trans-
formed into dibenzopentalene 4a, and only traces of
intermolecular benzene addition products were de-
tected via GC-MS (entry 1). The reason for the only
moderate yield is based on the low solubility of the
resulting product. Thin layer chromatography and in
1
situ H NMR spectroscopy of the reaction indicated
a clean conversion, but a part of the sensitive material
was obviously lost during the purification by column Figure 1. Solid state molecular structure of 4a.
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Gold-Catalyzed Synthesis of Dibenzopentalenes – Evidence for Gold Vinylidenes
Figure 2. Non-reacting substrates.
Scheme 2. Reaction of the thiophene-containing substrate
3h.
omatic system of the starting diynes were also tolerat-
ed (entries 2 and 3) and the yields for the unsymmet-
rical dibenzopentalenes 4b and 4c were also accepta-
Figure 3. Solid state molecular structure of 6.
ble. Next we investigated a differently substituted aro-
matic system at the non-terminal alkyne. While elec-
tron-rich systems delivered selective conversions and
good yields (entries 4 and 5), no conversions were ob- of a single crystal revealed an astonishing dimer of 7
served for the electron-deficient compounds 3f and 3g with an interesting helical distortion (Figure 4).[7]
(Figure 2). A first example for a heterocyclic system Mechanistically, at this moment it remains unclear
could also be obtained (Scheme 2). The thiophene- how this product of an oxidative coupling was
substituted alkyne 3h delivered product 4h, but due formed, but indeed attack of the peri-position of the
to the sensitivity of the product the yield was low.
anthracene moiety onto the intermediate gold vinyli-
In addition to systems with mono-cyclic aromatic dene must have taken place. Then dimerization of the
nucleophiles, we also tested an anthracene moiety in resulting gold species and reduction of the gold might
the substrate (5, Scheme 3). Now the ortho-positions furnish dimer 8.[8]
at the central ring are blocked, but the peri-positions
can serve as nucleophiles. This conversion was very pared mono-acetylide complex 9 and subjected it to
slow, which can be explained by the shielded environ- stochiometric amounts of activated catalyst
ment of the non-terminal alkyne. An unselective reac- (Scheme 4). Interestingly, the formation of a gem-di-
tion was observed, the intermolecular benzene addi- aurated species from the mono-aurated diyne was de-
Next we focussed on mechanistic insights. We pre-
AHCTUNGTRENNUNG
tion pathway was favoured and 24% of b-naphthalene tected. This gem-diaurated compound 10 precipitated
6 could be separated from several ill-defined by-prod- quickly. During purification by recrystallization from
ucts. The certain structural assignment of product 6 benzene/DCM, we were able to obtain single crystals
was possible by an X-ray solid state structure analysis suitable for a X-ray structure analysis.[7] The solid
(Figure 3).[7] In addition to the benzene addition, state structure proves that the two gold atoms are
minute amounts of another crystalline compound positioned at the benzylic carbon of the non-aromatic
were also isolated. An X-ray crystal structure analysis double bond of the dibenzopentalene system
Scheme 3. Intermolecular benzene addition pathway of 5.
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A. Stephen K. Hashmi et al.
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Figure 4. Homo-coupled dimer 8 and its solid state molecular structure.
Scheme 4. Synthesis of gem-diaurated compound 10.
Scheme 5. Isotopic labelling experiments.
analysis of the NMR spectra showed that part of the
deuterium labelling of the terminal alkyne was trans-
ferred to the product. Remarkably, both of the central
double bonds were partially deuterated. The inverse
experiment with undeuterated 3c in deuterated ben-
zene afforded solely non-deuterated 4c. This means
that the partial loss of deuterium in 4c-d must be de-
rived from traces of water in the solvent, no exchange
processes with the solvent benzene are involved.
The suggested mechanism is depicted in Scheme 6.
The catalytic cycle starts with the formation of gold
acetylide complex 9. For further transformation the
second alkyne must be activated by p-coordination of
a molecule of activated gold catalyst (no reaction
took place when acetylide 9 was heated in benzene
without activated catalyst). This dual s/p-activation
Figure 5. Solid state molecular structure of 10.
