Palladium-catalyzed 1,2-addition of organic halides and terminal alkynes to 7-oxabenzonorbornadiene: An efficient route to polyaromatic hydrocarbons

Article abstract of DOI:10.1002/ejoc.200700772

A three-component coupling reaction of organic halides with oxabicyclic alkenes and terminal alkynes was catalyzed by a palladium complex and a phase-transfer agent in the presence of aqueous NaOH. The reaction gave a series of 5,6-disubstituated 7-oxabenzonorbornene derivatives in good yields. The disubstituted products from oxabenzonorbornadiene can be readily converted into polyaromatic hydrocarbons by a Lewis acid mediated deoxyaromatization reaction. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejoc.200700772

FULL PAPER
DOI: 10.1002/ejoc.200700772
Palladium-Catalyzed 1,2-Addition of Organic Halides and Terminal Alkynes to
7-Oxabenzonorbornadiene: An Efficient Route to Polyaromatic Hydrocarbons
Chun-Jung Kuo,[a] Shu-Jin Cheng,[a] Shu-Ting Chang,[a] and Charng-Hsing Liu*[a]
Keywords: Multicomponent reactions / Palladium / Oxabenzonorbornadiene / Alkynes
A three-component coupling reaction of organic halides with
oxabicyclic alkenes and terminal alkynes was catalyzed by a
palladium complex and a phase-transfer agent in the pres-
ence of aqueous NaOH. The reaction gave a series of 5,6-
disubstituated 7-oxabenzonorbornene derivatives in good
yields. The disubstituted products from oxabenzonorbornadi-
ene can be readily converted into polyaromatic hydrocarbons
by a Lewis acid mediated deoxyaromatization reaction.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
Introduction
alkynols, organostannanes, and tetraphenylborate ions.
Transition-metal-catalyzed ternary coupling reactions of However, there is great restriction on the type of olefin that
organic halides, nucleophiles, and olefins is an important can be used in the ternary coupling reactions. These olefins
method for the construction of complex molecular struc- generally require high coordination and insertion ability,
tures in a single one-pot step.[1] In this type of multicompo- but they must also lack β-hydrogen atoms so that elimi-
nent reaction, the electrophiles employed include various nation after insertion is not possible. Bicyclic olefins such
aryl- and alkenyl halides, iodonium salts, and diazonium as norbornadienes and norbornenes are a class of olefins
salts, and the nucleophiles[2–5] typically used are 1-alkynes, that show the above properties due to the angle strain of
Scheme 1. Oxabenzonorbornadiene treated with organic halides and 1-alkynes in the presence of Pd(PPh3)4, Bu4NI, and NaOH to give
5,6-disubstituated 7-oxabenzonorbornene derivatives.
the carbon–carbon double bonds. In our previous studies,[6]
[a] Department of Applied Chemistry, Chia Nan University of
Pharmacy and Science,
we observed a palladium-catalyzed three-component coup-
ling reaction of norbornadiene with a 1-haloalkyne and a
terminal alkyne to produce 5,6-dialkynyl norbornene. Al-
Tainan 717, Taiwan
Fax: +886-6-2667319
E-mail: liuchs@mail.chna.edu.tw
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C.-J. Kuo, S.-J. Cheng, S.-T. Chang, C.-H. Liu
FULL PAPER
though 7-oxabicyclic alkenes are similar to norbornadienes transfer catalyst. The disubstituted products underwent de-
and norbornenes, the transition-metal-catalyzed addition oxyaromatization readily in the presence of BF3·OEt2 to
reaction of a nucleophilic[7–13] or electrophilic[14] reagent to provide an efficient method for the synthesis of variously
a 7-oxabicyclic alkene often leads to ring opening of the substituted polyaromatics.
oxabicyclic alkene because of facile β-oxygen elimination
after the addition of an organic group to the oxabicyclic
alkene. As a result, it is difficult to add a nucleophile or an
electrophile in one pot to give a three-component coupling
Results and Discussion
reaction product for reactions involving 7-oxabicyclic al-
The three-component coupling reaction of iodobenzene
kenes as substrates. In this study, we report a palladium- (2a; 1.73 mmol), phenylacetylene (3a; 1.73 mmol), and 7-
catalyzed three-component coupling reaction of oxabicyclic oxabenzonorbornadiene (1a; 1.73 mmol) was carried out at
alkenes with organic halides and terminal alkynes to pro- 40 °C for 24 h in CH2Cl2/NaOH (5  in water) in the pres-
vide 5,6-disubstituated 7-oxabenzonorbornene derivatives ence of tetrabutylammonium iodide (0.173 mmol) and
in good yields (Scheme 1). The catalytic reaction was car- Pd(PPh3)4 (0.087 mmol) to give 5,6-disubstituated 7-oxa-
ried out in the presence of aqueous NaOH and a phase- benzonorbornene derivative 4a in 92% yield (Table 1, En-
Table 1. 5,6-Addition products of 1-alkyne 3 and aryl and alkenyl halides 2 to oxabicyclic alkene 1 in the presence of Pd(PPh3)4.
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An Efficient Route to Polyaromatic Hydrocarbons
try 1). The structure of 4a was characterized by NMR and Entries 7, 10, and 12) gave higher product yields than that
IR spectroscopy and mass spectrometry. In the absence of obtained with a substrate having a strong electron-with-
a palladium complex or sodium hydroxide, product 4a was drawing group (Table 1, Entry 13) in the ternary coupling
not found, whereas the omission of a phase-transfer rea- reaction.
gent, tetrabutylammoniun iodide, afforded only a trace
The reaction could be further applied to alkyl and alk-
amount of desired product 4a. The exo and cis stereochem- enyl iodides and a 1-bromoalkyne. Under similar reaction
istry of 4k was confirmed by X-ray diffraction[15] (Figure 1). conditions, 2-iodothiophene (2k) and 3-iodocyclohex-2-en-
The catalytic reaction is remarkably stereoselective and af- one (2l) coupled to 7-oxabenzonorbornadiene (1a) and
fords only to the exo and cis product.
phenylacetylene (3a) to obtain 4p and 4q in 56 and 28%
yield, respectively (Table 1, Entries 16 and 17). Similarly,
the reactions of methyl iodide (2m) and 1-bromo-2-phenyl-
acetylene (2n) with 7-oxabenzonorbornadiene (1a) and
phenylacetylene (3a) afforded 4r and 4s in 36 and 45%
yield, respectively (Table 1, Entries 18 and 19). In most of
these three-component coupling reactions, direct coupling
products between 2 and 3 were observed in various
amounts. The side reactions likely account for the low yield
of product 4 in some of the cases in Table 1.
