Cationic NHC-Pd (NHC = N-heterocyclic carbene) complex-catalyzed cycloisomerization of dienes

Article abstract of DOI:10.1016/j.tetlet.2007.06.162

A variety of [(NHC)Pd(η³-allyl)]Cl (NHC = N-heterocyclic carbene) involving different allyl groups and NHC ligands were synthesized and employed for the cycloisomerization of 1,6-dienes to form cyclic compounds selectively.

Full text of DOI:10.1016/j.tetlet.2007.06.162

Tetrahedron Letters 48 (2007) 6142–6146
Cationic NHC–Pd (NHC = N-heterocyclic carbene)
complex-catalyzed cycloisomerization of dienes
a
b
a
b
b
Young-Jin Song, Il Gu Jung, Harim Lee, Young Tak Lee, Young Keun Chung
a,
*
and Hye-Young Jang
a
Division of Energy Systems Research, Ajou University, Suwon 442-749, Republic of Korea
Intelligent Textile System Research Center, and Department of Chemistry, College of Natural Sciences,
Seoul National University, Seoul 151-747, Republic of Korea
b
Received 15 June 2007; revised 22 June 2007; accepted 26 June 2007
Available online 5 July 2007
3
Abstract—A variety of [(NHC)Pd(g -allyl)]Cl (NHC = N-heterocyclic carbene) involving different allyl groups and NHC ligands
were synthesized and employed for the cycloisomerization of 1,6-dienes to form cyclic compounds selectively.
Ó 2007 Elsevier Ltd. All rights reserved.
Since carbocycles and heterocycles are frequently found
to be a core structure of biologically active materials,
Me
Me
Me
Me
1
MLn
X
X
+
X
+
X
M = Rh, Ni, Ru, Pd
enormous effort has been devoted to the construction
of carbocycles and heterocycles with the simple and easy
way. One of the convenient ways is the transition metal
Me
X = O, NR, C(CO2R)2
a
b
c
2
catalyzed cyclization of enynes, diynes, or dienes. In the
Scheme 1. Cycloisomerization of 1,6-dienes.
case of dienes among the other derivatives, their lower
complexation ability with the transition metal complex
induces the poor selectivity and yield in the cycloisomer-
ization. Therefore, many research groups have studied
to enhance the reactivity of the catalytic system and
a catalyst for the diene cycloisomerization due to the ease
of modifying palladium complexes and their good reac-
tivity toward this reaction. As for an attempt to improve
the regioselectivity and the reaction rate, Widenhoefer
presents that two different cationic Pd complexes [(g -
9
3
4
expand the substrate scope. Electrophilic Sc, Ti, and
5
3
Zr complexes were found to be good for the conversion
+
À
of dienes to cyclic compounds. However, the oxophilicity
of these metal complexes toward the substrates, water,
and air confines the substrate scope and demands vigor-
ously anhydrous and anaerobic reaction conditions. On
C H )Pd(PCy ) (OEt )] [BAr ] [Ar = 3,5-C H (CF ) ]
3 5 3 2 4 6 3 3 2
+
À
and [(phen)Pd(Me)(CH CN)] [BAr ] [Ar = 3,5-C H -
3
4
6
3
(CF ) ], [phen = phenanthroline] catalyze the diene
3
2
cycloisomerization to afford corresponding cyclized
products b and c in good yields with excellent selectivi-
ties, respectively. According to Widenhoefer’s report, it
is speculated that the key factors affecting the reaction
rate and the selectivity might be ligands around the metal
center as well as the cationic character of the palladium
Despite of recent results, the modifica-
tion of ligand in cationic palladium complexes is not well
established yet. In this account, we now report new cat-
6
the other hand, late transition metal complexes (Rh,
7
8
9
10
Ru, Ni, Pd, and Pt ) catalyze the diene cycloisomer-
ization under less vigorous conditions. As shown in
Scheme 1, late transition metal complexes can catalyze
the cycloisomerization of dienes to afford three prod-
ucts. The ratio of three cyclized products depends on
the reaction conditions as well as catalysts.
2
f,9c,d–g
complex.
3
Since recent research focuses on improving the reaction
efficiency and controlling regioselectivity and stereoselec-
tivity, a range of palladium complexes have been used as
alytic systems involving various [(NHC)Pd(g -allyl)]Cl
(NHC = N-heterocyclic carbene) for the regioselective
formation of type a product (Scheme 1).