À
(Figure 5). The gold gold distance of 274.6 pm is mode initiates the formation of highly reactive gold
slightly shorter than in the case of the corresponding vinylidene complex III. Its formation can be ex-
gem-diaurated species derived from the intermolecu- plained by a nucleophilic attack of the b-carbon of
lar benzene addition reaction (276.1 pm).[3] This gold acetylide II onto the p-coordinated alkyne in
strong aurophilic interaction is well in the range of a 5-endo-dig fashion. Gold vinylidene III is most
other reported diaurated species.[9]
probably the same intermediate for the dibenzopenta-
To gain further mechanistic insights, the substrate lene reaction as well as for the b-naphthalene path-
3c-d with a deuterated alkyne was transformed to the way.[3] This is indicated by the competing benzene ad-
corresponding dibenzopentalene (Scheme 5). The dition which was observed with anthracene derivate 5.
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Gold-Catalyzed Synthesis of Dibenzopentalenes – Evidence for Gold Vinylidenes
Scheme 6. Mechanistic rationale.
Furthermore, for some of the reactions, traces of by- ping, formation of a gem-diaurated system and cata-
products showing a mass increase of a benzene mole- lyst transfer) for both of the systems are closely relat-
cule could be detected via GC/MS. If the reaction ed.
proceeds via the dibenzopentalene pathway, the intra-
moleculary offered nucleophilic aromatic carbon
atom attacks the highly electrophilic sp-carbon centre
of the vinylidene species. After that, one of the two
Experimental Section
gold atoms gets proto-demetallated from the proton
General Procedure for the Gold Catalyzed
that is released during rearomatization. In analogy to
Conversions
the organo-gold intermediate of the naphthalene re-
One equivalent of the diyne was dissolved in benzene and
the Au catalyst (5 mol%) was added. The reaction mixture
was stirred at 808C until complete conversion (monitored
by TLC). The solvent was removed under reduced pressure,
and the crude product was purified by flash column chroma-
tography or recrystallized.
action, an equilibrium exists between mono-gold spe-
cies V and gem-diaurated species 10. As gem-diaurat-
ed species 10 binds the active cationic catalyst, the re-
action rates should be strongly dependent on this
equilibrium (apart from the need for the dual activa-
tion, this might be one reason for the need of elevat-
ed reaction temperatures at all). Finally, the last step
consists of a catalyst transfer. The final product is re-
leased and a new molecule of starting material is acti-
vated via s-coordination of a gold atom.[10]
Indeno
ACHTUNGTREN[NGNU 2,1-a]indene (4a): According to the general proce-
dure IPrAuNTf2 (10.7 mg, 12.4 mmol, 5 mol%) was added to
In conclusion, the generation of a reactive gold vi-
nylidene via s/p -dual activation of diyne substrates
offers a complete new reactivity pattern which should
allow a whole series of valuable gold-catalyzed cycli-
zations in the future. If one considers the similarities
between the intramolecular addition of aromatic sub-
stituents that leads to the dibenzopentalene systems
and our recently published formation of b-naphtha-
lenes via the intermolecular pathway; even if the
products are totally different; the elementary reaction
steps (acetylide formation, dual activation of the sub-
a
solution of 1-ethynyl-2-(phenylethynyl)benzene 3a
(50.0 mg, 247 mmol) in benzene (2 mL) and stirred at 808C
for 2 h. The crude product was purified by flash column
chromatography on silica gel (PE) and gave 4a as a red
solid; yield: 27.0 mg (134 mmol, 54%). The 1H NMR data
corresponds to that reported in literature.[9]
.
1H NMR
[(CD3)2SO, 300 MHz]: d=6.64 (s, 2H), 6.87–6.91 (m, 4H),
6.94–6.98 (m, 2H), 7.10–7.15 (m, 2H).
2,3-DimethoxyindenoACHTUNRGTNE[NUG 2,1-a]indene (4b): According to the
strate, gold vinylidene formation, nucleophilic trap- general procedure IPrAuNTf2 (8.25 mg, 9.53 mmol, 5 mol%)
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A. Stephen K. Hashmi et al.