Bicyclic alkenes could also be used in the ternary coup-
ling reaction; thus, the coupling of 1b with iodobenzene
(2a) and phenylacetylene (3a) under similar reaction condi-
tions afforded product 4t in 80% yield (Table 1, Entry 20).
In the same way, the coupling reaction of bulky 1,4-epoxy-
1,4-dihydrotriphenylene (1c) with iodobenzene (2a) and
phenylacetylene (3a) generated product 4u in 72% yield
(Table 1, Entry 21).
Figure 1. ORTER diagram of 4k.
On the basis of the observed regiochemistry of the prod-
To understand the nature of this palladium-catalyzed ucts and classical carbopalladation chemistry, a reasonable
1,2-addition, the effect of solvent, base, and metal complex catalytic reaction mechanism was proposed (Scheme 2). The
used in the three-component coupling reaction of 1a, 2a, first step is likely the oxidative addition of the aryl halide
and 3a to give 4a was investigated. The palladium com- to the Pd0 species to give arylpalladium(II) intermediate A.
plexes Pd(dba)2 and Pd(dba)2/2dppe afforded a trace Substitution of a phosphane ligand in A by 7-oxabenzonor-
amount of 4a only, whereas Pd(dba)2/2dppp gave product bornadiene (1a) by exo coordination followed by insertion
4a in 24% yield. Pd(PPh3)4 was found to be the best cata- of the carbon–carbon double bond into the oxabenzonor-
lyst, as it afforded product 4a in 92% yield. The solvent bornene moiety leads to intermediate B.[16] Then, the coor-
used for the catalytic reaction is also critical. Dichlorometh- dinated iodine in intermediate B can be replaced by an ace-
ane was more effective than toluene, and product 4a was tylide to afford palladium intermediate C. Reductive elimi-
obtained in 92 and 74% yield, respectively. The use of Et3N nation gives the final 5,6-disubstituated 7-oxabenzonorbor-
as base gave product 4a in 45% yield, which is lower than nene derivative 4 to regenerated the Pd0 catalyst.
the 92% yield obtained by using NaOH as the base. On the
It is known that the addition of aryl halides to 7-oxaben-
basis of these studies, the optimized reaction conditions for zonorbornadiene (1a) catalyzed by palladium and nickel
the three-component coupling reaction are: Pd(PPh3)4 in complexes often results in the isolation of ring-opening
the presence of Bu4NI in CH2Cl2/NaOH (5 ) at 40 °C. products because of facile β-oxygen elimination of the oxa-
These reactions conditions were employed as the standard bicyclic alkene moiety in intermediate B.[13d,14] However, in
for the reactions shown in Table 1.
the present three-component coupling reaction, ring open-
This palladium-catalyzed three-component coupling re- ing due to C–O bond cleavage does not occur. The results
action was successfully extended to various organic halides indicate that the substitution of the iodide ligand in inter-
and 1-alkynes. The results are summarized in Table 1. Treat- mediate B by the acetylide to give intermediate C is likely
ment of iodobenzene and 7-oxabenzonorbornadiene (1a) much faster than β-oxygen elimination of B under the pres-
with terminal alkynes 3a–f (Table 1, Entries 1–6) furnished ent catalytic reaction conditions.
corresponding 5,6-disubstituted 7-oxabenzonorbornene de-
5,6-Disubstituated 7-oxabenzonorbornene derivatives 4a,
rivatives 4a–f in 18–92% yield. It is noteworthy that the 4g, 4j, and 4l readily undergo deoxyaromatization in the
yield of this three-component coupling reaction is substan- presence of BF3·OEt2 (2 equiv.) as a Lewis acid in CH2Cl2
tially affected by the position of the substituent on the aryl at room temperature over 1 h to provide polyaromatic com-
iodide. ortho-Substituted aryl iodide gave a slightly lower pounds 5a, 5b, 5c, and 5d in 60, 78, 83, and 65% yield,
yield relative to those of the meta and para derivatives respectively (Scheme 3). The structures of these polyarom-
(Table 1, Entries 7–11). In addition, aryl iodides bearing an atic compounds were characterized by NMR and IR spec-
electron-donating substituent in the para position (Table 1, troscopy and mass spectrometry. The structure of com-
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C.-J. Kuo, S.-J. Cheng, S.-T. Chang, C.-H. Liu
FULL PAPER
Scheme 2. Proposed mechanism for the palladium-catalyzed 1,2-addition.
pound 5a was confirmed by X-ray diffraction[15] (Figure 2). alkenes and terminal alkynes to afford products with ex-
It is interesting to note that most of these polyaromatic hy- tremely high stereoselectivity in good yields. The disubsti-
drocarbon derivatives show strong photoluminescence in tuted products from oxabenzonorbornadiene can be further
the solid state and in solution and are potentially useful as applied to the synthesis of polyaromatic hydrocarbons by
electroluminescent and photoluminescent materials.[17]
a deoxyaromatization reaction. Further application of the
methodology in organic synthesis and detailed mechanistic
studies of the catalytic reaction are in progress.
Experimental Section
General Section: All reactions were performed under a dry nitrogen
atmosphere. All chemicals were obtained from commercial suppli-
ers and used without further purification unless otherwise noted.
Oxabenzonorbornadienes 1b,c were prepared following literature
procedures.[18] The complex Pd(PPh3)4 was prepared according to
the published procedures.[19] 1H and 13C NMR experiments were
performed with a Bruker 200 instrument. Infrared spectra were ob-
tained with a PerkinElmer System 2000 spectrometer. Mass spectra
at high resolution were recorded with a Thermo Finnigan MAT 95
XL instrument.