One of the noticeable properties of N-heterocyclic carb-
enes (NHCs) is the r-donating power rendering different
*
0
Corresponding author. E-mail: hyjang2@ajou.ac.kr
040-4039/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2007.06.162

Y.-J. Song et al. / Tetrahedron Letters 48 (2007) 6142–6146
6143
Known complex A, B, C
i
i
-Pr
i
-Pr
i
i
-Pr
i-Pr
i
-Pr
i-Pr
N
N
N
N
N
N
-Pr Pd
i
-Pr
-Pr Pd
i-Pr
Pd
i-Pr
i-Pr
Cl
Cl
Cl
Me
Ph
A
B
C
Synthesis of complex D, E, F
i
i
-Pr
i-Pr
i
-Pr
i-Pr
Cl-
Ph Ph
N
N
Cl
t
N
KO Bu
N
+
R
Pd Pd
Cl
R
Pd
-Pr
i-Pr
THF
Cl
Ph
i
-Pr
i-Pr
Ph Ph
R
Ph
D (R = H), E (R = Me)
Me
Me
Me
Ph
Cl
Pd Pd
Me
Me
Cl-
Ph
Br
N
N
Br
t
KO Bu
N
N
Me
+
Me
Pd
Me
THF
Br
Br
Cl
Cl
Ph
Me
Me
Ph Ph
Me
Ph
F
3
Scheme 2. [(NHC)Pd(g -allyl)]Cl complexes utilized in the cycloisomerization of dienes.
catalytic behavior of metal complexes in homogeneous
yield and the reaction time (Table 1, entries 1–5). To
examine the electronic effect of NHC ligands, complex
F possessing the bromine substituted NHC ligand was
used as a catalyst, rendering shorter reaction time but
slightly diminished yield (Table 1, entry 9).
1
1,12
catalytic transformations.
Pd(g -allyl) A–F complexes possessing different allyl
Accordingly, six (NHC)-
3
groups and N-heterocyclic carbenes are synthesized
1
3
and used for the cycloisomerization. Complexes A,
1
4
14
B, and C, are known. The synthesis of complexes
D, E, and F17 is described in Scheme 2. The reaction
1
5
16
Based on the results of entries 1–5, and 9 in Table 1, it is
noticed that complex B, C, and E catalyzed-cycloisomer-
izations show good conversion within 30 or 60 min. In
further studies, the complex E was chosen as a catalyst
for the cyclization. To increase the yield of this reaction,
different silver complexes and lithium complexes were
tested to form cationic NHC–Pd complexes. As indi-
cated in entry 6 of Table 1, the reaction involving
complex E and AgClO4 provides the product in
diminished yield (44%). In the case of the reaction using
Li[B(C F ) ], no product was formed even with
3
of [Pd(g -allyl)Cl] complex with the carbene ligand
generated in situ from the imidazolium salt and KO Bu
2
t
was performed in THF at ambient temperature. Result-
3
ing [(NHC)Pd(g -allyl)]Cl complexes are exposed to the
suitable reaction conditions for the cycloisomerization.
To perform an efficient and selective cycloisomerizaiton
3
of 1,6-dienes, [(NHC)Pd(g -allyl)]Cl complexes and sil-
ver additives (e.g., AgSbF and AgClO ) were mixed
6
4
prior to the addition of the diene assuming that highly
reactive cationic NHC–Pd complexes were required for
this process. In the absence of silver additives, the cyc-
lized product was not detected.
6
5 4
extended reaction time (Table 1, entry 7). In this case,
changing solvents did not increase the yield (Table 1,
entry 8). Thus, entry 5 of Table 1 was chosen as stan-
dard reaction conditions, which were subjected to differ-
ent substrate systems.
Upon the addition of substrate 1 to the dichloromethane
(
CH Cl ) solution of cationic NHC–Pd complexes, only
2 2
cyclized product 1a was observed along with the small
amount of uncyclized product 1d (Table 1). Neither
product 1b nor 1c was detected under our reaction con-
ditions. This result indicates that NHC and allyl
ligands on the palladium center might control the reac-
tivity of the catalyst to form product 1a, selectively. Dif-
ferent allyl moieties on the palladium center affect the
Substrate 2 possessing a methyl substituted olefin under-
goes the cyclization to provide the desired product in
1
8
19
moderate yield. Using naphthalene sulfonyl group
instead of p-toluene sulfonyl group in the diene sub-
strate, cyclized product 3a was obtained in good yield
2
0
(Table 2). In addition to nitrogen tethered substrates,

6144
Y.-J. Song et al. / Tetrahedron Letters 48 (2007) 6142–6146
3
+
Table 1. Cycloisomerization of substrate 1 catalyzed by cationic [(NHC)Pd(g -allyl)] complexes
Me
Me
Me
Me
Me
PdLn (5 mol%)
TsN
TsN
+
TsN
+
TsN
+ TsN
solvent
r.t.