COMMUNICATIONS
silica gel (PE/EA=20:1) and gave 4c-d as a bronze solid;
1
yield: 30.0 mg (122 mmol, 60%). H NMR (C6D6, 300 MHz):
d=5.23 (s, 2H), 5.64–5.66 (m, 0.8H), 5.70–5.73 (m, 0.8H),
6.17 (s, 1H), 6.43 (s, 1H), 6.52–6.56 (m, 1H), 6.63–6.67 (m,
2H), 6.75–6.79 (m, 1H).
2-ButylindenoACHTUNTRGNEUNG[2,1-a]indene (4d): According to the gener-
al procedure IPrAuCl (6.21 mg, 10.0 mmol, 5 mol%) and
was added to a solution of 1-ethACTHNUTRGENUGNynyl-4,5-dimethoxy-2-(ethy-
nylphenyl)benzene 3b (44.0 mg, 168 mmol) in benzene
(2 mL) and stirred at 808C for 1 hour. The crude product
was purified by flash column chromatography on silica gel
(PE/EA=20:1) and gave 4b as a beige solid; yield: 30.0 mg
(114 mmol, 68%); decomp.: 2808C; Rf (PE/EA=2:1)=0.35.
˜
IR (KBr): n=2946, 1633, 1481, 1288, 1216, 1102, 1031, 855,
1
756 cmÀ1; H NMR (CDCl3, 300 MHz): d=3.83 (s, 3H), 3.84
(s, 3H), 6.20 (s, 1H), 6.23 (s, 1H), 6.48 (s, 1H), 6.67 (s, 1H),
13
6.77–6.81 (m, 3H), 6.89–6.96 (m, 1H);
C NMR (CDCl3,
AgPF6 (2.78 mg, 11.0 mmol, 5.5 mol%) were added to a solu-
tion of 1-[(4-butylphenyl)ethynyl]-2-ethynyl-benzene 3d
(50.0 mg, 194 mmol) in benzene (2 mL) and stirred at 508C
for 3 h. The product precipitated, was dissolved in hot ben-
zene and filtrated to remove the silver salt. Evaporation of
the solvent gave 4d as a red solid; yield: 40.0 mg (116 mmol,
60%); decomp.: 2308C; Rf (PE/EA=10:1)=0.58. IR (KBÀr)1:
75 MHz): d=56.1 (q), 56.2 (q), 107.6 (d), 108.1 (d), 121.5
(d), 122.9 (d), 125.3 (d), 126.1 (d), 127.1 (d), 127.9 (s), 127.9
(d), 135.3 (s), 143.5 (s), 148.3 (s), 148.4 (s), 149.1 (s), 149.9
(s), 150.3 (s); MS (EI+, 70 eV): m/z (%)=263 (21) [M+
H]+, 262 (100) [M]+, 247 (27), 219 (29), 218 (12), 204 (13),
176 (15), 162 (6), 151 (8), 131 (7), 113 (5), 88 (8); HR-MS
(EI+, 70 eV): m/z=262.0974 [C18H14O2]+, calcd. for
C18H14O2 (262.30): 262.0994.