Scheme 3. Deoxyaromatization reaction of compound 4 with
BF3·OEt2 to afford corresponding product 5.
General Procedure for the Three-Component Coupling Reaction: In
a typical procedure, a round-bottom flask containing Pd(PPh3)4
(0.087 mmol) and (n-butyl)4NI (0.173 mmol) was purged with ni-
trogen three times. To the flask was added sequentially 7-oxaben-
zonorbornadiene (1.73 mmol), iodobenzene (1.73 mmol), 1-alkyne
(1.73 mmol), CH2Cl2 (5 mL), and NaOH (5 , 10 mL). The solu-
tion was then stirred at 40 °C for 24 h. After filtration through
Celite, the filtrate was concentrated and then separated on a silica
gel column (hexane/ethyl acetate) to give desired product 4.
5-exo-Phenyl-6-exo-(2-phenylethynyl)-7-oxabenzonorbornene (4a):
Yield: 513 mg (92%), m.p. 135–136 °C. 1H NMR (200 MHz,
CDCl3): δ = 3.27 (s, 2 H), 5.53 (s, 1 H), 5.57 (s, 1 H), 6.90–6.97
(m, 2 H), 7.11–7.7.50 (m, 12 H) ppm. 13C NMR (50 MHz, CDCl3):
δ = 40.8 (d), 50.8 (d), 84.7 (d), 85.2 (d). 85.7 (s), 89.4 (s), 119.2 (d),
119.6 (d), 123.4 (s), 126.6 (d), 127.0 (d), 127.3 (d), 127.6 (d), 127.9
(d), 129.2 (d), 131.4 (d), 141.0 (s), 145.1 (s), 145.9 (s) ppm. IR
(KBr): 3025.4, 1597.2, 1458.9, 1193.8, 750.3, 691.7 cm–1. HRMS:
calcd. for C24H18O 322.1358; found 322.1357. C24H18O (322.40):
calcd. C 89.41, H 5.63, found C 89.06, H 5.65.
Figure 2. ORTER diagram of 5a.
Conclusions
We developed a novel palladium-catalyzed three-compo-
5-exo-[2-(4-Methoxyphenyl)ethynyl]-6-exo-phenyl-7-oxabenzonor-
nent coupling reaction of organic halides with oxabicyclic bornene (4b): Yield: 512 mg (84 %), m.p. 152–153 °C. 1H NMR
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An Efficient Route to Polyaromatic Hydrocarbons
(200 MHz, CDCl3): δ = 3.26 (s, 2 H), 3.74 (s, 3 H), 5.53 (s, 1 H),
5.56 (s, 1 H), 6.68 (d, J = 8.7 Hz, 2 H), 6.86 (d, J = 8.7 Hz, 2 H),
7.18–7.51 (m, 9 H) ppm. 13C NMR (50 MHz, CDCl3): δ = 40.7
(d), 50.7 (d), 55.1 (q), 84.8 (d), 85.2 (d). 85.5 (s), 87.8 (s), 113.5 (d),
115.5 (s), 119.2(d), 119.6 (d), 126.6 (d), 127.0 (d), 127.2 (d), 127.9
(d), 129.2 (d), 132.7 (d), 141.1 (s), 145.1 (s), 145.9 (s), 159.0 (s)
ppm. IR (KBr): 3015.8, 2947.0, 1610.0, 1522.9, 1244.4, 836.7,
744.9, 698.4 cm–1. HRMS: calcd. for C25H20O2 352.1463; found
352.1462. C25H20O2 (352.43): calcd. C 85.20, H 5.72; found C
84.82, H 5.59.
336.1514; found 336.1517. C25H20O (336.43): calcd. C 89.25, H
5.99; found C 89.18, H 5.96.
5-exo-(2-Phenylethynyl)-6-exo-m-tolyl-7-oxabenzonorbornene (4h):
Yield: 483 mg (83 %), m.p. 125–126 °C. 1H NMR (200 MHz,
CDCl3): δ = 2.35 (s, 3 H), 3.22 (d, AB type, J = 8.6 Hz, 1 H),
3.26(d, AB type J = 8.6 Hz, 1 H), 5.51 (s, 1 H), 5.57 (s, 1 H),
6.92–7.02 (m, 2 H), 7.05–7.41 (m, 11 H) ppm. 13C NMR (50 MHz,
CDCl3): δ = 21.5 (q), 40.7 (d), 50.8 (d), 84.8 (d), 85.3 (d). 85.7 (s),
89.5 (s), 119.1 (d), 119.7 (d), 123.5 (s), 126.4 (d), 126.9 (d), 127.2
(d), 127.4 (d), 127.5 (d), 127.8 (d), 127.9 (d), 129.9 (d), 131.4 (d),
137.4 (s), 140.8 (s), 145.1 (s), 146.00 (s) ppm. IR (KBr): 3048.5,
2927.8, 1597.1, 1459.7, 1153.0, 898.8, 758.4, 691.9 cm–1. HRMS:
5-exo-Phenyl-6-exo-(2-p-tolylethynyl)-7-oxabenzonorbornene (4c):
Yield: 396 mg (68 %), m.p. 137–139 °C. 1H NMR (200 MHz,
CDCl3): δ = 2.18 (s, 3 H), 3.18 (s, 2 H), 5.45 (s, 1 H), 5.49 (s, 1 H), calcd. for C25H20O 336.1514; found 336.1513. C25H20O (336.43):
6.76 (d, J = 8.1 Hz, 2 H), 6.88 (d, J = 8.1 Hz, 2 H), 7.10–7.43 (m, calcd. C 89.25, H 5.99; found C 89.01, H 6.02.
