Platinum-catalyzed allylation of aminonaphthalenes with allylic acetates in water

Article abstract of DOI:10.1016/j.tet.2008.07.037

The activation of C-O bonds in allylic acetates in water as a suspension medium has been accelerated by carrying out the reactions in the presence of platinum complexes associated with ligands. The platinum-catalyzed allylation of aminonaphthalenes using allylic acetates gave the corresponding N-allylic aminonaphthalenes in good yields.

Full text of DOI:10.1016/j.tet.2008.07.037

Tetrahedron 64 (2008) 9625–9629
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Platinum-catalyzed allylation of aminonaphthalenes with allylic acetates in water
,b,
Kim-Hong Gan a, Ciou-Jyu Jhong a, Yi-Jen Shue a, Shyh-Chyun Yang a
*
a Faculty of Pharmacy, College of Pharmacy, Kaohsiung Medical University, Kaohsiung 807, Taiwan, ROC
b Center of Excellence for Environmental Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan, ROC
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 7 April 2008
Received in revised form 9 July 2008
Accepted 11 July 2008
Available online 16 July 2008
The activation of C–O bonds in allylic acetates in water as a suspension medium has been accelerated by
carrying out the reactions in the presence of platinum complexes associated with ligands. The platinum-
catalyzed allylation of aminonaphthalenes using allylic acetates gave the corresponding N-allylic ami-
nonaphthalenes in good yields.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords:
Platinum-catalyzed
Allylation
Water
Aminonaphthalenes
Allylic acetates
1. Introduction
Ti(OiPr)4 in benzene.36–39 Organic reactions in water have recently
attracted much attention, because water is a safe and economical
A principal goal of organometallic chemistry is the catalytic
synthesis of organic compounds by using the chemistry of organic
ligands covalently bound to transition metals. Transition metals, in
particular palladium and rhodium, have been workhorse elements
in many commercialized catalytic processes that include hydroge-
nations, hydroformylations, acetic acid production, and other C–C
substitute for conventional organic solvent.40–46 Thus, de-
velopment of atom-economical reactions in water is one of the
most important goals of synthetic chemistry. However, platinum-
catalyzed allylation has attracted little attraction.47–50 Herein, we
will describe a novel catalysis of platinum complex, which mediates
N-allylation of aminonaphthalenes with allylic acetates using water
as solvent.
and C–H bond forming processes.1–4 Transition metal
h
3-allyl
complexes, as well as transition metal -alkyl complexes, play
s
important roles as active species and key intermediates in many
reactions catalyzed by transition metal complexes.5 The palladium-
catalyzed allylation is a powerful tool for C–C, C–N, and C–O bond
formation, which has been widely applied to organic chemistry.6–8
The processes have been shown to proceed by attack of nucleo-
2. Results and discussion
The platinum-catalyzed allylation of 1-aminonaphthalene with
allyl acetate was investigated under various conditions (Scheme 1).
When a mixture of 1-aminonaphthalene (1a, 2 mmol) and allyl
acetate (2a, 2.4 mmol) was stirred in the presence of catalytic
amounts of Pt(acac)2 (0.02 mmol) and PPh3 (0.08 mmol) in water at
room temperature for 30 min, N-allyl-1-naphthylamine (3a) was
formed in only 17% yield (entry 1 in Table 1). The reaction, under
reflux, increased the yields of products 3a and N,N-diallyl-1-
naphthylamine (4a) to 90 and 6%, respectively (entry 3). The re-
action gave 59% yield under reflux for 15 min (entry 4). As expected,
increasing the relative amount of allyl acetate favored the forma-
tion of the desired diallylated product 4a (entries 5 and 6). The
reaction did not occur in the absence of the platinum species (entry
7) or phosphine ligand (entry 8). Using MeOH and EtOH as solvents
gave only low yields of products (entries 9 and 10). Among the
platinum catalysts including Pt(acac)2 (entry 3), cis-PtCl2(PhCN)2
(entry 11), cis-PtCl2(PPh3)2 (entry 12), PtCl2 (entry 13), PtI2 (entry
philes on intermediate
h
3-allylpalladium(II) complexes generated
by oxidative addition of allylic compounds including halides,9–11
esters,12–20 carbonates,21–25 carbamates,26,27 phosphates,28,29 and
related derivatives30–33 to a Pd(0) complex. Aromatic amines have
not been used commonly in allylic amination, presumably because
they are less nucleophilic than the more commonly used benzyl-
amine or stabilized anionic nitrogen nucleophiles.34,35 We have
reported our attempts and some successful applications of a pro-
cess involving the C–O bond cleavage with direct use of allylic al-
cohols catalyzed by palladium complexes in the presence of
* Corresponding author. Fax: þ886 7 3210683.