Me
Me
1
1a
1b
1c
1d
Entry
PdLn
Additives
Time (min)
Solvent
Yield (1a) (%)
1
2
3
4
5
6
7
8
9
A
B
C
D
E
E
E
E
F
AgSbF
AgSbF
AgSbF
AgSbF
AgSbF
AgClO
6
6
6
6
6
4
(5 mol %)
(5 mol %)
(5 mol %)
(5 mol %)
(5 mol %)
(5 mol %)
180
30
60
180
30
60
60
60
15
CH
CH
CH
CH
CH
CH
CH
2
2
2
2
2
2
2
Cl
Cl
Cl
Cl
Cl
Cl
Cl
2
2
2
2
2
2
2
56
74
73
66
70
44
a
Li[B(C
Li[B(C
6
F
F
5
)
)
4
4
] (10 mol %)
] (10 mol %)
—
—
a
6
5
Chlorobenzene
CH Cl
AgSbF
6
(5 mol %)
2
2
64
a
Product 1a was not observed.
Table 2. Cycloisomerization of diene substrates catalyzed by complex E/AgSbF
6
Entry
Substrate
Product
Yield (%)
70
O
O
S N
O
S N
O
1
Me
Me
1
1a
O
O
S N
O
2
S N
O
49
2
2a
O
O
S N
S N
3
72
O
O
Me
3
3a
The premixed solution of AgSbF
6
(5 mol %) and Pd complex E (5 mol %) in dichloromethane (0.1 M) was added to each substrate at room
temperature. The reaction was run at room temperature until the starting material was consumed.
carbon and oxygen tethered substrates were tested.
Unfortunately, under our reaction conditions carbon
tethered substrates did not react and were recovered at
the end of the reaction. In the case of oxygen tethered
substrate, starting materials were decomposed during
the reaction (Scheme 3). Based on the unsuccessful
results, one can speculate that the basicity of the hetero-
atom in the tether might be critical to perform the
As illustrated in Scheme 4, the proposed catalytic cycle
begins with the formation of a cationic palladium com-
9
g
plex A. Subsequently, the palladium hydride complex
can be formed through the coupling reaction of the allyl
moiety and dienes, followed by b-hydride elimination
2
1
as reported by Keim. Once the palladium hydride
complex (LnPdH) is generated, substrate 1 reacts with
LnPdH through migratory insertion to afford the hydro-
metalated intermediate IA, followed by C–C bond
formation. Intermediate IIA undergoes b-hydride elimi-
efficient cycloisomerization catalyzed by cationic
3
(
NHC)Pd(g -allyl) complexes.
O
BzO
BzO
BnO
BnO
PMB
O
PMB=
MeO
Bz =
Bn=
Ph
Ph
Scheme 3. Unsuccessful substrates under the standard cycloisomerization conditions.

Y.-J. Song et al. / Tetrahedron Letters 48 (2007) 6142–6146
6145
References and notes
H
TsN
TsN
PdLn
1. (a) Trost, B. M. Chem. Soc. Rev. 1982, 11, 141; (b)
Hudlicky, T.; Price, J. D. Chem. Rev. 1989, 89, 1467.
2
. Selected review articles related to the transition metal
catalyzed cyclizations. (a) Trost, B. M. Acc. Chem. Res.
1
IA
1
990, 23, 34; (b) Broene, R. D.; Buchwald, S. In
H
Comprehensive Organometallic Chemistry; Hegedus, L.
S., Ed.; Permagon: London, 1995; Vol. 12, p 323; (c)
Ojima, I.; Tzamarioudaki, M.; Li, Z.; Donovan, R. J.
Chem. Rev. 1996, 96, 635; (d) Trost, B. M.; Krische, M. J.
Synlett 1998, 1; (e) Molander, G. A.; Romero, A. C.
Chem. Rev. 2002, 102, 2161; (f) Widenhoefer, R. A. Acc.
Chem. Res. 2002, 35, 905; (g) Ikeda, S.-I. Angew. Chem.,
Int. Ed. 2003, 42, 5120; (h) Lloyd-Jones, G. C. Org.
Biomol. Chem. 2003, 1, 215; (i) Jang, H.-Y.; Krische, M. J.