9 H) ppm. 13C NMR (50 MHz, CDCl3): δ = 21.3 (q), 40.7 (d), 50.7
(d), 84.7 (d), 85.2 (d). 85.7 (s), 88.6 (s), 119.1 (d), 119.6 (d), 120.3
(s), 126.6 (d), 127.0 (d), 127.2 (d), 127.9 (d), 128.7 (d), 129.2 (d),
5-exo-(2-Phenylethynyl)-6-exo-o-tolyl-7-oxabenzonorbornene (4i):
Yield: 303 mg (52 %), m.p. 163–165 °C. 1H NMR (200 MHz,
CDCl3): δ = 2.20 (s, 3 H), 3.33 (d, AB type, J = 8.5 Hz, 1 H), 3.39
(d, AB type, J = 8.5 Hz, 1 H), 5.58 (s, 1 H), 5.71 (s, 1 H), 6.78–
6.91 (m, 2 H), 7.05–7.43 (m, 10 H), 7.68 (d, J = 7.6 Hz, 1 H) ppm.
13C NMR (50 MHz, CDCl3): δ = 20.2 (q), 39.5 (d), 46.8 (d), 83.9
(d), 84.8 (d). 88.6 (s), 119.2(d), 119.7 (d), 123.3 (s), 126.0 (d), 126.4
131.2 (d), 137.5 (s), 141.00 (s), 145.1 (s), 145.9 (s) ppm. IR (KBr):
3026.8, 2923.9, 1603.2, 1494.7, 1264.1, 817.3, 753.3, 700.4 cm–1
.
HRMS: calcd. for C25H20O 336.1514; found 336.1515. C25H20O
(336.43): calcd. C 89.25, H 5.99; found C 89.05, H 6.03.
5-exo-[2-(4-Acetylphenyl)ethynyl]-6-exo-phenyl-7-oxabenzonor- (d), 127.0 (d), 127.3 (d), 127.5 (d), 127.8 (d), 129.6 (d), 131.5 (d),
bornene (4d): Yield: 114 mg (18 %), m.p. 149–151 °C. 1H NMR
(200 MHz, CDCl3): δ = 2.54 (s, 3 H), 3.30 (s, 2 H), 5.57 (s, 1 H),
136.8 (s), 139.5 (s), 145.3 (s), 146.2 (s) ppm. IR (KBr): 3021.0,
2915.5, 1598.9, 1487.6, 978.8, 900.2, 710.0 cm–1. HRMS: calcd. for
5.59 (s, 1 H), 7.00 (d, J = 8.2 Hz, 2 H), 7.21–7.50 (m, 9 H), 7.77 C25H20O 336.1514; found 336.1511. C25H20O (336.43): calcd. C
(d, J = 8.1 Hz, 2 H) ppm. 13C NMR (50 MHz, CDCl3): δ = 26.5 89.25, H 5.99; found C 88.93, H 5.87.
(q), 40.9 (d), 50.8 (d), 84.5 (d), 85.1 (d). 93.2 (s), 119.2 (d), 119.7
(d), 126.7 (d), 127.1 (d), 127.4 (d), 127.9 (d), 128.0 (d), 128.3 (s),
129.1 (d), 131.4 (d), 135.7 (s), 140.8 (s), 144.9 (s), 145.8 (s), 197.3
5-exo-(4-Methoxyphenyl)-6-exo-(2-phenylethynyl)-7-oxabenzonor-
bornene (4j): Yield: 450 mg (77 %), m.p. 99–100 °C. 1H NMR
(200 MHz, CDCl3): δ = 3.15 (s, 2 H), 3.73 (s, 3 H), 5.39 (s, 1 H),
(s) ppm. IR (KBr): 3062.7, 2998.8, 1669.8, 1598.7, 1460.8, 1273.2,
5.48 (s, 1 H), 6.81 (d, J = 8.7 Hz, 2 H), 6.87–6.98 (m, 2 H), 7.04–
830.4, 776.5, 703.5 cm–1. HRMS: calcd. for C26H20O2 364.1463;
7.34 (m, 7 H), 7.30 (d, J = 8.7 Hz, 2 H) ppm. 13C NMR (50 MHz,
found 364.1461. C26H20O2 (364.44): calcd. C 85.69, H 5.53; found
C 85.63, H 5.32.
CDCl3): δ = 40.8 (d), 50.1 (d), 55.4 (q), 84.8 (d), 85.5 (d). 85.7 (s),
89.6 (s), 113.4 (d), 119.2(d), 119.6 (d), 123.5 (s), 127.0 (d), 127.3
5-exo-(Hex-1-ynyl)-6-exo-phenyl-7-oxabenzonorbornene (4e): Yield:
199 mg (38 %). 1H NMR (200 MHz, CDCl3): δ = 0.98 (t, J =
7.2 Hz, 3 H), 1.78–1.42 (m, 4 H), 2.03–2.18 (m, 2 H), 3.26 (dt, J =
(d), 127.6 (d), 127.9 (d), 130.2 (d), 131.4 (d), 133.1 (s), 145.1 (s),
145.9 (s), 158.6 (s) ppm. IR (KBr): 3016.8, 2930.0, 1609.0, 1462.9,
1246.2, 846.7, 765.2, 695.6 cm–1. HRMS: calcd. for C25H20O2
8.6, 2.2 Hz, 1 H), 3.36 (d, J = 8.6 Hz, 1 H), 5.65 (s, 1 H), 5.67 (s, 352.1463; found 352.1463. C25H20O2 (352.43): calcd. C 85.20, H
1 H), 7.27–7.77 (m, 9 H) ppm. 13C NMR (50 MHz, CDCl3): δ = 5.72; found C 85.27, H 5.69.
13.6 (q), 18.3 (t), 21.6 (t), 30.5 (t), 40.1 (d), 50.5 (d), 79.3 (s), 85.1
(d), 85.2 (d), 85.9 (s), 119.1 (d), 119.6 (d), 126.4 (d), 126.9 (d), 127.1
(d), 127.7 (d), 129.2 (d), 141.2 (s), 145.2 (s), 145.9 (s) ppm. IR
5-exo-(2-Methoxyphenyl)-6-exo-(2-phenylethynyl)-7-oxabenzonor-
bornene (4k): Yield: 396 mg (65 %), m.p. 127–129 °C. 1H NMR
(200 MHz, CDCl3): δ = 3.31 (d, J = 8.5 Hz, 1 H), 3.69 (d, J =
(neat): 3060.9, 2929.7, 1603.0, 1459.3, 1377.2, 1263.6, 758.6,
8.5 Hz, 1 H), 3.74 (s, 3 H), 5.55 (s, 1 H), 5.64 (s, 1 H), 6.83–6.93
700.0 cm–1. HRMS: calcd. for C22H22O 302.1671; found 302.1671.
