Palladium-catalyzed carbonylative cyclization of β-bromo-α, β-unsaturated carboxylic acids with 2,2-dimethylhydrazine leading to 1-(dimethylamino)-1H-pyrrole-2,5-diones

Article abstract of DOI:10.1002/aoc.3111

β-Bromo-α,β-unsaturated carboxylic acids are carbonylatively cyclized with 2,2-dimethylhydrazine under carbon monoxide pressure in THF in the presence of a catalytic amount of a palladium catalyst along with a base to give 1-(dimethylamino)-1H-pyrrole-2,5-diones. Copyright

Full text of DOI:10.1002/aoc.3111

Full Paper
Received: 2 September 2013
Revised: 4 November 2013
Accepted: 10 November 2013
Published online in Wiley Online Library: 21 January 2014
(wileyonlinelibrary.com) DOI 10.1002/aoc.3111
Palladium-catalyzed carbonylative cyclization
of β-bromo-α,β-unsaturated carboxylic acids
with 2,2-dimethylhydrazine leading to
1-(dimethylamino)-1H-pyrrole-2,5-diones
Yeon Kyu Bae and Chan Sik Cho*
β-Bromo-α,β-unsaturated carboxylic acids are carbonylatively cyclized with 2,2-dimethylhydrazine under carbon monoxide
pressure in THF in the presence of a catalytic amount of a palladium catalyst along with a base to give 1-(dimethylamino)-
1H-pyrrole-2,5-diones. Copyright © 2014 John Wiley & Sons, Ltd.
Keywords: β-bromo-α,β-unsaturated carboxylic acids; carbonylative cyclization; 2,2-dimethylhydrazine; 1-(dimethylamino)-1H-pyrrole-
2,5-diones; palladium catalyst
Introduction
Results and Discussion
Transition metal-catalyzed carbonylation followed by cyclization
(carbonylative cyclization) has been widely explored and used
as a promising synthetic tool for the construction of the scaffolds
of many pharmacologically and biologically active lactones
and lactams.[1–6] During the course of our ongoing studies
directed towards palladium-catalyzed carbonylative cyclizations,
we recently reported on the synthesis of several carbonyl-
group-containing heterocycles such as furanones,[7–9] alkyl 2,5-
dihydro-5-oxofuran-2-carboxylates,[10] hydroisoindol-1-ones,[11]
1-aryl-1H-pyrrol-2(5H)-ones[12] and maleic anhydrides[13] from
β-bromo-α,β-unsaturated aldehydes and their derivatives using
such a carbonylative cyclization. The β-bromo-α,β-unsaturated
aldehydes and their derivatives can be readily prepared from
the corresponding α-methylene-containing ketones by the
bromination conditions of the Vilsmeier–Haak reaction[14,15] and
subsequent transformation and used as a building block for the
construction of various cyclic compounds.[16–27] Under these
circumstances, among the synthesis of carbonyl-group-containing
heterocycles via such a carbonylative cyclization, β-bromo-α,
β-unsaturated carboxylic acids were found to be cyclized with
primary amines in the presence of a palladium catalyst under
carbon monoxide pressure to afford N-alkylmaleimides.[28] The
present work was realized during the course of the extension
of this protocol to the reaction with 2,2-dimethylhydrazine.
Herein, we describe palladium-catalyzed carbonylative cyclization
of β-bromo-α,β-unsaturated carboxylic acids with 2,2-dimethylhy-
drazine leading to 1-(dimethylamino)-1H-pyrrole-2,5-diones.
It is known that 2-(dimethylamino)isoindolinone-1,3-dione
(N-dimethylamino phthalimide), an analogue of 1-(dimethylamino)-
1H-pyrrole-2,5-diones 3, is used for the precursor for the synthesis
of 3-substituted phthalimidines, 4-substituted chlorophthalazines,
dihydrobenzoazepinediones, 2-pyrazolylbenzoic acids and 2-
pyrazolylbenzohydrazides.[29,30]
The results of several attempted carbonylative cyclizations of
2-bromocyclohex-1-enecarboxylic acid (1a) with 2,2-dimethylhy-
drazine (2) for the optimization of reaction conditions are listed
in Table 1. Treatment of 1a with an equimolar amount of 2 under
CO (10 atm) in THF at 120 °C for 15 h in the presence of a catalytic
amount of PdCl2 and dppp (1,3-bis(diphenylphosphino)propane)
along with Et3N afforded 2-(dimethylamino)-4,5,6,7-tetrahydro-
2H-isoindole-1,3-dione (3a) in 30% isolated yield (entry 1). The
molar ratio of [2]/[1a] affected the yield of 3a and the yield
increased with the increase of the molar ratio up to 3 (entries
1–3). Lower carbon monoxide pressure resulted in a decreased
yield of 3a (entry 4). Performing the reaction in the absence of
base under the molar ratio of [2]/[1a] = 5 resulted in a similar
yield of 3a (entry 5). Among solvents examined under the
employed conditions, THF and dioxane were shown to be the
solvent of choice (entries 3, 6–8). With other bases such as
Na2CO3 and NaOAc combined with PdCl2/dppp in MeCN, the
yield of 3a was generally lower than that when Et3N was
employed (entries 8–10). From the activity of several palladium
precursors examined under the employed conditions, PdCl2
combined with dppf [1,1′-bis(diphenylphosphino)ferrocene]
exhibited similar catalytic activity to PdCl2 combined with
dppp (entries 3, 11–14). As a result, the best result in terms
of product 3a yield and complete conversion of 1a was
accomplished by the standard set of reaction conditions shown
in entry 3 of Table 1.
*
Correspondence to: Chan Sik Cho, Department of Applied Chemistry, Kyungpook
National University, Daegu 702-701, South Korea. Email: cscho@knu.ac.kr
Department of Applied Chemistry, Kyungpook National University, Daegu
702-701, South Korea
Appl. Organometal. Chem. 2014, 28, 225–229
Copyright © 2014 John Wiley & Sons, Ltd.