Acc. Chem. Res. 2004, 37, 653.
TsN
[
LnPdH]
[
LnPd]
A
H
PdLn
IIA
Me
TsN
Me
LnPdH
3
4
. Piers, W. E.; Shapiro, P. J.; Bunel, E. E.; Bercaw, J. E.
Synlett 1990, 74.
. (a) Lehmkuhl, H.; Tsien, Y. L. Chem. Ber. 1983, 116,
TsN
IIIA
2
2
437; (b) Okamoto, S.; Livinghouse, T. J. Am. Chem. Soc.
000, 122, 1223.
1
a
3
Scheme 4. Proposed mechanism for cationic (NHC)Pd(g -allyl) cat-
alyzed cycloisomerization of dienes.
5. Christoffers, J.; Bergman, R. G. J. Am. Chem. Soc. 1996,
118, 4715.
6
7
8
. (a) Bright, A.; Malone, J. F.; Nicholson, J. K.; Powell, J.;
Shaw, B. L. J. Chem. Soc., Chem. Commun. 1971, 712; (b)
Grigg, R.; Kongkathip, B. J. Chem. Soc., Dalton. Trans.
1
978, 333; (c) Grigg, R.; Mitchell, T. R. B.; Ramasubbu,
Me
Me
Hb
A. J. Chem. Soc., Chem. Commun. 1980, 27.
TsN
Hb
Hb
TsN
. (a) Yamamoto, Y.; Ohkoshi, N.; Kameda, M.; Itoh, K. J.
Org. Chem. 1999, 64, 2178; (b) Yamamoto, Y.; Nakagai,
Y.-i.; Ohkoshi, N.; Itoh, K. J. Am. Chem. Soc. 2001, 123,
Ha
H PdLn
PdLn
b
6
372; (c) Terada, Y.; Arisawa, M.; Nishida, A. Angew.
IVA
VA
Chem., Int. Ed. 2004, 43, 4063.
. (a) Radetich, B.; RajanBabu, T. V. J. Am. Chem. Soc.
Scheme 5. b-Hydride elimination involving substrate 2.
1
998, 120, 8007; (b) RajanBabu, T. V.; Nomura, N.; Jin,
J.; Radetich, B.; Park, H.; Nandi, M. Chem. Eur. J. 1999,
, 1963; (c) B o¨ ing, C.; Franci o` , G.; Leitner, W. Adv. Synth.
5
nation to provide the desired product 1a along with the
regeneration of LnPdH. In the case of substrate 2, com-
plex IVA undergoes b-hydride elimination with H in
preference to H , which was also observed in Rh-cata-
lyzed enyne cycloisomerization (Scheme 5).
Catal. 2005, 347, 1537; (d) B o¨ ing, C.; Franci o` , G.; Leitner,
W. Chem. Commun. 2005, 1456.
b
9
. (a) Grigg, R.; Mitchell, T. R. B.; Ramasubbu, A. J. Chem.
Soc., Chem. Commun. 1979, 669; (b) Heumann, A.;
Moukhliss, M. Synlett 1998, 1211; (c) Widenhoefer, R.
A.; Perch, N. S. Org. Lett. 1999, 1, 1103; (d) Widenhoefer,
R. A. J. Am. Chem. Soc. 2000, 122, 10017; (e) Bray, K. L.;
Charmant, J. P. H.; Fairlamb, I. J. S.; Lloyd-Jones, G. C.
Chem. Eur. J. 2001, 7, 4205; (f) Kisanga, P.; Kisanga, P.;
Goj, L. A.; Widenhoefer, R. A. J. Org. Chem. 2001, 66,
a
2
2
3
In summation, a range of [(NHC)Pd(g -allyl)]Cl com-
plexes are synthesized and used as catalysts for the
cycloisomerization of dienes. To find good reaction
conditions, several different additives and solvents were
screened. Compared to other palladium catalyzed cyclo-
isomerization of 1,6-dienes, this protocol is highly
regioselective and efficient to form cyclic com-
pounds possessing an exo-methylene group. Further
mechanistic studies related to this reaction and asym-
metric cycloisomerization using chiral carbene ligands
are underway.
6
2
35; (g) Goj, L. A.; Widenhoefer, R. A. J. Am. Chem. Soc.
001, 123, 11133; (h) Bray, K. L.; Fairlamb, I. J. S.; Lloyd-
Jones, G. C. Chem. Commun. 2001, 187; (i) Fairlamb, I. J.