˜
n=2958, 2928, 2856, 1455, 1434, 898, 828, 751, 731, 471 cm
;
UV-Vis (DCM): lmax (log e)=279 (4.81), 290 (4.92), 394
1
Indeno[2’,1’:1,2]indenoACTHNUTRGENNU[G 5,6-d]ACHTUNGTERN[NUGN 1,3]dioxole (4c): According
to the general procedure IPrAuNTf2 (8.79 mg, 10.2 mmol,
(4.01), 419 nm (4.11); H NMR (300 MHz, C6D6): d=0.88 (t,
J=7.3 Hz, 3H), 1.21–1.36 (m, 2H), 1.40–1.53 (m, 2H), 2.33
(t, J=7.3 Hz, 2H), 5.98 (d, J=1.5 Hz, 1H), 6.06 (d, J=
1.5 Hz, 1H), 6.53 (s, 1H), 6.57 (d, J=7.5 Hz, 1H), 6.59–6.53
(m, 1H), 6.66–6.71 (m, 2H), 6.84 (d, J=7.5 Hz, 1H), 6.85–
6.90 (m, 1H); 13C NMR (75 MHz, C6D6): d=14.1 (q), 22.6
(t), 33.6 (t), 36.0 (t), 122.3 (d), 122.4 (d), 123.3 (d), 124.1 (d),
125.6 (d), 126.5 (d), 127.3 (d), 127.4 (d), 128.6 (d), 133.1 (s),
135.5 (s), 143.6 (s), 149.7 (s), 150.0 (s), 151.1 (s), 151.2 (s);
MS (EI+, 70 eV): m/z (%)=259 (17) [M+H]+, 258 (84)
[M]+, 251 (19), 215 (100), 201 (25), 151 (53), 113 (39);
HRMS (EI+, 70 eV): C20H18 (258.36), [C20H18]+ calc.:
258.1409, found: 258.1405.
5 mol%) was added to a solution of of 5-ethynyl-6-(ethynyl-
phenyl)-1,3-benzodioxole 3c (50.0 mg, 203 mmol) in benzene
(2 mL) and stirred at 808C for 1 hour. The crude product
was purified by flash column chromatography on silica gel
(PE/EA=20:1) and gave 4c as a bronze solid; yield:
30.0 mg, (122 mmol, 60%); decomp.: 2308C; Rf (PE/EA=
2-MethoxyindenoACTHNUTRGNEUNG[2,1-a]indene (4e): According to the
general procedure IPrAuCl (6.83 mg, 11.0 mmol, 5 mol%)
˜
10:1)=0.48. IR (KBr): n=2960, 2924, 1610, 1494, 1467,
1432, 1363, 1205, 1129, 1043, 934, 861, 748 cmÀ1; H NMR
1
(C6D6, 300 MHz): d=5.24 (s, 2H), 5.66 (d, J=1.7 Hz, 1H),
5.72 (d, J=1.7 Hz, 1H), 6.17 (s, 1H), 6.44 (s, 1H), 6.52–6.57
(m, 1H), 6.62–6.69 (m, 2H), 6.75–6.80 (m, 1H); MS (EI+,
70 eV): m/z (%)=247 (17) [M+H]+, 246 (100) [M]+, 190
(5), 189 (12), 188 (18), 187 (20), 162 (5), 151 (8), 123 (8), 113
(5), 94 (6); HR-MS (EI+, 70 eV): m/z=246.0698
[C17H10O2]+, calcd. for C17H10O2 (246.26): 246.0681.
and AgPF6 (3.03 mg, 12.0 mmol, 5.5 mol%) were added to
a solution of 1-ethynyl-2-[(4-methoxyphenyl)ethynyl]ben-
zene 3e (50.0 mg, 216 mmol) in benzene (2 mL) and stirred
at 808C for 2 h. The product precipitated, was washed with
petroleum ether and ethyl acetate and dissolved in tetrahy-
drofuran to remove the silver salt after filtration. Evapora-
tion of the solvent gave 4e as a brown solid: yield: 40.0 mg
(172 mmol, 80%); decomp.: 2508C; Rf (PE/EA=10:1)=
Indeno[2’,1’:1,2]indenoACTHNUTRGENNU[G 5,6-d]ACHTUNGTERN[NUGN 1,3]dioxole (4c-d): Accord-
ing to the general procedure IPrAuNTf2 (8.79 mg,
˜
0.38. IR (KBr): n=2960, 1602, 1586, 1486, 1431, 1289, 1248,
1225, 1183, 1133, 1036, 855, 819, 751, 729 cmÀ1; UV-Vis
(DCM): lmax (log e)=280 (5.14), 296 (5.22), 393 (3.27),