(m, 3 H), 7.00–7.43 (m, 9 H), 7.66 (d, J = 6.9 Hz, 1 H) ppm. 13C
5-exo-(3-Methoxyprop-1-ynyl)-6-exo-phenyl-7-oxabenzonorbornene
(4f): Yield: 382 mg (76%). H NMR (200 MHz, CDCl3): δ = 2.88
NMR (50 MHz, CDCl3): δ = 39.8 (d), 43.2 (d), 55.3 (q), 83.4 (d),
84.4 (s). 84.7 (d), 89.5 (s), 109.9 (d), 119.1 (d), 119.5 (d), 123.5 (s),
126.8 (d), 127.1 (d), 127.3 (d), 127.4 (d), 127.7 (d), 128.3 (d), 129.6
(d), 131.3 (s), 145.2 (s), 146.1 (s), 157.5 (s) ppm. IR (KBr): 3053.5,
2920.9, 1595.3, 1465.7, 1243.2, 751.9, 695.0 cm–1. HRMS: calcd.
for C25H20O2 352.1463; found 352.1461. C25H20O2 (352.43): calcd.
C 85.20, H 5.72; found C 85.25, H 5.69.
1
(s, 3 H), 3.00 (dt, J = 8.6, 1.6 Hz, 1 H), 3.08 (d, J = 8.6 Hz, 1 H),
3.68–3.72 (m, 2 H), 5.38 (s, 2 H), 7.08–7.32 (m, 9 H) ppm. 13C
NMR (50 MHz, CDCl3): 40.0 (d), 50.3 (d), 56.7 (q), 59.5 (t), 80.9
(s), 84.6 (d). 85.0 (d), 86.1 (s), 118.9 (d), 119.4 (d), 126.4 (d), 126.8
(d), 127.1 (d), 127.7 (d), 128.9 (d), 140.7 (s), 144.8 (s), 145.6 (s)
ppm. IR (neat): 3060.5, 2927.8, 1602.1, 1459.9, 1357.2, 1095.4,
750.3, 700.7 cm–1. HRMS: calcd. for C20H18O2 290.1307; found
290.1305.
5-exo-(4-Acetylphenyl)-6-exo-(2-phenylethynyl)-7-oxabenzonor-
bornene (4l): Yield: 441 mg (70 %), m.p. 150–151 °C. 1H NMR
(200 MHz, CDCl3): δ = 2.60 (s, 3 H), 3.32 (s, 2 H), 5.53 (s, 1 H),
5.60 (s, 1 H), 6.89–6.96 (m, 2 H), 7.08–7.44 (m, 7 H), 7.56 (d, J =
8.2 Hz, 2 H), 7.95 (d, J = 8.2 Hz, 2 H) ppm. 13C NMR (50 MHz,
5-exo-(2-Phenylethynyl)-6-exo-p-tolyl-7-oxabenzonorbornene (4g):
Yield: 425 mg (73 %), m.p. 107–109 °C. 1H NMR (200 MHz,
CDCl3): δ = 2.22 (s, 3 H), 3.08 (s, 2 H), 5.35 (s, 1 H), 5.41 (s, 1 H), CDCl3): δ = 26.6 (q), 40.8 (d), 50.7 (d), 84.7 (d), 84.8 (d). 85.9 (s),
6.80–6.89 (m, 2 H), 6.96–7.26 (m, 11 H) ppm. 13C NMR (50 MHz,
CDCl3): δ = 20.9 (q), 40.6 (d), 50.3 (d), 84.5 (d), 85.1 (d). 85.5 (s),
89.6 (s), 119.0 (d), 119.5 (d), 123.4 (s), 126.8 (d), 127.1 (d), 127.4
88.8 (s), 119.2 (d), 119.6 (d), 123.0 (s), 127.2 (d), 127.4 (d), 127.7
(d), 127.9 (d), 128.0 (d), 129.4 (d), 131.1 (d), 135.6 (s), 144.9 (s),
145.3 (s), 146.7 (s), 197.9 (s) ppm. IR (KBr): 3002.5, 2931.4, 1671.2,
(d), 127.8 (d), 128.4 (d), 128.9 (d), 131.3 (d), 135.9 (s), 137.8 (s), 1606.0, 1488.8, 1272.6, 849.8, 757.4, 691.7 cm–1. HRMS: calcd. for
144.9 (s), 145.8 (s) ppm. IR (KBr): 3011.5, 2936.1, 1596.1, 1461.5,
C26H20O2 364.1463; found 364.1465. C26H20O2 (364.44): calcd. C
85.69, H 5.53; found C 85.80, H 5.55.
1194.0, 848.8, 759.2, 691.6 cm–1. HRMS: calcd. for C25H20
O
Eur. J. Org. Chem. 2008, 485–491
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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489

C.-J. Kuo, S.-J. Cheng, S.-T. Chang, C.-H. Liu
FULL PAPER
5-exo-(4-Nitrophenyl)-6-exo-(2-phenylethynyl)-7-oxabenzonorbor-
nene (4m): Yield: 252 mg (40 %), m.p. 215–216 °C. 1H NMR
(200 MHz, CDCl3): δ = 3.35 (s, 2 H), 5.50 (s, 1 H), 5.61 (s, 1 H),
= 7.2 Hz, 3 H), 1.92–2.07 (m, 1 H), 2.80 (d, J = 8.1 Hz, 2 H), 4.92
(s, 1 H), 5.34 (s, 1 H),7.04–7.24 (m, 6 H), 7.32–7.40 (m, 2 H) ppm.