S.; Grant, S.; Whitwood, A. C.; Whitthall, J.; Batsanov, A.
S.; Collings, J. C. J. Organomet. Chem. 2005, 690, 4462; (j)
Park, S.; Takeuchi, D.; Osakada, K. J. Am. Chem. Soc.
2
006, 128, 3510; (k) Goj, L. A.; Cisneros, A.; Yang, W.;
Widenhoefer, R. A. J. Organomet. Chem. 2003, 687, 498.
0. Kerber, W. D.; Koh, J. H.; Gagn e´ , M. R. Org. Lett. 2004,
, 3013.
1. (a) Huang, I.; Schanz, H.-J.; Stevens, E. D.; Nolan, S. P.
Organometallics 1999, 18, 2370; (b) Bourissou, D.; Guer-
ret, O.; Gabba ¨ı , F. P.; Bertrand, G. Chem. Rev. 2000, 100,
1
1
6
Acknowledgements
This work was supported by the Korea Research Foun-
dation Grant funded by the Korean Government
MOEHRD) (KRF-2006-331-C00173 and KRF-2005-
70-C00072), the Korea Science and Engineering Foun-
39; (c) Herrmann, W. A. Angew. Chem., Int. Ed. 2002, 41,
1290; (d) Garrison, J. C.; Youngs, W. J. Chem. Rev. 2005,
105, 3978; (e) Sigman, M. S.; Jensen, D. R. Acc. Chem.
(
0
Res. 2006, 39, 221.
dation (KOSEF) for sponsoring this research through
the SRC/ERC Program of MOST/KOSEF (R11-2005-
1
2. Prior to this report, (NHC)Pd catalyzed-cycloisomeriza-
tion of bisdienes was published by Takacs. See Ref:
Takacs, J. M.; Venkataraman, S.; Andrew, R. N.; Pelter,
L. S. W. J. Organomet. Chem. 2005, 690, 6205.
0
65) and Ajou University. We thank the Korean basic
science institute for Mass spectra.

6146
Y.-J. Song et al. / Tetrahedron Letters 48 (2007) 6142–6146
1
3. Viciu, M. S.; Navarro, O.; Germaneau, R. F.; Kelly, R.
A., III; Sommer, W.; Marion, N.; Stevens, E. D.; Cavallo,
L.; Nolan, S. P. Organometallics 2004, 23, 1629.
17. Synthesis of F: The procedure of the synthesis of F was in
1
the same manner as the synthesis of D. Yield: 89%; H
NMR (CDCl ): d 7.12 (m, 2H), 7.02 (m, 4H), 6.97 (m,
3
1
4. Marion, N.; Navarro, O.; Mei, J.; Stevens, E. D.; Scott, N.
M.; Nolan, S. P. J. Am. Chem. Soc. 2006, 128, ; 4101.
5. Synthesis of D: Bis-2,6-diisopropylimidazolium salt
10H), 2.71 (d, J = 1.5 Hz, 1H), 2.11 (s, 6H), 2.03 (d,
J = 1.5 Hz, 1H), 2.00 (s, 6H), 1.42 (s, 3H). C NMR
13
1
(CDCl ): d 183.9, 141.8, 141.5, 137.7, 137.3, 131.2, 131.0,
3
(
0
0.30 g, 0.63 mmol) and potassium tert-butoxide (78 mg,
.70 mmol) in 20 mL of tetrahydrofuran were stirred at
130.8, 130.1, 127.8, 127.2, 126.4, 126.2, 122.8, 122.6, 119.8,
107.8, 49.2, 21.5, 18.5, 18.2. HRMS (M ) calcd: 745.0045,
+
room temperature for 4 h. Compound 4 in 10 mL of
tetrahydrofuran was added to the reaction mixture and the
resulting solution was stirred overnight at room temper-
ature. After the solvent was evaporated, the product was
separated by column chromatography on a silica gel
obsd: 745.0046. (C33
33 2 2 n n
H N Br PdCl) (783.34) : calcd: C,
53.67; H, 4.25; N, 3.58. Found: C, 53.48; H, 4.34; N, 3.26.
3
+
À
18. In Ref. 9e, [(g -C H )Pd(MeCN)2] [OTf] catalyzed
3 5
cycloisomerizations provide the product a at the initial
stage. However, products b and c were also observed during
the course of the reaction via Pd-catalyzed isomerization.
19. Reference for compound 2a Oppolzer, W.; Schr o¨ der, F.
Tetrahedron Lett. 1994, 35, 7939.
column eluting with hexane and ethyl acetate (v/v, 7:3).