1
471 nm (3.23); H NMR (300 MHz, C6D6): d=3.26 (s, 3H),
5.91 (s, 2H), 6.21 (dd, J=8.1, 2.4 Hz, 1H), 6.42 (d, J=
2.4 Hz, 1H), 6.59–6.64 (m, 1H), 6.65–6.74 (m, 2H), 6.82 (d,
J=8.1 Hz, 1H), 6.86–6.91 (m, 1H); 13C NMR (75 MHz,
C6D6): d=55.0 (q), 108.1 (s), 110.7 (d), 111.8 (d), 122.4 (d),
123.0 (d), 123.1 (d), 124.4 (d), 125.7 (d), 127.0 (d), 128.8 (d),
10.2 mmol, 5 mol%) was added to a solution of of 5-ethynyl-
6-(ethynylphenyl)-1,3-benzodioxole 3c-d (50.0 mg, 203 mmol)
in benzene (2 mL) and stirred at 808C for 1 hour. The crude
product was purified by flash column chromatography on
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Gold-Catalyzed Synthesis of Dibenzopentalenes – Evidence for Gold Vinylidenes
135.4 (s), 149.3 (s), 151.2 (s), 152.7 (s), 161.3 (s), one carbon
atom not visible; MS (EI+, 70 eV): m/z (%)=233 (19) [M+
H]+, 232 (100) [M]+, 217 (32), 189 (46), 187 (9); HR-MS
(EI+, 70 eV): m/z=232.0877 [C17H12O]+, calcd. for C17H12O
(232.28): 232.0888.
Park, N. Kim, Synlett 2006, 17, 2781–2784; d) J. Zhao,
C. O. Hughes, F. D. Toste, J. Am. Chem. Soc. 2006, 128,
7436–7437; e) J.-J. Lian, P.-C. Chen, Y.-P. Lin, H.-C.
Ting, R.-S. Liu, J. Am. Chem. Soc. 2006, 128, 11372–
11373; f) C. H. Oh, A. Kim, New J. Chem. 2007, 31,
1719–1721; g) J.-J. Lian, R.-S. Liu, Chem. Commun.
2007, 1337–1339; h) A. Das, H.-K. Chang, C.-H. Yang,
R.-S. Liu, Org. Lett. 2008, 10, 4061–4064; i) H.-S. Yeom,
J.-E. Lee, S. Shin, Angew. Chem. 2008, 120, 7148–7151;
Angew. Chem. Int. Ed. 2008, 47, 7040–7043; j) C.
Zhang, D.-M. Cui, L.-Y. Yao, B.-S. Wang, Y.-Z. Hu, T.
Hayashi, J. Org. Chem. 2008, 73, 7811–7813; k) J.-M.
Tang, T.-A. Liu, R.-S. Liu, J. Org. Chem. 2008, 73,
8479–8483; l) C. H. Oh, A. Kim, Synlett 2008, 5, 777–
781; m) S. Md. A. Sohel, R.-S. Liu, Chem. Soc. Rev.
2009, 38, 2269–2281; n) C. Sperger, A. Fiksdahl, Org.
Lett. 2009, 11, 2449–2452; o) J. Meng, Y.-L. Zhao, C.-Q.
Ren, Y. Li, Z. Li, Q. Liu, Chem. Eur. J. 2009, 15, 1830–
1834; p) Y. Odabachian, X. F. Le Goff, F. Gagosz,
Chem. Eur. J. 2009, 15, 8966–8970; q) C. H. Oh, S. Kar-
makar, J. Org. Chem. 2009, 74, 370–374; r) S. Kramer,
J. L. H. Madsen, M. Rottlꢀnder, T. Skrydstrup, Org.
Lett. 2010, 12, 2758–2761; s) C. A. Sperger, A. Fiksdahl,
J. Org. Chem. 2010, 75, 4542–4553; t) D.-M. Cui, Y.-N.
Ke, D.-W. Zhuang, Q. Wang, C. Zhang, Tetrahedron
Lett. 2010, 51, 980–982; u) A. S. K. Hashmi, M. Bührle,
M. Wçlfle, M. Rudolph, M. Wieteck, F. Rominger, W.
Frey, Chem. Eur. J. 2010, 16, 9846–9854; v) K. Hirano,
Y. Inaba, T. Watanabe, S. Oishi, N. Fujii, H. Ohno,
Adv. Synth. Catal. 2010, 352, 368–372; w) C. Sperger,
L. H. S. Strand, A. Fiksdahl, Tetrahedron 2010, 66,
7749–7754; x) Y. Chen, G. Li, Y. Liu, Adv. Synth. Catal.