13C NMR (50 MHz, CDCl3): δ = 17.5 (q), 38.1 (d), 38.3 (d), 83.8
6.90–6.98 (m, 2 H), 7.11–7.44 (m, 7 H), 7.64 (d, J = 8.7 Hz, 2 H), (s), 85.3 (d), 85.4 (d), 89.2 (s), 119.1 (d), 119.2 (d), 123.7 (s), 126.7
8.20 (d, J = 8.7 Hz, 2 H) ppm. 13C NMR (50 MHz, CDCl3): δ = (d), 127.0 (d), 127.7 (d), 128.1 (d), 131.6 (d), 144.6 (s), 145.6 (s)
40.9 (d), 50.7 (d), 84.9 (d), 86.4 (s), 88.3 (s), 119.3 (d), 119.7 (d),
122.7 (s), 122.9 (d), 127.4 (d), 127.6 (d), 128.0 (d), 128.2 (d), 130.1
ppm. IR (neat):3046.1, 2925.6, 1598.1, 1461.8, 1377.5, 1153.8,
752.8, 691.3 cm–1. HRMS: calcd. for C19H16O 260.1201; found
(d), 131.1 (d), 144.8 (s), 145.0 (s), 146.8 (s), 148.9 (s) ppm. IR 260.1199.
(KBr): 3064.5, 1596.6, 1506.0, 1489.3, 1342.1, 847.3, 755.0,
5-exo-(2-Phenylethynyl)-6-exo-(2-phenylethynyl)-7-oxabenzonorbor-
691.9 cm–1. HRMS: calcd. for C24H17NO3 367.1208; found
367.1205. C24H17NO3 (367.40): calcd. C 78.46, H 4.66, N 3.81;
found C 78.07, H 4.69, N 3.78.
nene (4s): Yield: 270 mg (45 %), m.p. 160–162 °C. 1H NMR
(200 MHz, CDCl3): δ = 3.16 (s, 2 H), 5.60 (s, 2 H), 7.18–7.30 (m,
8 H), 7.30–7.38 (m, 2 H), 7.38–7.75 (m, 4 H) ppm. 13C NMR
(50 MHz, CDCl3): δ = 39.5 (d), 85.0 (d), 88.6 (s), 119.6 (d), 123.5
(s), 127.5 (d), 127.9 (d), 128.1 (d), 131.8 (d), 144.3 (s) ppm. IR
(KBr): 3059.1, 1597.6, 1490.1, 1227.9, 758.1, 691.6 cm–1. HRMS:
calcd. for C26H18O 346.1358; found 346.1359. C26H18O (346.42):
calcd. C 90.14, H 5.24; found C 89.77, H 5.21.
5-exo-(2-Nitrophenyl)-6-exo-(2-phenylethynyl)-7-oxabenzonorbor-
nene (4n): Yield: 102 mg (16 %), m.p. 155–156 °C. 1H NMR
(200 MHz, CDCl3): δ = 3.53 (d, J = 8.3 Hz, 1 H), 3.73 (d, J =
8.3 Hz, 1 H), 5.50 (s, 1 H), 5.60 (s, 1 H), 6.76–6.85 (m, 2 H), 6.99–
7.39 (m, 8 H), 7.58 (t, J = 7.7 Hz, 1 H), 7.84 (dd, J = 8.1, 1.1 Hz,
1 H), 7.94 (d, J = 8.0 Hz, 1 H) ppm. 13C NMR (50 MHz, CDCl3):
δ = 41.4 (d), 46.6 (d), 83.8 (d), 84.6 (d), 85.0 (s), 88.5 (s), 119.3 (d),
119.7 (d), 123.0 (s), 124.0 (d), 127.3 (d), 127.4 (d), 127.5 (d), 127.7
(d), 127.9 (d) 130.3 (d), 131.2 (d), 132.7 (d), 136.6 (s), 145.0 (s),
145.1 (s), 145.0 (s) ppm. IR (KBr): 3086.5, 1523.3, 1347.2, 1263.2,
755.6, 691.8 cm–1. HRMS: calcd. for C24H17NO3 367.1208; found
367.1206. C24H17NO3 (367.40): calcd. C 78.46, H 4.66, N 3.81;
found C 78.17, H 4.68, N 3.77.
1,2,3,4-Tetrahydro-6,7-dimethoxy-1,4-epoxynaphthalene-2-exo-
phenyl-3-exo-(2-phenylethynyl) (4t): Yield: 529 mg (80%), m.p. 150–
1
153 °C. H NMR (200 MHz, CDCl3): δ = 3.21 (s, 2 H), 3.88 (s, 3
H), 3.90 (s, 3 H), 5.47 (s, 1 H), 5.52 (s, 1 H), 6.89–7.01 (m, 4 H),
7.11–7.49 (m, 8 H) ppm. 13C NMR (50 MHz, CDCl3): δ = 41.2
(d), 51.3 (d), 56.3 (q), 85.0 (d), 85.5 (d), 89.6 (s), 103.9 (d), 104.4
(d), 123.4 (s), 126.6 (d), 127.5 (d), 127.9 (d), 129.2 (d), 131.4 (d),
137.4 (s), 138.3 (s), 141.1 (s), 148.3 (s), 148.5 (s) ppm. IR (KBr):
3062.0, 2998.8, 1597.8, 1490.5, 1307.7, 1218.9, 1090.3, 757.5,
693.4 cm–1. HRMS: calcd. for C26H22O3 382.1569; found 382.1570.
C26H22O3 (382.45): calcd. C 81.65, H 5.80; found C 81.46, H 5.79.
