A highly efficient palladacycle catalyst for hydrophenylation of C-, N-, and O-substituted bicyclic alkenes under aerobic condition

Article abstract of DOI:10.1021/jo050491b

A new phosphine-free palladacycle catalyst 4 was prepared from benzyl oxazoline in high yield and fully characterized. With it as catalyst, hydrophenylation reactions of a wide range of bicyclic alkenes, not only norbomene and norborriadiene but also oxa-

Full text of DOI:10.1021/jo050491b

achieved.3 Hydroarylation reaction, similar to the Heck
reaction, also is an useful methodology developed by
Larock and co-workers in 19894 and was employed
successfully in the synthesis of natural products analo-
gous to epibatidine alkaloid.5 However, to the best of our
knowledge, there are only two cases so far using palla-
dacycles as catalysts in hydroarylation reactions and
substrates were limited to norbornene and norborna-
diene.6,7 In our previous studies on the design, synthesis,
and application of ligands in asymmetric catalysis,8 we
found that catalyst with ligands bearing a substituent
at the benzylic position showed higher catalytic
activity.8b,g,k On the basis of these findings, we designed
and synthesized a novel palladacycle, with an oxazoline
moiety and two methyl groups situated at the benzylic
position, and found that it was highly efficient in the
hydrophenylation of a variety of bicyclic alkenes, not only
norbornene and norbornadiene but also oxa- and aza-
bicyclic alkenes, with PhI. Herein we would like to report
our preliminary results on the synthesis, characteriza-
tion, and application of this palladacycle in hydrophen-
ylation reaction.
A Highly Efficient Palladacycle Catalyst
for Hydrophenylation of C-, N-, and
O-Substituted Bicyclic Alkenes under
Aerobic Condition
Ke Yuan,† Ting Ke Zhang,‡ and Xue Long Hou*,†,‡
State Key Laboratory of Organometallic Chemistry and
Shanghai Hong Kong Joint Laboratory in Chemical
Synthesis, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, 354 Fenglin Lu,
Shanghai 200032, China
xlhou@mail.sioc.ac.cn
Received March 11, 2005
The synthesis of palladacycle 4 is as follows (Scheme
1). Compound 19 reacted with SOCl2 followed by treat-
ment with L-valinol to afford amide 2, from which
oxazoline 3 was prepared using the literature proce-
dure.10 The palladacycle 4 was afforded as a yellow
A new phosphine-free palladacycle catalyst 4 was prepared
from benzyl oxazoline in high yield and fully characterized.
With it as catalyst, hydrophenylation reactions of a wide
range of bicyclic alkenes, not only norbornene and norbor-
nadiene but also oxa- and aza-bicyclic alkenes, with iodo-
benzene proceeded smoothly under aerobic condition without
exclusion of water. Up to 1.7 × 106 TON as well as 1.2 ×
105 TOF were achieved.
(3) For some examples, see: (a) Herrmann, W. A.; Brossmer, C.;
Ofele, K.; Reisinger, C. P.; Priermeier, T.; Beller, M.; Fischer, H. Angew.
Chem., Int. Ed. Engl. 1995, 34, 1844. (b) Ohff, M.; Ohff, A.; Boom, M.
E.; Milstein, D. J. Am. Chem. Soc. 1997, 119, 11687. (c) Shaw, B. L.;
Perera, S. D.; Staley, E. A. Chem. Commun. 1998, 1362. (d) Ohff, M.;
Ohff, A.; Milstein, Chem. Commun. 1999, 357. (e) Gruber, A. S.; Zim,
D.; Ebeling, G.; Monteiro, A. L.; Dupont, J. Org. Lett. 2000, 2, 1287.
(f) Wu, Y. J.; Hou, J. J.; Yun, H. Y.; Cui, X. L.; Yuan, Y. J. J. Organomet.
Chem. 2001, 639, 793. (g) Alonso, D. A.; Najera, C.; Pacheco, M. C.
Adv. Synth. Catal. 2002, 344, 172. (h) Iyer, S.; Kulkarni, G. M.;
Ramesh, C. Tetrahedron 2004, 60, 2163. (i) Svennebring, A.; Nilsson,
P. Larhed, M. J. Org. Chem. 2004, 69, 3345. (j) Liang, B.; Dai, M.;
Chen, J. Yang, Z. J. Org. Chem. 2005, 70, 391.