E-mail address: scyang@kmu.edu.tw (S.-C. Yang).
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.07.037

9626
K.-H. Gan et al. / Tetrahedron 64 (2008) 9625–9629
(2-furyl)3P, and (2-pyridyl)Ph2P (entries 3 and 21–30) showed that
AcO
PPh3 (entry 3), (3-MeC6H4)3P (entry 23), (4-MeC6H4)3P (entry 24),
(4-FC6H4)3P (entry 25), (4-ClC6H4)3P (entry 26), and (2-furyl)3P
(entry 29) were the most effective ligands. Using O[Si(CH3)2C]
CH2]2Pt associated with (4-FC6H4)3P as catalyst gave 99% yield
(entry 31). The bidentate ligands such as dppm, dppb, and dpph
gave worst results (entries 32–34).
2a
+
Pt catalyst, ligand
H2O
N
NH
NH2
1a
3a
4a
Results for N-allylation of a number of aminonaphthalenes
(1b–l) with allyl acetate (2a) using Pt(acac)2 and PPh3 in water are
summarized in Table 2. 2-Methy-1-aminonaphthalene (1b) gave
mono- and diallylated products in high yields (entry 1). 4-Bromo-1-
aminonaphthalene (1c) also reacted to give the N-allylated prod-
ucts in moderate yields (entry 2). Using aminonaphthalenes having
strong electron-withdrawing groups, such as the cyano group,
under reflux for 3 h, only the monoallylated product N-allyl-1-(4-
cyanonaphthyl)amine (3d) was obtained, however, in a very low
yield (entry 3). These differences in reactivity could be related to
the nucleophilicity of the corresponding aminonaphthalene. The
lower yield observed may arise from the nature of the cyano group.
The more acidic 1-amino-4-cyanonaphthalene (1d) is probably less
Scheme 1. Allylation of 1-aminonaphthalene (1a) with allyl acetate (2a).
14), Pt(CN)2 (entry 15), O[Si(CH3)2C]CH2]2Pt (entry 16),
Pt(CH2]CH2)(PPh3)2 (entries 17 and 18), and Pt(PPh3)4 (entries 19
and 20) were used. Pt(acac)2, O[Si(CH3)2C]CH2]2Pt, and
Pt(CH2]CH2)(PPh3)2 were found to be the superior. The use of
O[Si(CH3)2C]CH2]2Pt as catalyst was cheaper than palladium re-
agents and could give good results. However, using
Pt(CH2]CH2)(PPh3)2 or Pt(PPh3)4 with extra PPh3 as catalyst
increased the yield of products (entries 18 and 20). The catalytic
reactivity of the phosphine ligands is likely due to improved cata-
lyst stability. In the presence of various monodentate ligands
including PPh3, Bu3P, (2-MeC6H4)3P, (3-MeC6H4)3P, (4-MeC6H4)3P,
(4-FC6H4)3P, (4-ClC6H4)3P, (4-MeOC6H4)3P, [2,4,6-(MeO)3C6H2]3P,
reactive in attack on the
naphthalene (1e) and 5-amino-1-naphthalenesulfonic acid (1f)
under reflux for 3 h gave no products (entries and 5).