5-exo-(Naphthalen-1-yl)-6-exo-(2-phenylethynyl)-7-oxabenzonorbor-
nene (4o): Yield: 322 mg (50 %), m.p. 226–228 °C. 1H NMR
(200 MHz, CDCl3): δ = 3.52 (d, J = 8.5 Hz, 1 H), 4.02 (d, J =
8.5 Hz, 1 H), 5.64 (s, 1 H), 5.87 (s, 1 H), 6.47–6.57 (m, 2 H), 6.94–
7.08 (m, 3 H), 7.22–7.62 (m, 7 H), 7.76–7.95 (m, 4 H) ppm. 13C
NMR (50 MHz, CDCl3): δ = 40.4 (d), 46.0 (d), 84.0 (d), 84.7 (s),
85.0 (d), 88.7 (s), 119.3 (d), 119.7 (d), 123.0 (s), 123.3 (d), 124.9
(d), 125.2 (d), 125.5 (d), 125.8 (d), 127.0 (d), 127.1 (d), 127.3 (d),
127.4 (d), 127.6 (d, 2 C), 128.7 (d), 131.1 (d, 2 C), 132.8 (s), 133.5
(s), 137.0 (s), 145.3 (s), 146.1 (s) ppm. IR (KBr): 3043.8, 1596.8,
1,2,3,4-Tetrahydro-1,4-epoxytriphenylene-2-exo-phenyl-3-exo-(2-
phenylethynyl) (4u): Yield: 526 mg (72%), m.p. 209–211 °C. 1H
NMR (200 MHz, CDCl3): δ = 3.20 (s, 2 H), 6.05 (s, 1 H), 6.08 (s,
1 H), 6.89–6.98 (m, 2 H), 7.07–7.16 (m, 3 H), 7.24–7.38 (m, 4 H),
7.42–7.50 (m, 2 H), 7.56–7.69 (m, 4 H), 7.81–7.88 (m, 1 H), 7.96–
8.06 (m, 1 H), 8.65–8.75 (m, 1 H) ppm. 13C NMR (50 MHz,
CDCl3): δ = 40.8 (d), 50.9 (d), 84.4 (d), 84.8 (d), 85.5 (s), 89.7 (s),
123.4 (s), 123.7 (d), 124.4 (d), 125.4 (s), 125.7 (s), 126.60 (d), 126.7
(d), 126.8 (d), 127.2 (d), 127.60 (d), 127.9 (d), 128.0 (d), 129.4 (d),
130.3 (s), 130.4 (s), 131.4 (d), 140.5 (s), 141.1 (s), 141.4 (s) ppm. IR
(KBr): 3034.0, 1592.1, 1488.1, 1213.9, 752.4, 693.7 cm–1. HRMS:
calcd. for C32H22O 422.1671; found 422.1670. C32H22O (422.52):
calcd. C 90.97, H 5.25; found C 90.67, H 5.13.
1459.6, 1153.7, 745.0, 689.1 cm–1. HRMS: calcd. for C28H20
372.1514; found 372.1512.
O
5-exo-(2-Phenylethynyl)-6-exo-(2-thienyl)-7-oxabenzonorbornene
1
(4p): Yield: 318 mg (56%), m.p. 127–128 °C. H NMR (200 MHz,
CDCl3): δ = 3.17 (d, J = 8.2 Hz, 1 H), 3.54 (d, J = 8.2 Hz, 1 H),
5.48 (s, 1 H), 5.51 (s, 1 H), 6.79–7.7.51 (m, 12 H) ppm. 13C NMR
(50 MHz, CDCl3): δ = 41.1 (d), 46.3 (d), 85.0 (d), 85.3 (s), 85.8 (d),
88.6 (s), 119.4 (d), 119.5 (d), 123.3 (s), 124.3 (d), 126.1 (d), 126.2
(d), 127.3 (d), 127.6 (d), 127.9 (d) 131.4 (d), 143.8 (s), 144.7 (s),
144.9 (s) ppm. IR (KBr): 3004.0, 1597.7, 1461.7, 1265.6, 760.4,
692.4 cm–1. HRMS: calcd. for C22H16OS 328.0922; found 328.0921.
C22H16OS (328.43): calcd. C 80.45, H 4.91, S 9.76; found C 80.22,
H 4.66, S 10.08.
General Procedure for the Deoxyaromatization Reaction: In a typi-
cal procedure, a round-bottom flask containing compound 4
(0.55 mmol) was purged with nitrogen three times. To the flask was
added sequentially CH2Cl2 (5 mL) and BF3·OEt2 (1.10 mmol). The
solution was then stirred at room temperature for 1 h. After fil-
tration through Celite, the filtrate was concentrated and then sepa-
rated on a silica gel column (hexane/ethyl acetate) to give desired
product 5.
5-exo-(2-Phenylethynyl)-6-exo-(3-oxocyclohex-1-enyl)-7-oxabenzo-
1
norbornene (4q): Yield: 165 mg (28%), m.p. 179–180 °C. H NMR
(200 MHz, CDCl3): δ = 1.91–2.08 (m, 2 H), 2.31–2.54 (m, 3 H),
2.60–2.75 (m, 1 H), 2.80 (d, J = 8.7 Hz, 1 H), 3.23 (d, J = 8.7 Hz,
1 H), 5.49 (s, 1 H), 5.53 (s, 1 H), 6.16 (s, 1 H), 7.17–7.43 (m, 9 H)
ppm. 13C NMR (50 MHz, CDCl3): δ = 22.6 (t), 29.5 (t), 37.6 (t),
39.6 (d), 52.3 (d), 81.9 (d), 84.3 (s), 84.8 (d), 88.1 (s), 119.3 (d),
119.6 (d), 123.0 (s), 127.3 (d), 127.5 (d), 128.0 (d), 128.1 (d), 128.3
(d), 131.5 (d), 144.7 (s), 144.9 (s), 164.5 (s), 199.7 (s) ppm. IR
(KBr): 3084.7, 1665.8, 1598.3, 1490.5, 1460.8, 1256.3, 760.9,
692.5 cm–1. HRMS: calcd. for C24H20O2 340.1463; found 340.1465.
C24H20O2 (340.41): calcd. C 84.68, H 5.92; found C 84.60, H 5.94.