Carbon-carbon bond formations are among the most
important reactions in organic synthesis. A variety of
metal complexes have been used as catalyst in such
transformations.1 Among them, palladacycles have showed
enormous superiority in many respects due to their ready
preparation, air and moisture stability, low loading, and
high efficiency.2 Many palladacycles are efficient Heck-
type reaction catalysts and very high (up to 1010) turnover
numbers (TON, mol product per mol catalyst) are
(4) Larock, R. C.; Johnson, P. L. J. Chem. Soc., Chem. Commun.
1989, 1368.
(5) (a) Kasyan, A.; Wagner, C.; Maier, M. E. Tetrathedron 1998, 54,
8047. (b) Namyslo, J. C.; Kaufmann, D. E. Synlett 1999, 114. (c)
Namyslo, J. C.; Kaufmann, D. E. Synlett 1999, 804.
(6) Brunel, J. M.; Heumann, A.; Buono, G. Angew. Chem., Int. Ed.
2000, 39, 1946.
(7) Bravo, J.; Cativiela, C.; Navarro, R.; Urriolabeitia, E. P. J.
Organomet. Chem. 2002, 650, 157.
(8) (a) Dai, L. X.; Tu, T.; You, S. L.; Deng, W.-P.; Hou, X. L. Acc.
Chem. Res. 2003, 36, 659. (b) Hou, X. L.; Wu, X. W.; Dai, L. X.; Cao, B.
X.; Sun, J.; Chem. Commun. 2000, 1195. (c) Deng, W.-P.; You, S.-L.;
Hou, X.-L.; Dai, L.-X.; Yu, Y.-H.; Xia, W. J. Am. Chem. Soc., 2001,
123, 6508. (d) You, S.-L.; Hou, X.-L.; Dai, L.-X.; Zhu, X.-Z. Org. Lett.
2001, 3, 149. (e) You, S. L.; Zhu, X. Z.; Luo, Y. M.; Hou, X. L.; Dai, L.
X. J. Am. Chem. Soc. 2001, 123, 7471. (f) You, S. L.; Hou, X. L.; Dai,
L. X.; Yu,. H.; Xia, W. J. Org. Chem. 2002, 67, 4684. (g) Wu, H.; Wu,
X. W.; Hou, X. L.; Dai, L. X.; Wang, Q. R. Chin. J. Chem. 2002, 20,
816. (h) Tu, T.; Deng, W.-P.; Hou, X.-L.; Dai, L.-X. Dong, X.-C. Chem.
Eur J. 2003, 9, 3073. (i) Tu, T.; Zhou, Y. G.; Hou, X. L.; Dai, L. X.;
Dong, X. C.; Yu, Y. H.; Sun, J. Organometallics 2003, 22, 125. (j) Tu,
T.; Hou, X. L.; Dai, L. X. Org. Lett. 2003, 5, 3651. (k) Dong, D. X.;
Hou, X. L.; Yuan, K. Tetrahedron: Asymmetry 2004, 15, 2189.
(9) Beak, P.; Kerrick, S. T.; Gallagher, D. J. J. Am. Chem. Soc. 1993,
115, 10628.
† State Key Laboratory of Organometallic Chemistry.
‡ Shanghai Hong Kong Joint Laboratory in Chemical Synthesis.
(1) (a) Meijere, A.; Meyer, F. E. Angew. Chem., Int. Ed. Engl. 1994,
33, 2379. (b) Malloren, J. L.; Fiaud, J. C.; Legros, J.-Y. Handbook of
Palladium-Catalyzed Organic Reaction; Academic Press: San Diego,
1997. (c) Nicolaou, K. C.; Sorensen, E. J. Classics in Total Synthesis;
VCH: Weinheim, 1996. (d) Applied Homogeneous Catalysis with
Organometallic Compounds: A Comprehensive Handbook in Three
Volumes; 2nd ed.; Cornils, B., Herrmann, W. A., Eds.; Wiley: Wein-
heim, 2002. (e) Tsuji, J. Transition Metal Reagents and Catalysts:
Innovations in Organic Synthesis; Wiley: Chichester, 2000.