p-allyl complex. Thus, 4-nitro-1-amino-
4
Table 1
Platinum-catalyzed allylation of 1-aminonaphthalene (1a) with allyl acetate (2a)a
Entry
Platinum catalyst
Ligand
Yield (%)b (3aþ4a)
Yield (%)b of 3a
Yield (%)b of 4a
1c
Pt(acac)2
Pt(acac)2
Pt(acac)2
Pt(acac)2
Pt(acac)2
Pt(acac)2
d
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
d
17
28
96
59
83
99
0
17
27
90
53
79
54
2d
3
1
6
6
4
45
4e
5f
6g
7
8
Pt(acac)2
0
9h
10i
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
Pt(acac)2
Pt(acac)2
cis-PtCl2(PhCN)2
cis-PtCl2(PPh3)2
PtCl2
PtI2
Pt(CN)2
O[Si(CH3)2C]CH2]2Pt
Pt(CH2]CH2)(PPh3)2
Pt(CH2]CH2)(PPh3)2
Pt(PPh3)4
Pt(PPh3)4
Pt(acac)2
Pt(acac)2
Pt(acac)2
Pt(acac)2
Pt(acac)2
Pt(acac)2
Pt(acac)2
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
d
2
5
2
5
79
81
85
16
2
89
77
95
37
87
3
11
95
96
99
99
61
1
98
68
99
3
73
75
79
16
2
76
74
90
37
80
3
6
6
6
13
3
5
PPh3
d
PPh3
Bu3P
7
(2-MeC6H4)3P
(3-MeC6H4)3P
(4-MeC6H4)3P
(4-FC6H4)3P
(4-ClC6H4)3P
(4-MeOC6H4)3P
[2,4,6-(MeO)3C6H2]3P
(2-Furyl)3P
(2-Pyridyl)Ph2P
(4-FC6H4)3P
Dppmj
3
8
13
6
28
25
5
82
90
71
74
56
1
77
63
76
3
Pt(acac)2
Pt(acac)2
Pt(acac)2
O[Si(CH3)2C]CH2]2Pt
Pt(acac)2
21
5
23
Pt(acac)2
Pt(acac)2
Dppbk
8
11
8
11
Dpphl
a
Reaction conditions: 1a (2 mmol), 2a (2.4 mmol), Pt catalyst (0.02 mmol), and PPh3 (0.08 mmol) in water (5 mL) were refluxed for 30 min.
b
c
d
e
f
Isolated yield.
Stirred at room temperature.
Stirred at 50 ꢀC.
Reflux for 15 min.
1.6 mmol of 2a was used.
4 mmol of 2a was used.
Using MeOH as solvent.
Using EtOH as solvent.
1,3-Bis(diphenylphosphino)methane.
1,4-Bis(diphenylphosphino)butane.
1,6-Bis(diphenylphosphino)hexane.
g
h
i
j
k
l

K.-H. Gan et al. / Tetrahedron 64 (2008) 9625–9629
9627
Table 2
Table 2 (continued)
Reaction of aromatic amines (1b–l) with allyl acetate (2a)a
Entry
10c
1
Yieldsb (%)
Entry
1
Yieldsb (%)
H
N
N
CH3
CH3
CH3
NH
N
1
1k
NH2
3k (52)
3k (85)
1b
11d
1k
3b (58)
4b (34)
Br
Br
Br
H
N
N
12d
2c
N
NH
S
1l
S
NH2
CN
3l (70)
1c
3c (52)
4c (2)
a
Reaction conditions: 1 (2 mmol), 2a (2.4 mmol), Pt(acac)2 (0.02 mmol), and PPh3
(0.08 mmol) in water (5 mL) were refluxed for 30 min.
CN
b
Isolated yield.
Reflux for 1 h.
Reflux for 3 h.
c
d
3d
NH
NH2
NO2
2-Aminonaphthalene (1g) gave mono- and diallylated products 3g
and 4g in the yields of 67 and 25%, respectively (entry 6). 3-Ami-
noquinoline (1h) and N-ethyl-1-aminonaphthalene (1i) reacted to
give the N-allylated products in moderate yields (entries 7 and 8).
The sterically more demanding secondary aminonaphthalene (1j)
gave lower yields (entry 9). Secondary aromatic amines, such as
diphenylamine (1k) and phenothiazine (1l), also reacted to give the
N-allylamine in moderate yield (entries 10 and 12). Increasing the
refluxing time to 3 h, diphenylamine (1i) could give good yields of
products (entry 11).