Y. K. Bae and C. S. Cho
Table 1. Optimization of conditions for the reaction of 1a with 2a
Table 2. Palladium-catalyzed synthesis of 1-(dimethylamino)-1H-
pyrrole-2,5-dionesa
Me
Me
N
cat. [Pd]
PdCl2/dppp,
Et3N
CO
N
Me
Me
COOH
+
Br
NH2
N
O
O
O
N
N
(10 atm)
THF, CO
(10 atm)
NH2
N
Me
OH
Me
Me
O
O
Me
Br
2
1a
3a
2
1
3
Entry [2]/
[1a]
Pd
catalyst
Base
Solvent
Time Yield
(h)
(%)
1
3
Isolated yield (%)
1
1
2
3
3
5
3
3
3
3
3
3
3
3
3
PdCl2/dppp
PdCl2/dppp
PdCl2/dppp
PdCl2/dppp
PdCl2/dppp
PdCl2/dppp
PdCl2/dppp
PdCl2/dppp
PdCl2/dppp
PdCl2/dppp
PdCl2(PPh3)2
Pd(OAc)2/PPh3
PdCl2(PhCN)2
PdCl2/dppf
Et3N
THF
15
3
30
55
62
50
54
17
57
38
22
32
18
2
O
O
2
Et3N
Et3N
Et3N
-
THF
Me
N
Me
3
4b
THF
3
N
OH
THF
3
Br
O
5
THF
15
3
1a
Me
1b
3a
62
6
Et3N
Et3N
Et3N
Na2CO3
NaOAc
Et3N
Et3N
Et3N
Et3N
DMF
Dioxane
MeCN
MeCN
MeCN
THF
7
3
O
O
8
15
15
15
3
Me
Me
N N
9
OH
10
11
12
13
14
Me
Br
O
THF
3
3b
56
THF
3
2
THF
3
62
O
O
aReaction conditions: 1a (0.5mmol), palladium catalyst (0.025 mmol),
ligand (bidentate ligand: 0.03mmol; PPh3: 0.05mmol), base
(2mmol), solvent (7ml), CO (10 atm), 120 °C.
bUnder CO (5 atm).
Ph
Me
Ph
OH
N N
Me
Br
O
1c
3c
40
48
O
O
Me
N
Me
After the reaction conditions had been optimized, various
β-bromo-α,β-unsaturated carboxylic acids 1 were subjected to
the reaction with 2 in order to investigate the reaction scope,
and several representative results are summarized in
Table 2.[14,15,31] From the carbonylative cyclization of six-
membered β-bromo-α,β-unsaturated carboxylic acids 1b and 1c
with 2, the corresponding 1-(dimethylamino)-1H-pyrrole-2,5-
diones 3b and 3c were also produced in similar yields
irrespective of methyl and phenyl substituents on 1b and 1c.
With β-bromo-α,β-unsaturated carboxylic acids (1d–f) having
various ring sizes, the carbonylative cyclized products (3d–f)
were produced in the range of 48–84% yields, and higher yield
was observed with eight- and 12-membered β-bromo-α,β-
unsaturated carboxylic acids 1e and 1f. However, not shown
in Table 2, similar treatment of five-membered β-bromo-α,β-
N
OH
Br
O
1d
1e
3d
O
Me
N
Me
N
O
3e
80
84
O
Me
N
Me
N
O
unsaturated carboxylic acid with
2 did not afford the
1f
3f
corresponding product at all. To test for the effect of the
position of bromide and carboxy group on β-bromo-α,β-
unsaturated carboxylic acids 1g and 1h were employed. The
carbonylative cyclization similarly took place with both 1g and
1h irrespective of their positions. However, lower reaction rate
and yield were observed with acyclic β-bromo-α,β-unsaturated
carboxylic acids (1i and 1j).
O
O
Me
N
Me
N
OH
Br
O
On the other hand, not shown in Table 2, similar treatment
of 1a with hydrazine hydrate (50–60%) did not afford an
identifiable product at all. However, the reaction of 1a with
phenylhydrazine under the employed conditions afforded
4,5,6,7-tetrahydro-2-(phenylamino)-2H-isoindole-1,3-dione (3j)
in 45% yield.
1g
3g
54
(Continues)
wileyonlinelibrary.com/journal/aoc
Copyright © 2014 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2014, 28, 225–229