(2) For some reviews, see: (a) Herrmann, W. A.; Bohm, V. P. W.;
Reisenger, C. P. J. Organomet. Chem. 1999, 576, 23. (b) Dupont, J.;
Pfeiffer, M.; Spencer, J. Eur. J. Inorg. Chem. 2001, 1917. (c) Bedford,
R. B. Chem. Commun. 2003, 1787. (d) Boom, M. E.; Milstein, D. Chem.
Rev. 2003, 103, 1759.
(10) Vorbriiggen, H.; Krolikiewicz, K. Tetrahedron Lett. 1981, 22,
4471.
10.1021/jo050491b CCC: $30.25 © 2005 American Chemical Society
Published on Web 06/25/2005
J. Org. Chem. 2005, 70, 6085-6088
6085

SCHEME 1. Synthesis of palladacycle 4
TABLE 1. Hydrophenylation of Norbornene Catalyzed
by Palladacycle 4a
powder after an oxidative addition reaction of Pd2(dba)3‚
CHCl3 with oxazoline 3. Palladacycle 4 is air stable. The
X-ray diffraction analysis showed that it is a dimer with
a distorted square-planar geometry (Figure 1).
en-
temp time yield
(°C) (h)b (%)c
TOF
(h-1
)
try solvent PhX
4
TON
1
2
3
4
5
6
7
8
toluene PhI 2.5 × 10-3 120 18
20 4 × 103 222
75 1.5 × 104 833
50 1.0 × 104 555
82 1.6 × 104 911
DMF
DMA
NMP
PhI 2.5 × 10-3 120 18
PhI 2.5 × 10-3 120 18
PhI 2.5 × 10-3 120 18
DMSO PhI 2.5 × 10-3 120
1
97 1.9 × 104 1.9 × 104
DMSO PhCl 0.25
DMSO PhBr 0.25
DMSO PhI 0.25
120 24
120 24
0
0
0
15 30
1.25
396
396
65
65
0.5 99 198
0.5 99 198
9d DMSO PhI 0.25
10 DMSO PhI 2.5 × 10-5 120 15
87 1.7 × 106 1.2 × 105
a Reaction conditions: PhX (1 mmol), norbornene (3 mmol),
formic acid (3 mmol), Pr2NEt (4 mmol), solvent (5 mL). b Moni-
i
tored by GC. c Isolated yield. d 2 mL of H2O was added.
FIGURE 1. ORTEP drawing of 4. Hydrogens are omitted for
clarity. Selected bond distances (Å) and angels (deg): Pd-C(1)
1.997(9); Pd-N(1) 2.032(8); Pd-Br 2.4561(12); Pd-Br(A)
2.5948(12); C(1)-Pd-N(1) 85.7(3); C(1)-Pd-Br 93.0(3); N(1)-
Pd-Br 172.3(3); C(1)-Pd-Br(A) 178.6(3); N(1)-Pd-Br(A)
95.2(2); Br-Pd-Br(A) 86.26(5)
10-5 mol %, the yield of product was still good and 1.7 ×
106 TON and 1.2 × 105 TOF were achieved (entry 10,
Table 1).11 All reactions were carried out under aerobic
condition, and the presence of water did not disturb the
reaction. If the water was added to the reaction mixture,
the result was the same as that without water (entry 9
vs entry 8, Table 1). Similar to the results reported by
Navarro, the [R]D values of the products were almost zero
in all cases.7 When the palladacycle monomer produced
in situ by the reaction of palladacycle 4 and PPh3 was
used almost same results were provided.
The high catalytic efficiency of palladacycle 4 encour-
aged us to extend the scope of substrates. Instead of
norbornene, several other bicyclic alkenes including oxa-
and aza-bicyclic alkenes were employed in the hydro-
phenylation reaction (Scheme 2), and the results are
summarized in Table 2.
All reactions proceeded smoothly at 120 °C under
aerobic condition to afford corresponding products in good
to excellent yield. TONs of 104 were afforded for all the
bicyclic alkenes, such as benzonorbornadiene 8 (entry 3,
Table 2), oxo-benzonorbornadiene 9 (entry 4, Table 2),
substituted norbornene 11 and oxo-norbornene 12 (en-
tries 6 and 7, Table 2), except aza-bicyclic alkene 10, for
which 0.25 mol % of catalyst 4 should be used (entry 5,
Table 2) because of its low reactivity.12
With the palladacycle 4 in hand, hydrophenylation
reaction of norbornene was carried out to test its catalytic
efficiency. The reaction of norbornene with halobenzene
proceeded utilizing palladacycle 4 as catalyst in the
presence of iPr2NEt/HCOOH in different solvents under
aerobic condition, and the results are listed in Table 1.