The results for amination of a number of derivatives of allylic
alcohols 2b–f with 1-aminonaphthalene (1a) using Pt(acac)2 and
PPh3 are summarized in Table 3. Amination of trans-2-hexen-1-yl
acetate (2b) gave mixtures of monoallylated, diallylated, and
regioisomeric aminonaphthalenes 5, 6, and 7 in yields of 54, 18, and
24%, respectively (entry 1 in Table 3). These products may all be
1d
3d (11)
4d
d
d
NH2
1e
SO3H
5d
d
d
NH2
1f
derived from the same
at either the C-1 or C-3 position. The reaction is considered to
proceed via -allylplatinum intermediates. The loss of the stereo-
chemistry of the starting acetate 2b is due to a rapid
h3
interconversion of the -allyl intermediate compared to the rate of
amination of this intermediate. In the reaction of aromatic allylic
acetate 2c, the corresponding monoallylated and diallylated prod-
ucts were formed in overall 99% yields (entry 2). Amination of
geranyl acetate (2d) gave only monoallylated product 10 in 20%
yield (entry 3). Increasing the refluxing time to 3 h could give the
product 10 in 56% yield (entry 4). With the allyl chloride (2e), the
reaction produces only 3a in 23% yield (entry 5). Allyl carbonate (2f)
gave products in high yields (entry 6).
p-allyl intermediate, which can be attacked
N
NH
6
NH2
NH2
p
1g
s
$
$s
3g (67)
4g (25)
p
N
N
N
7c
NH
N
1h
3h (42)
4h (12)
N
8
NH
3. Conclusion
1i
3i (75)
In summary, we have developed a catalytic system that en-
ables reactions of aromatic amines with allylic acetates as ally-
lating agents in water. This is a simple and efficient route for C–N
bond formation. The reaction did not occur in the absence of the
phosphine ligand or platinum catalyst. The amination of allylic
acetates worked well with aminonaphthalenes, giving generally
good yields of the corresponding allylic aminonaphthalenes.
Aminonaphthalenes with steric constraints gave lower chemical
yields.
9d
NH
N
3j (20)
1j

9628
K.-H. Gan et al. / Tetrahedron 64 (2008) 9625–9629
Table 3
Reaction of 1-aminonaphthalene (1a) with allylic compounds (2b–f)a
Entry
2
Yieldsb (%)
NH
N
OAc
1
HN
2b
7 (24)
5 (54)
6 (18)
AcO
Ph
2
HN
8 (66)
Ph
Ph
N
Ph
2c
9 (33)
NH
OAc
3
2d
10 (20)
4c
5
2d
10 (56)
Cl
3a (23)
3a (68)
2e
OCOOCH3
2f
6
4a (31)
a
Reaction conditions: 1a (2 mmol), 2 (2.4 mmol), Pt(acac)2 (0.02 mmol) and PPh3 (0.08 mmol) in water (5 mL) were refluxed for 30 min.
Isolated yield.
Reflux for 3 h.
b
c
4. Experimental
4.2.1. N-(3,7-Dimethyl-2E,6-octadienyl)-1-naphthylamine (10)
Light yellow thick oil. IR (KBr):
3422 cmꢁ1 1H NMR
(400 MHz, CDCl3): 1.62 (s, 3H, CH3), 1.70 (s, 3H, CH3), 1.74 (s, 3H,
n
.
4.1. General considerations
d
CH3), 2.06–2.17 (m, 4H, CH2ꢂ2), 3.88 (d, J¼6.8 Hz, 2H, CH2), 4.21
(br s, 1H, NH), 5.09–5.14 (m, 1H, vinyl H), 5.46–5.50 (m, 1H, vinyl
H), 6.65 (d, J¼7.2 Hz, 1H, ArH), 7.25 (d, J¼8.0 Hz, 1H, ArH), 7.36 (t,
J¼8.0 Hz, 1H, ArH), 7.40–7.45 (m, 2H, ArH), 7.77–7.83 (m, 2H,
IR absorption spectra were recorded on a Perkin–Elmer System
2000 FT-IR spectrophotometer. Proton and carbon-13 NMR were
measured with a Unity-400 or Mercury Plus-400 spectrometer.
Carbon multiplicities were obtained from DEPT experiments.
ArH). 13C NMR (100 MHz, CDCl3):
d 16.4 (CH3), 17.7 (CH3), 25.7
Chemical shifts (
d
) and coupling constants (Hz) were measured
(CH3), 26.4 (CH2), 39.5 (CH2), 42.2 (CH2), 104.5 (CH), 117.2 (CH),
119.9 (CH), 121.3 (CH), 123.4 (C), 123.9 (CH), 124.6 (CH), 125.6
(CH), 126.6 (CH), 128.6 (CH), 131.7 (C), 134.2 (C), 139.5 (C), 143.5
(C). EIMS: m/z 279 (Mþ), 264, 236, 222, 210, 197, 180, 168, 154,
143, 127, 115, 89, 77. EI-HRMS calcd for C20H25N: 279.1987, found:
279.1987.
with respect to TMS or chloroform-d1. MS and high-resolution mass
spectra (HRMS) were taken on a Thermo-Finnigan trace GC or
Finnigan MAT-95XL instrument, with a direct inlet system.