5-Phenyltetraphene (5a): Yield: 100 mg (60%), m.p. 133–135 °C. 1H
NMR (200 MHz, CDCl3): δ = 7.41–7.62 (m, 8 H), 7.68 (dd, J =
7.9, 1.2 Hz, 1 H), 7.73 (s, 1 H), 7.87 (dd, J = 7.9, 1.0 Hz, 1 H),
7.99–8.19 (m, 2 H), 8.36 (s, 1 H), 8.92 (d, J = 8.0 Hz, 1 H), 9.20
(s, 1 H) ppm. 13C NMR (50 MHz, CDCl3): δ = 121.4 (d), 123.2
(d), 125.7 (d), 125.8 (d), 126.7 (d), 126.8 (d), 126.9 (d), 127.1 (d),
127.4 (d), 127.7 (d), 127.9 (d), 128.3 (d, 2 C), 128.5 (d), 128.6 (s),
129.9 (d, 2 C), 130.2 (s), 130.9 (s), 131.4 (s), 131.9 (s), 132.2 (s),
138.7 (s), 140.7 (s) ppm. IR (KBr): 3053.5, 1601.2, 1471.2, 903.1,
741.7, 700.5 cm–1. HRMS: calcd. for C24H16 304.1252; found
304.1249. C24H16 (304.38): calcd. C 94.70, H 5.30; found C 94.78,
H 5.30.
5-exo-(2-Phenylethynyl)-6-exo-methyl-7-oxabenzonorbornene (4r):
1
Yield: 162 mg (36%). H NMR (200 MHz, CDCl3): δ = 1.32 (d, J
490
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 485–491

An Efficient Route to Polyaromatic Hydrocarbons
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3-Methyl-5-phenyltetraphene (5b): Yield: 137 mg (78%), m.p. 160–
161 °C. H NMR (200 MHz, CDCl3): δ = 2.41 (s, 3 H), 7.35–7.60
1
(m, 9 H), 7.63 (s, 1 H), 7.92–8.11 (m, 2 H), 8.27 (s, 1 H), 8.74 (d,
J = 8.4 Hz, 1 H), 9.08 (s, 1 H) ppm. 13C NMR (50 MHz, [D8]-
THF): δ = 21.8 (q), 122.1 (d), 124.4 (d), 126.5 (d, 2 C), 127.7 (d),
127.7 (d), 128.3 (d), 128.6 (d), 128.8 (d), 129.1 (d), 129.3 (d, 2 C),
129.4 (d), 129.9 (s), 130.9 (d, 2 C), 131.2 (s) 132.5 (s), 133.3 (s),
133.4 (s), 137.6 (s), 139.8 (s), 142.1 (s) ppm. IR (KBr): 3051.9,
2945.8, 1620.2, 1467.2, 902.1, 739.9, 700.6 cm–1. HRMS: calcd. for
C25H18 318.1409; found 318.1410.
3-Methoxy-5-phenyltetraphene (5c): Yield: 153 mg (83%), m.p. 133–
1
134 °C. H NMR (200 MHz, CDCl3): δ = 3.81 (s, 3 H), 7.26–7.35
(m, 2 H), 7.44–7.63 (m, 7 H), 7.72 (s, 1 H), 7.98–8.15 (m, 2 H),
8.33 (s, 1 H), 8.82 (d, J = 9.7 Hz, 1 H), 9.07 (s, 1 H) ppm. 13C
NMR (50 MHz, [D8]THF): δ = 55.5 (q), 109.9 (d), 116.4 (d), 121.5
(d), 125.9 (d, 2 C), 126.2 (d), 126.5 (d), 127.8 (d), 128.4 (d), 128.6
(d), 129.2 (d), 129.4 (d, 2 C), 123.0 (s), 130.7 (d, 2 C), 132.9 (s)
133.5 (s), 133.8 (s), 139.5 (s), 142.0 (s), 160.0 (s) ppm. IR (KBr):
3053.6, 2924.1, 1609.1, 1463.7, 1219.1, 741.7, 701.0 cm–1. HRMS:
calcd. for C25H18O 334.1358; found 334.1356. C25H18O (334.41):
calcd. C 89.79, H 5.43; found C 89.60, H 5.23.
1-(5-Phenyltetraphen-3-yl)ethanone (5d): Yield: 124 mg (65%), m.p.
1
131–132 °C. H NMR (200 MHz, CDCl3): δ = 2.61 (s, 3 H), 7.38–
7.62 (m, 7 H), 7.73 (s, 1 H), 7.92–8.13 (m, 2 H), 8.36 (dd, J = 8.6,
1.9 Hz, 1 H), 8.40 (s, 1 H), 8.46–8.52 (m, 1 H), 8.98 (d, J = 8.6 Hz,
1 H), 9.24 (s, 1 H) ppm. 13C NMR (50 MHz, CDCl3): δ = 26.6 (q),
122.6 (d), 123.6 (d), 125.4 (d), 126.0 (d), 126.5 (d), 127.1 (d), 127.7
(d), 127.8 (d), 128.0 (d), 128.5 (d, 2 C), 128.7 (d, 2 C), 129.8 (d, 2
C), 130.5 (s), 131.0 (s), 132.0 (s), 132.7 (s), 134.4 (s), 135.1 (s),
138.6 (s), 140.0 (s), 198.0 (s) ppm. IR (KBr): 3095.4, 2924.6, 1673.8,
1624.5, 1493.6, 1372.4, 742.6, 699.4 cm–1. HRMS: calcd. for
C26H18O 346.1358; found 346.1359. C26H18O (346.42): calcd. C
90.14, H 5.24; found C 90.02, H 5.25.
Acknowledgments
[15] For 4k: cell parameters: a = 16.122(3) Å, b = 11.678(2) Å, c
= 19.930(3) Å]; for 5a: cell parameters: a = 13.615(3) Å, b =
30.332(8) Å, c = 7.689(2) Å. CCDC-656613 and -656614 con-
tain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
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We thank the National Science Council of Republic of China
(NSC-96–2113-M-041–001) for support of this research, and we
thank Professor Sue-Lein Wang (National Tsing Hua University)
for X-ray analysis.
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Received: August 20, 2007
Published Online: November 22, 2007
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