As can be seen from Table 1, in all solvents the reaction
led to corresponding exo-phenylnorbornane as single
product, and DMSO is the best one among the solvents
tested (entry 5, Table 1). Using 0.25 mol % of palladacycle
4 in DMSO, hydrophenylation of norbornene with iodo-
benzene gave rise to the corresponding exo-phenylnor-
bornane in almost quantitative yield (entry 8, Table 1),
whereas that with bromobenzene provided the product
in low yield with very low turnover number and turnover
frequency (TOF, mol product per mol catalyst h-1) (entry
7, Table 1) and no reaction took place with chlorobenzene
(entry 6, Table 1). High catalytic activity of palladacycle
4 is also shown in the reaction. When the amount of
catalyst was decreased from 0.25 mol % to 2.5 × 10-3
mol %, a quantitative yield of product was still delivered
with 1.9 × 104 TON and 1.9 × 104 TOF (entry 5, Table
1). Even when the catalyst loading was lowered to 2.5 ×
(11) Sometimes phenylnorbornane was obtained when the amount
of palladaccycle 4 was 2.5 × 10-7 mol %.
6086 J. Org. Chem., Vol. 70, No. 15, 2005

SCHEME 2. Catalytic Hydroarylation of Bicyclic Alkenes
TABLE 2. Catalytic Hydrophenylation of Different
Bicyclic Alkenes with Palladacycle 4a
Dry CH2Cl2 (10 mL) was then added to the acid chloride. Under
argon, valinol (494 mg, 4.8 mmol) and Et3N (606 mg, 6 mmol)
were dissolved in dry CH2Cl2 (10 mL) and cooled to 0 °C. The
above acid chloride solution was added dropwise over a period
of 0.5 h. The reaction mixture was stirred at 0 °C for 2 h, allowed
to warm to room temperature, and stirred for 6 h. The result
solution was washed with water (10 mL) and dried over MgSO4.
The solvent was removed in vacuo, and the crude product was
purified by flash chromatography (EtOAc/petroleum ether ) 1/2)
to give amide 2 as an oil (1.297 g, 99%): 1H NMR (CDCl3, 300
MHz) δ 7.63 (m, 1H, Ar), 7.53 (m, 1H, Ar), 7.39 (m, 1H, Ar),
7.19 (m, 1H, Ar), 5.28 (d, J ) 4.8 Hz, 1H, NH), 3.72-3.63 (m,
3H, CH and CH2), 2.89 (br, 1H, OH), 1.79 (m, 1H, CH), 0.87 (d,
J ) 6.7 Hz, 3H, Me), 0.80 (d, J ) 6.7 Hz, 3H, Me); 13C NMR
(CDCl3, 75 MHz) δ 177.6, 143.0, 135.0, 129.0, 128.2, 127.9, 124.2,
63.9, 57.9, 48.8, 28.8, 26.9, 26.5, 19.5, 18.6; MS (EI) m/z 328 (M
+ 1+, 100); IR (KBr, cm-1) 3414, 3065, 2961, 1653, 1180, 750.
Anal. Calcd for C15H22BrNO2: C, 54.89; H, 6.76; N, 4.27.
Found: C, 54.45; H, 6.93; N, 4.27.