2011, 353, 392–400; y) P. Nun, S. Dupuy, S. Gaillard, A.
Poater, L. Cavallo, S. P. Nolan, Catal. Sci. Technol.
2011, 1, 58–61; z) A. S. K. Hashmi, T. Hꢀffner, M. Ru-
dolph, F. Rominger, Chem. Eur. J. 2011, 17, 8195–8201;
aa) K. Hirano, Y. Inaba, N. Takahashi, M. Shimano, S.
Oishi, N. Fujii, H. Ohno, J. Org. Chem. 2011, 76, 1212–
1227; ab) D.-H. Zhang, L.-F. Yao, Y. Wie, M. Shi,
Angew. Chem. 2011, 123, 2631–2635; Angew. Chem.
Int. Ed. 2011, 50, 2583–2587.
Thiopheneindeno
ACHTUNGTRENN[UNG 2,1-a]indene (4h): According to the
general procedure IPrAuCl (7.45 mg, 12.0 mmol, 5 mol%)
and AgPF6 (3.29 mg, 13.0 mmol, 5.5 mol%) were added to
solution of 2-[(2-ethynylphenyl)ethynyl]thiophene 3h
a
(50.0 mg, 240 mmol) in benzene (2 mL) and stirred at 808C
for 2 h. The crude product was purified by flash column
chromatography on silica gel (PE) and gave 4h as a yellow
solid; yield: (10.4 mg, 50.0 mmol, 20%); decomp.: 2308C; Rf
˜
(PE/EA=10:1)=0.51. IR (KBr): n=3070, 1715, 1636, 1456,
1254, 831, 759, 748, 690, 649 cmÀ1; UV-Vis (DCM): lmax (log
e)=282 (4.44), 289 (4.44), 393 (3.74), 471 nm (3.69);
1H NMR (300 MHz, CDCl3) d=5.98 (d, J=1.8 Hz, 1H),
6.06 (d, J=1.8 Hz, 1H), 6.50 (d, J=4.8 Hz, 1H), 6.61–6.72
(m, 4H), 6.91 (d, J=4.8 Hz, 1H); 13C NMR (75 MHz,
CDCl3): d=121.1 (d), 121.3 (d), 122.1 (d), 123.7 (d), 128.0
(d), 128.6 (d), 128.8 (d), 136.6 (s), 145.0 (s), 150.3 (s), 152.1
(s), 157.0 (s), 2 carbon atoms not visible; MS (EI+, 70 eV):
m/z (%)=209 (17) [M+H]+, 208 (100) [M]+, 164 (8), 163
(16), 151 (8), 113 (7); HR-MS (EI+, 70 eV): m/z=208.0361
[C14H8S]+, calcd. for C14H8S (208.28): 208.0347.
Acknowledgements
LJ is grateful to the EU for an Erasmus fellowship. The au-
thors thank Umicore AG & Co. KG for the generous dona-
tion of gold salts.
[3] A. S. K. Hashmi, I. Braun, M. Rudolph, F. Rominger,
Organometallics 2012, 31, 644–661.
References
[4] a) V. Mamane, P. Hannen, A. Fürstner, Chem. Eur. J.
2004, 10, 4556–4575; b) E. Soriano, M. Contelles, Orga-
nometallics 2006, 25, 4542–4553; c) I. V. Seregin, V. Ge-
vorgyan, J. Am. Chem. Soc. 2006, 128, 12050–12051;
d) V. Lavallo, G. D. Frey, S. Kouzar, B. Donnadieu, G.