4.2. Generalprocedure for the platinum-catalyzed allylation of
aminonaphthalenes. Reaction with 1-aminonaphthalene (1a)
Acknowledgements
A mixture of 1-aminonaphthalene (1a) (286 mg, 2 mmol), allyl
acetate (2a) (240 mg, 2.4 mmol), Pt(acac)2 (7.8 mg, 0.02 mmol),
and PPh3 (21 mg, 0.08 mmol) in water (5 mL) was refluxed for
30 min. After the mixture was cooled to room temperature, water
and brine were added. The organic materials were extracted with
dichloromethane, dried over magnesium sulfate, and concen-
trated under vacuum. Column chromatography (ethyl acetate/
n-hexane 1:4) of the residue afforded 3a and 4a in 90 and 6%
yields, respectively.
This work was partly supported by the National Science Council
in Taiwan under grants 95-2113-M-037-011-MY3 and the funds
KMU-EM-97-2.1a and KMU-EM-97-2.1b.
References and notes
1. Walsh, P. J.; Baranger, A. M.; Bergman, R. G. J. Am. Chem. Soc. 1992, 114, 1708.
2. McGrane, P. L.; Jensen, M.; Livinghouse, T. J. Am. Chem. Soc. 1992, 114, 5459.
3. Baranger, A. M.; Walsh, P. J.; Bergman, R. G. J. Am. Chem. Soc. 1993, 115, 2753.
4. Brunet, J.; Commenges, G.; Neibecker, D.; Philippot, K. J. Organomet. Chem. 1994,
469, 221.
Products 3a,50 4a,50 3b,50 4b,50 3c,50 4c,50 3d,50 3g,50 4g,50 3h,50
4h,50 3i,50 3j,50 3k,39 3l,39 5,50 6,50 7,50 8,50 and 950 are known.

K.-H. Gan et al. / Tetrahedron 64 (2008) 9625–9629
9629
5. Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principles and Applications
of Organotransition Metal Chemistry; University Science Books: Mill Valley, CA,
1987.
6. Sakamoto, M.; Shimizu, I.; Yamamoto, A. Bull. Chem. Soc. Jpn. 1996, 69, 1065.
7. Tsuji, J. Transition Metal Reagents and Catalysts; Wiley: New York, NY, 2000.
8. Tsutsumi, K.; Yabukami, T.; Fujimoto, K.; Kawase, T.; Morimoto, T.; Kakiuchi, K.
Organometallics 2003, 22, 2996.
27. Hayashi, T.; Yamamoto, A.; Ito, Y. Tetrahedron Lett. 1987, 28, 4837.
28. Ziegler, F. E.; Wester, R. T. Tetrahedron Lett. 1986, 27, 1225.
29. Ziegler, F. E.; Cain, W. T.; Kneisley, A.; Stirchak, E. P.; Wester, R. T. J. Am. Chem.
Soc. 1988, 110, 5442.
30. Imidoesters: Schenck, T. G.; Bosnich, B. J. Am. Chem. Soc. 1985, 107, 2058.
31. Xanthates: Auburn, P. R.; Wheland, J.; Bosnich, B. J. Chem. Soc., Chem. Commun.
1986, 146.
9. Goldeski, S. A. In Nucleophiles with Allyl-Metal Complexes; Trost, B. M., Fleming,
I., Eds.; Comprehensive Organic Synthesis; Pergamon: New York, NY, 1991; Vol.
4, Chapter 3.3.
32. Nitrogroups: Tamura, R.; Kamimura, A.; Ono, N. Synthesis 1991, 423.
33. Sulfones: Trost, B. M.; Schmuff, N. R.; Miller, M. J. J. Am. Chem. Soc. 1980, 102,
5979.