2-(o-Bromo-benzyl) Oxazoline (3). To a solution of amide
2 (1.246 g, 3.8 mmol) in MeCN (10 mL) were added PPh3 (3.144
g, 12 mmol), Et3N (1.818 g, 18 mmol), and CCl4 (5.39 g, 3.4 mL,
35 mmol). The reaction mixture was stirred for overnight at room
temperature. After completion of the reaction (monitored by
TLC), water (10 mL) was added and the resulting mixture was
extracted with CH2Cl2 (10 mL × 3). The combined organic phase
was dried over MgSO4. The solvent was removed in vacuo, and
the crude product was purified by flash chromatography (EtOAc/
petroleum ether ) 1/6) to give benzyl oxazoline 3 as an oil (1.119
g, 95%): 1H NMR (CDCl3, 300 MHz) δ 7.57 (m, 1H, Ar), 7.44
(m, 1H, Ar), 7.31 (m, 1H, Ar), 7.10 (m, 1H, Ar), 4.23 (m, 1H,
CH), 3.98 (m, 2H, CH2), 1.87 (m, 1H, CH), 1.73 (s, 3H, Me), 1.71
(s, 3H, Me), 0.97 (d, J ) 6.9 Hz, 3H, Me), 0.88 (d, J ) 6.9 Hz,
3H, Me); 13C NMR (CDCl3, 75 MHz) δ 171.7, 143.6, 134.6, 128.2,
127.4, 127.3, 123.8, 72.0, 70.3, 42.4, 32.3, 27.7, 27.2, 19.1, 17.9;
MS (EI) m/z 310 (M + 1+, 1.73), 230 (100); IR (KBr, cm-1) 3063,
2958, 1663, 1244, 755. Anal. Calcd for C15H20BrNO: C, 58.07;
H, 6.50; N, 4.51. Found: C, 57.96; H, 6.80; N, 4.54.
yield
entry substrate
4
t (h)b product (%)c
TON
1
2
3
4
5
6
7
5
2.5 × 10-5
2.5 × 10-3
2.5 × 10-3
2.5 × 10-3
0.25
15
3
6
13
14
15
16
17
18
87
89
93
97
66
82
71
1.7 × 106
1.8 × 104
1.9 × 104
1.9 × 104
132
7
8
9
10
11
12
3
4
4
14
12
2.5 × 10-3
1.6 × 104
2.5 × 10-3
1.4 × 104
a Reaction conditions: PhI (0.5 mmol), bicyclic alkene (1.5
i
mmol), formic acid (1.5 mmol), Pr2NEt (2 mmol), DMSO (5 mL).
The reaction was carried out at 120 °C. b Monitored by GC.
c Isolated yield.
In summary, a new phosphine-free palladacycle has
been synthesized in high yield using simple operations
and fully characterized. The palladacycle is well-defined
and air stable. Its high catalytic activity has been shown
in hydrophenylation reactions of a wide range of bicyclic
alkenes with iodobenzene under aerobic condition, and
exclusion of water is not necessary. Up to 1.7 × 106 TON
and 1.2 × 105 TOF were achieved. This is the first
example of hydrophenylation reaction using palladacycle
as catalyst performed under aerobic condition for a wide
range of bicyclic alkenes. We believe that high efficiency
of catalyst will facilitate the procedure of the reaction,
even make it suitable for industrial scale synthesis.
Applying the palladacycle to other coupling and related
reactions is underway.
Experimental Section
Palladacycle (4). To a solution of benzyl oxazoline 3 (310
mg, 1 mmol) in benzene (15 mL) was added Pd2(dba)3‚CHCl3
(620 mg, 0.6 mmol). The reaction mixture was refluxed for 0.5
h to give a dark green solution. Filtration through Celite and
concentration in vacuo afforded the crude product as a yellow
powder, which was purified by flash chromatography (EtOAc/
PE ) 1/10) to give palladacycle 4 as a yellow powder (400 mg,
96%), a mixture of two geometrical isomers: 1H NMR (CDCl3,
300 MHz) major δ 7.57 (d, J ) 7.6 Hz, 1H, Ar), 6.93-6.79 (m,
3H, Ar), 4.45-4.27 (m, 3H, CH and CH2), 2.40 (s, 3H, Me), 1.62
(s, 3H, Me), 0.88 (d, J ) 7.0 Hz, 3H, Me), 0.69 (d, J ) 7.0 Hz,
3H, Me); minor δ 7.51 (d, J ) 7.9 Hz, 1H, Ar), 6.93-6.79 (m,
3H, Ar), 4.45-4.27 (m, 3H, CH and CH2), 2.49 (s, 3H, Me), 1.64
(s, 3H, Me), 0.86 (d, J ) 7.0 Hz, 3H, Me), 0.62 (d, J ) 7.0 Hz,
3H, Me); 13C NMR (CDCl3, 75 MHz) δ 176.0, 144.1, 143.9, 142.1,
141.6, 138.5, 138.0, 125.4, 123.9, 122.9, 71.3, 70.9, 69.9, 68.6,
43.8, 35.4, 35.3, 30.9, 30.6, 22.6, 18.1, 15.9, 15.4; MS (EI) m/z
415 (1/2M+, 0.31), 230 (100); IR (KBr, cm-1) 3044, 2962, 1648,
General. The commercially available reagents were used
without further purification. The solvents were treated by using
standard methods. 1H NMR spectra were recorded in CDCl3, and
the chemical shifts were referenced to CHCl3 (δ 7.27). IR spectra
were measured in cm-1
.