Bertrand, Proc. Natl. Acad. Sci. USA 2007, 104, 13569–
13573; e) I. V. Seregin, A. W. Schammel, V. Gevorgyan,
Tetrahedron 2008, 64, 6876–6883; f) Y. Xia, A. S.
Dudnik, Y. Li, V. Gevorgyan, Org. Lett. 2010, 12, 5538–
5541.
[1] a) A. S. K. Hashmi, G. J. Hutchings, Angew. Chem.
2006, 118, 8064–8105; Angew. Chem. Int. Ed. 2006, 45,
7896–7936; b) E. Jimꢂnez-Nfflnez, A. M. Echavarren,
Chem. Commun. 2007, 333–346; c) R. Skouta, C.-J. Li,
Tetrahedron 2008, 64, 4917–4938; d) Z. Li, C. Brouwer,
C. He, Chem. Rev. 2008, 108, 3239–3265; e) A. Arcadi,
Chem. Rev. 2008, 108, 3266–3325; f) D. J. Gorin, B. D.
Sherry, F. D. Toste, Chem. Rev. 2008, 108, 3351–3378;
g) A. S. K. Hashmi, M. Rudolph, Chem. Soc. Rev. 2008,
37, 1766–1775; h) S. Sengupta, X. Shi, ChemCatChem
2010, 2, 609–619; i) C. Nevado, Chimia 2010, 64, 247–
251; j) A. Corma, A. Leyva-Pꢂrez, M. J. Sabater, Chem.
Rev. 2011, 111, 1657–1712; k) A. S. K. Hashmi, M. Ru-
dolph, Chem. Commun. 2011, 47, 6536–6544.
[5] See Supporting Information for the detailed experi-
mental procedures.
[6] For alternative routes towards dibenzopentalenes see:
a) K. Brand, Ber. Dtsch. Chem. Ges. 1912, 45, 3071–
3077; b) C. T. Blood, R. P. Linstead, J. Chem. Soc. 1952,
2263–2268; c) M. P. Cava, R. Pohlke, M. J. Mitchell, J.
Org. Chem. 1963, 28, 1861–1863; d) V. E. Müller, K.
Munk, P. Ziemek, M. Sauerbier, Justus Liebigs Ann.
Chem. 1968, 713, 40–48; e) V. E. Müller, K. Munk, H.-
[2] a) T. Shibata, R. Fujiwara, D. Takano, Synlett 2005, 13,
2062–2066; b) A. Odedra, C.-J. Wu, T. B. Pratap, C.-W.
Huang, Y.-F. Ran, R.-S. Liu, J. Am. Chem. Soc. 2005,
127, 3406–3412; c) C. H. Oh, A. Kim, W. Park, D. I.
Adv. Synth. Catal. 2012, 354, 555 – 562
ꢁ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
561

A. Stephen K. Hashmi et al.
COMMUNICATIONS
G. Fritz, M. Sauerbier, Justus Liebigs Ann. Chem. 1969,
723, 76–82; f) D. Hellwinkel, H.-J. Hasselbach, F. Lꢀm-
merzahl, Angew. Chem. 1984, 96, 713–714; Angew.
Chem. Int. Ed. Engl. 1984, 23, 705–706; g) M. Ballester,
J. CastaÇer, J. Riera, O. Armet, J. Org. Chem. 1986, 51,
1100–1105; h) M. R. Anderson, R. F. C. Brown, K. J.
Coulston, F. W. Eastwood, A. Ward, Aust. J. Chem.
1990, 43, 1137–1150; i) Y. Badrieh, J. Blum, I. Amer,
K. P. C. Vollhardt, J. Mol. Catal. 1991, 66, 295–312; j) Y.
Badrieh, A. Greenwald, H. Schumann, J. Blum, Chem.