10. Harrington, P. J. In Transition Metal Allyl Complexes: Pd, W, Mo-assisted Nu-
cleophilic Attack; Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.; Compre-
hensive Organometallic Chemistry II; Pergamon: New York, NY, 1995; Vol. 12,
Chapter 8.2.
34. Takeuchi, R.; Ue, N.; Tanabe, K.; Yamashita, K.; Shiga, N. J. Am. Chem. Soc. 2001,
123, 9525.
35. Ozawa, F.; Okamoto, H.; Kawagishi, S.; Yamamoto, S.; Minami, T.; Yoshifuji, M.
J. Am. Chem. Soc. 2002, 124, 10968.
11. Tsuji, J. Palladium Reagents and Catalysts; Wiley: New York, NY, 1995.
12. Trost, B. M. Angew. Chem., Int. Ed. Engl. 1989, 28, 1173.
13. Oppolzer, W. Angew. Chem., Int. Ed. Engl. 1989, 28, 38.
14. Tsuji, J. Synthesis 1990, 739.
15. Trost, B. M. Pure Appl. Chem. 1992, 64, 315.
16. Backvall, J. E. Pure Appl. Chem. 1992, 64, 429.
36. Yang, S.-C.; Tsai, Y.-C. Organometallics 2001, 20, 763.
37. Shue, Y.-J.; Yang, S.-C.; Lai, H.-C. Tetrahedron Lett. 2003, 44, 1481.
38. Yang, S.-C.; Lai, H.-C.; Tsai, Y.-C. Tetrahedron Lett. 2004, 45, 2693.
39. Hsu, Y.-C.; Gan, K.-H.; Yang, S.-C. Chem. Pharm. Bull. 2005, 53, 1266.
40. Organic Synthesis in Water; Grieco, P. A., Ed.; Blackie Academic and Professional:
London, 1998.
17. Giambastiani, G.; Poli, G. J. Org. Chem. 1998, 63, 9608.
18. Uozumi, Y.; Danjo, H.; Hayashi, T. J. Org. Chem. 1999, 64, 3384.
19. Rajesh, S.; Banerji, B.; Iqbal, J. J. Org. Chem. 2002, 67, 7852.
20. Wallner, O. A.; Szabo, K. J. J. Org. Chem. 2003, 68, 2934.
21. Stary, I.; Zajicek, J.; Kocovsky, P. Tetrahedron 1992, 48, 7229.
22. Goux, C.; Massacret, M.; Lhoste, P.; Sinou, D. Organometallics 1995, 14, 4585.
23. Deardorff, D. R.; Savin, K. A.; Justman, C. J.; Karanjawala, Z. E.; Sheppeck, J. E., II;
Hager, D. C.; Aydin, N. J. Org. Chem. 1996, 61, 3616.
41. Li, C.-J.; Chan, T.-H. Organic Reactions in Aqueous Media; John Wiley & Sons: New
York, NY, 1997.
42. Lindstro¨m, U. M. Chem. Rev. 2002, 102, 2751.
43. Manabe, K.; Kobayashi, S. Chem.dEur. J. 2002, 8, 4095.
44. Huang, J.; Zhou, L.; Jiang, H. Angew. Chem., Int. Ed. 2006, 45, 1945.
45. Yang, S.-C.; Hsu, Y.-C.; Gan, K.-H. Tetrahedron 2006, 62, 3949.
46. Gan, K.-H.; Jhong, C.-J.; Yang, S.-C. Tetrahedron 2008, 64, 1204.
47. Tsuji, Y.; Shida, J.; Takeuchi, R.; Watanabe, Y. Chem. Lett. 1984, 889.
48. Tsuji, Y.; Takeuchi, R.; Ogawa, H.; Watanabe, Y. Chem. Lett. 1986, 293.
49. Yang, S.-C.; Tsai, Y.-C.; Shue, Y.-J. Organometallics 2001, 20, 5326.
50. Yang, S.-C.; Feng, W.-H.; Gan, K.-H. Tetrahedron 2006, 62, 3752.
24. Kadota, J.; Katsuragi, H.; Fukumoto, Y.; Murai, S. Organometallics 2000, 19, 979.
25. Kamijo, S.; Jin, T.; Yamamoto, Y. J. Am. Chem. Soc. 2001, 123, 9453.
26. Minami, I.; Yuhara, M.; Tsuji, J. Tetrahedron Lett. 1987, 28, 2737.