2-Bromo-R,R-dimethylbenzene acetic acid (1) was pre-
pared using the literature procedure.9 1H NMR (CDCl3, 300
MHz) δ 7.57 (m, 1H, Ar), 7.42 (m, 1H, Ar), 7.32 (m, 1H, Ar),
7.12 (m, 1H, Ar), 1.68 (s, 6H, Me); MS (EI) m/z 244 (M+, 0.83),
163 (100).
Phenylacetamide (2). Bromodimethylbenzene acetic acid 1
(972 mg, 4 mmol) was added to thionyl chloride (8 mL). The
reaction mixture was refluxed 3 h and then concentrated in
vacuo. Dry CH2Cl2 (4 mL) was then added, and the mixture was
concentrated in vacuo to remove any remaining thionyl chloride.
(12) Duan, J.-P.; Cheng, C.-H. Organometallics 1995, 14, 1608.
J. Org. Chem, Vol. 70, No. 15, 2005 6087

1
1253, 732. Anal. Calcd for C15H20BrNOPd: C, 43.24; H, 4.84;
N, 3.36. Found: C, 43.67; H, 4.69; N, 3.26.
Phenyl aza-benzonorbornene (16): white solid; H NMR
(CDCl3, 300 MHz) δ 7.46-7.52 (m, 2H), 7.23-7.38 (m, 5H), 6.82-
6.96 (m, 6H), 5.17 (d, J ) 4.5 Hz, 1H), 4.98 (s, 1H), 2.74-2.80
General Procedure for Hydrophenylation of Bicyclic
Alkenes Catalyzed by Palladacycle 4. The appropriate
amount of catalyst, obtained by successive dilution of an initial
catalyst solution, was introduced into 5 mL of DMSO. To the
stirred solution were added iodobenzene (204 mg, 1 mmol),
(m, 1H), 2.24-2.32 (m, 1H), 2.23 (s, 3H), 1.92-1.98 (m, 1H); 13
C
NMR (CDCl3, 75 MHz) δ 144.0, 143.6, 143.5, 143.0, 135.1, 128.9,
128.8, 128.2, 127.8, 127.1, 126.8, 126.7, 120.5, 120.1, 69.5, 64.2,
46.5, 39.1, 21.6; MS (ESI) m/z 376.3 (M+, 1) 414.3 (M+K 39); IR
(KBr, cm-1) 1334, 1164. Anal. Calcd for C23H21NO2S: C, 73.09;
H, 5.39; N, 3.59. Found: C, 73.57; H, 5.64; N, 3.73.
i
norbornene (282 mg, 3 mmol), Pr2NEt (556 mg, 4 mmol), and
formic acid (138 mg, 3 mmol). The reaction was carried at 120
°C and monitored by GC. After cooling, water (5 mL) was added,
and the mixture was extracted with EtOAc (10 mL × 3). The
combined organic phase was dried over MgSO4, filtered, and
concentrated in vacuo. The product was purified by flash
chromatography (petroleum ether).
Phenyl-bicyclo[2.2.1]heptane-2,3-dicarboxylic acid di-
methyl ester (17):17 colorless oil; 1H NMR (CDCl3, 300 MHz) δ
7.32-7.20 (m, 4H, Ar), 7.16 (m, 1H, Ar), 3.70 (s, 6H, Me), 3.52
(t, J ) 7.8 Hz, 1H, CH), 3.18-3.14 (m, 1H, CH), 2.99 (dd, J )
3.6, 12.0 Hz, 1H, CH), 2.71-2.65 (m, 2H, CH2), 2.17-2.11 (m,
1H, CH), 1.76-1.67 (m, 2H, CH2), 1.39-1.35 (m, 1H, CH); 13C
NMR (CDCl3, 75 MHz) δ 172.9, 172.6, 146.0, 128.1, 127.1, 125.6,
51.5, 51.3, 47.6, 46.3, 45.9, 41.3, 39.9, 37.2, 32.9; MS (EI) m/z
288 (M+, 6.99), 142 (100).