1
Yield: 0.38 g (94%). H NMR (CDCl
3
): d 7.42 (m, 2H),
7
.11 (m, 16H), 5.01 (dd, J = 7.4 Hz, 1H), 3.03 (sep,
J = 6.6 Hz, 2H), 2.92 (sep, J = 6.6 Hz, 2H), 2.89
d, J = 6.9 Hz, 1H), 2.12 (d, J = 12.3 Hz, 1H), 1.40 (d,
J = 6.6 Hz, 12H), 1.17 (d, J = 6.6 Hz, 12H), 1.08
6
20. Compound 3a: AgSbF (8.59 mg, 0.025 mmol) and Pd
(
complex E (18.45 mg, 0.025 mmol) in dichloromethane
(3 mL) were stirred at room temperature for 1 h. N,N-
Diallylnaphthalene-2-sulfonamide (143.7 mg, 0.5 mmol)
was added to this mixture and the resulting solution was
stirred at room temperature for another 10 min. The
solvent was removed with a rotary evaporator to produce
a residue, which was purified by column chromatography
1
3
(
d, J = 6.7 Hz, 6H). C NMR (CDCl
3
): d 184.9, 145.9,
1
1
2
6
45.8, 143.4, 138.4, 136.0, 130.7, 129.7, 128.6, 128.2,
27.6, 126.7, 126.5, 124.1, 123.7, 123.6, 108.2, 108.0, 46.4,
+
8.6, 28.5, 26.4, 26.1, 22.8, 22.1. HRMS (M ) calcd:
49 2 n n
87.2930, obsd: 687.2926. (C42H N PdCl) (723.74) :
calcd: C, 69.70; H, 6.82; N, 3.87. Found: C, 69.88; H,
.66; N, 3.80.
on a silica gel eluting with hexane and ethyl acetate (v/v,
1
6
100:3). Yield: 103.8 mg (72%); H NMR (CDCl
3
): d 8.38
1
6. Synthesis of E: The procedure of the synthesis of E was in
(s, 1H), 7.96 (d, J = 8.8 Hz, 2H), 7.90 (d, J = 7.6 Hz, 1H),
7.80 (d, J = 6.8 Hz, 1H), 7.61 (t, J = 6.8 Hz, 2H), 4.84 (d,
J = 6.9 Hz, 2H), 4.02 (d, J = 13.6 Hz, 1H), 3.81 (d,
J = 14 Hz, 1H), 3.81 (dt, J = 9.2, 2.0 Hz, 1H), 2.76 (dt,
J = 8.8, 2.0 Hz, 1H), 2.69 (m, 1H), 1.019 (d, J = 6.4 Hz,
1
the same manner as the synthesis of D. Yield: 93%; H
NMR (CDCl ): d 7.32 (m, 6H), 7.11 (m, 10H), 6.87 (t,
3
J = 7.4 Hz, 2H), 3.17 (sep, J = 6.4 Hz, 2H), 2.74 (sep,
J = 6.4 Hz, 2H), 2.66 (s, 1H), 2.18 (s, 1H), 1.43 (d,
J = 6.6 Hz, 12H), 1.24 (d, J = 7.2 Hz, 12H), 1.20 (s, 3H),
1
3
3H). C NMR (CDCl ): d 149.2, 135.03, 133.2, 132.3,
3
1
3
0
1
1
2
.95 (m, 12H). C NMR (CDCl ): d 186.2, 146.1, 146.0,
129.3, 128.1, 127.7, 123.2, 106.4, 55.5, 52.6, 37.9, 16.4.
3
+
42.4, 142.2, 136.3, 130.9, 130.6, 129.6, 128.1, 127.1, 126.1,
25.8, 124.1, 123.8, 123.7, 120.7, 105.8, 49.3, 28.7, 28.4,
7.0, 25.7, 23.1, 21.6, 21.2. HRMS (M ) calcd: 701.3086,
HRMS [M+H] calcd: 288.10, obsd: 288.11. FTIR(NaCl):
À1
2960, 2920, 2870, 1340, 1160 cm
.
+
21. Mecking, S.; Keim, W. Organometallics 1996, 15, 2650.
22. Cao, P.; Wang, B.; Zhang, X. J. Am. Chem. Soc. 2000,
122, 6490.
obsd: 701.3088. (C43
51 2 n n
H N PdCl) (737.76) : calcd: C,
70.01; H, 6.97; N, 3.80. Found: C, 70.46; H, 6.93; N, 3.56.