Ber. 1992, 125, 667–674; k) R. F. C. Brown, F. W. East-
wood, N. R. Wong, Tetrahedron Lett. 1993, 34, 3607–
3608; l) J. Blum, W. Baidossi, Y. Badrieh, R. E. Hoff-
mann, H. Schumann, J. Org. Chem. 1995, 60, 4738–
4742; m) M. Chakraborty, C. A. Tessier, W. J. Youngs,
J. Org. Chem. 1999, 64, 2947–2949; n) J. Yang, M. V.
Lakshmikantham, M. P. Cava, D. Lorcy, J. R. Bethelot,
J. Org. Chem. 2000, 65, 6739–6742; o) D. V. Preda, L. T.
Scott, Org. Lett. 2000, 2, 1489–1492; p) J. K. Kendall,
H. Shechter, J. Org. Chem. 2001, 66, 6643–6649; q) M.
Saito, M. Nakamura, T. Tajima, M. Yoshioka, Angew.
Chem. 2007, 119, 1526–1529; Angew. Chem. Int. Ed.
2007, 46, 1504–1507; r) M. Saito, M. Nakamura, T.
Tajima, Chem. Eur. J. 2008, 14, 6062–6068; s) G. Babu,
A. Orita, J. Otera, Chem. Lett. 2008, 37, 1296–1297;
t) T. Kawase, A. Konishi, Y. Hirao, K. Matsumoto, H.
Kurata, T. Kubo, Chem. Eur. J. 2009, 15, 2653–2661;
u) Z. U. Levi, T. D. Tilley, J. Am. Chem. Soc. 2009, 131,
2796–2797; v) H. Zhang, T. Karasawa, H. Yamada, A.
Wakamiya, S. Yamaguchi, Org. Lett. 2009, 11, 3076–
3079; w) J. L. Jeffrey, R. Sarpong, Tetrahedron Lett.
2009, 50, 1969–1972; x) D. Wang, T. Michinobu, J.
Polym. Sci. Part A 2010, 49, 72–81; y) T.-C. Wu, C.-C.
Tai, H.-C. Tiao, M.-Y. Kuo, Y.-T. Wu, Chem. Eur. J.
2011, 17, 1930–1935. For a review about synthesis and
reactions of dibenzopentalenes, see: z) M. Saito, Sym-
metry 2010, 2, 950–969.
[7] CCDC 859060 (4a), CCDC 859061 (6), CCDC 859062
(8) and CCDC 859063 (10) contain the supplementary
crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
[8] a) A. S. K. Hashmi, M. C. Blanco, D. Fischer, J. W.
Bats, Eur. J. Org. Chem. 2006, 1387–1389; b) A. S. K.
Hashmi, T. D. Ramamurthi, F. Rominger, J. Organo-
met. Chem. 2009, 694, 592–597; c) A. S. K. Hashmi,
T. D. Ramamurthi, M. H. Todd, A. S.-K. Tsang, K.
Graf, Aust. J. Chem. 2010, 63, 1619–1626.
À
[9] Au Au distances for gem-diaurated compounds found
in the literature: 272.7–284.6 pm. Average value (7
structures): 277.8 pm; a) A. N. Nesmeyanov, E. G. Pere-
valova, K. I. Grandberg, D. A. Lemenovskii, T. V. Bau-
kova, O. B. Afanassova, J. Organomet. Chem. 1974, 65,
131–144; b) V. G. Andrianov, Y. T. Struchkov, E. R.
Rossinskaya, J. Struct. Chem. 1974, 15, 65–72; c) H.
Schmidbaur, Y. Inoguchi, Chem. Ber. 1980, 113, 1646–
1653; d) R. Usón, A. Laguna, E. J. Fernµndez, A.
Mendia, P. G. Jones, J. Organomet. Chem. 1988, 350,
129–138; e) K. A. Porter, A. Schier, H. Schmidbaur,
Organometallics 2003, 22, 4922–4927; f) M. Osawa, M.
Hoshino, D. Hashizume, Dalton Trans. 2008, 2248–
2252; g) G. Seidel, C. W. Lehmann, A. Fürstner,
Angew. Chem. 2010, 122, 8644–8648; Angew. Chem.
Int. Ed. 2010, 49, 8466–8470.
[10] For a detailed discussion of the catalyst transfer step,
see ref.[3]
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Adv. Synth. Catal. 2012, 354, 555 – 562