Phenylnorbornane (6):13 colorless oil; 1H NMR (CDCl3, 300
MHz) δ 7.26-7.15 (m, 5H, Ar), 2.74 (m, 1H, CH), 2.36 (s, 2H,
CH2), 1.74-1.27 (m, 8H, CH and CH2); MS (EI) m/z 172 (M+,
47.48), 104 (100).
Phenylnorbornene (13):14 colorless oil; 1H NMR (CDCl3, 300
MHz) δ 7.30-7.28 (m, 4H, Ar), 7.19-7.16 (m, 1H, Ar), 6.26 (dd,
J ) 3.2, 5.5 Hz, 1H, CH), 6.17 (dd, J ) 2.9, 5.5 Hz, 1H, CH),
2.97 (s, 1H, CH2), 2.91 (s, 1H, CH2), 2.72 (m, 1H, CH), 1.74-
1.41 (m, 4H, CH and CH2); 13C NMR (CDCl3, 75 MHz) δ 146.1,
137.3, 137.2, 128.2, 127.6, 125.5, 48.2, 45.7, 43.7, 42.3, 33.6; MS
(EI) m/z 170 (M+, 41.30), 104 (100).
Phenyl-7-oxa-bicyclo[2.2.1]heptane-2,3-dicarboxylic acid
dimethyl ester (18):4 white solid; H NMR (CDCl3, 300 MHz)
1
δ 7.27-7.21 (m, 4H, Ar), 7.18 (m, 1H, Ar), 5.05 (d, J ) 5.3 Hz,
1H, CH), 4.83 (s, 1H, CH), 3.70 (s, 3H, Me), 3.66 (s, 3H, Me),
3.15 (d, J ) 9.4 Hz, 1H, CH), 3.08 (d, J ) 9.4 Hz, 1H, CH), 2.93
(dd, J ) 5.0, 9.0 Hz, 1H, CH), 2.15 (dd, J ) 9.0, 12.9 Hz, 1H,
CH2), 1.89-1.83 (m, 1H, CH2); 13C NMR (CDCl3, 75 MHz) δ
171.5, 171.2, 144.8, 128.5, 127.1, 126.5, 84.3, 78.3, 52.3, 52.1,
51.8, 47.7, 40.8; MS (EI) m/z 290 (M+, 8.87), 129 (100).
Phenyl benzonorbornene (14):15 colorless oil; 1H NMR
(CDCl3, 300 MHz) δ 7.35 (m, 4H, Ar), 7.26-7.23 (m, 3H, Ar),
7.16-7.14 (m, 2H, Ar), 3.43 (s, 2H, CH2), 2.85 (m, 1H, CH), 2.03-
1.82 (m, 4H, CH and CH2); 13C NMR (CDCl3, 75 MHz) δ 148.9,
148.6, 145.8, 128.4, 127.4, 125.8, 125.7, 125.6, 120.8, 120.5, 49.8,
46.6, 45.4, 44.2, 36.2; MS (EI) m/z 220 (M+, 17.67), 116 (100).
Phenyl oxo-benzonorbornene (15):16 white solid; 1H NMR
(CDCl3, 300 MHz) δ 7.40-7.18 (m, 9H, Ar), 5.55 (d, J ) 3.6 Hz,
1H, CH), 5.27 (s, 1H, CH), 2.88 (m, 1H, CH), 2.08-2.06 (m, 2H,
CH2); 13C NMR (CDCl3, 75 MHz) δ 146.0, 145.9, 145.0, 128.5,
127.6, 126.7, 126.6, 126.4, 119.1, 118.8, 85.2, 79.1, 45.8, 38.4;
MS (EI) m/z 222 (M+, 0.65), 118 (100).
Acknowledgment. Financially supported by Na-
tional Natural Science Foundation of China, Major
Basic Research Development Program (Grant no.
G2000077506), Chinese Academy of Sciences, Croucher
Foundation of Hong Kong and Shanghai Committee of
Science and Technology. T.K.Z. gratefully acknowledged
Croucher Foundation of Hong Kong for a Studentship.
Supporting Information Available: X-ray analysis of the
palladacycle 4 (CIF). This material is available free of charge
via the Internet at http://pubs.acs.org.
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