Palladium-catalyzed carbonylative cyclization
The starting β-bromo-α,β-unsaturated carboxylic acids were
prepared via two steps from the corresponding ketones
according to literature procedures.[14,15,31] Commercially
available organic and inorganic compounds were used without
further purification.
Table 2. (Continued)
PdCl2/dppp,
Et3N
Me
Me
O
N
N
THF, CO
(10 atm)
NH2
N
OH
Me
O
O
Me
Br
General Procedure for Palladium-Catalyzed Carbonylative
Cyclization of β-Bromo-α,β-Unsaturated Carboxylic Acids
with N,N-Dimethylhydrazine Leading to 1-(Dimethylamino)-
1H-Pyrrole-2,5-Diones
2
1
3
1
3
Isolated yield
To a 50 ml stainless steel autoclave were added β-bromo-α,β-
unsaturated carboxylic acid 1 (0.5 mmol), N,N-dimethylhydra-
zine (2) (0.090 g, 1.5 mmol), PdCl2 (0.004 g, 0.025 mmol), dppp
(0.012 g, 0.03 mmol), Et3N (0.202 g, 2 mmol) and THF (7 ml).
After the system was flushed and then pressurized with CO to
10 atm, the reaction mixture was allowed to react at 120 °C
for 3 h. The reaction mixture was filtered through a short silica
gel column (ethyl acetate) to eliminate inorganic salts. Removal
of the solvent left a crude mixture, which was separated by
thin-layer chromatography (silica gel, ethyl acetate–hexane
mixture) to give 1-(dimethylamino)-1H-pyrrole-2,5-diones 3.
Except for known 3a[30] and 3i,[32] all new products prepared
by the above procedure were characterized spectroscopically
as shown below.
(%)
Br
O
OH
1h
3g
41
O
O
Me
N
Me
OH
N
Ph
Ph
Br
O
1i
3h
10
33
O
O
2-(Dimethylamino)-4,5,6,7-tetrahydro-6-methyl-2H-isoindole-1,3-dione (3b)
Ph
Ph
Me
N
Me
Ph
Ph
OH
N
O
11
10Me
7
Br
Me
6
8
9
1
O
N
3
N
5
1j
3i
Me
4
O
aReaction conditions: 1 (0.5 mmol), 2 (1.5 mmol), PdCl2 (0.025 mmol),
dppp (0.03 mmol), Et3N (2mmol), THF (7ml), CO (10atm), 120°C, 3h.
Oil. 1H NMR (400 MHz, CDCl3) δ 1.08 (d, JHH = 6.3 Hz, 3H,
CHCH3), 1.28–1.38 (m, 1H, CH2/2), 1.74–1.92 (m, 3H, CH and
2CH2/2), 2.21–2.31 (m, 1H, CH2/2), 2.41–2.50 (m, 2H, CH2), 2.91
(s, 6H, 2CH3). 13C NMR (100 MHz, CDCl3) δ 19.88 (C11), 21.27
(C4), 27.94 (C6), 28.04 (C5), 29.59 (C7), 45.09 (C10), 139.81 (C9),
139.89 (C8), 169.70 (C1), assignments to C5–C7 are interchange-
able, assignments to C8 and C9 are interchangeable. Anal. Calcd
for C11H16N2O2: C, 63.44; H, 7.74; N, 13.45. Found: C, 63.24; H,
7.70; N, 13.33.
Conclusion
In summary, it has been shown that β-bromo-α,β-unsaturated
carboxylic acids, which are readily prepared from α-methylene-
containing ketones under the bromination conditions of
Vilsmeier–Haak reaction and subsequent oxidation, undergo
carbonylative cyclization with 2,2-dimethylhydrazine in the
presence of a palladium catalyst to give 1-(dimethylamino)-1H-
pyrrole-2,5-diones. We believe that the products prepared by
the present reaction will be used as precursors for various
valuable heterocyclic compounds. Further study of synthetic
applications to heterocycles starting from ketones is in progress.
2-(Dimethylamino)-4,5,6,7-tetrahydro-6-phenyl-2H-isoindole-1,3-dione (3c)
14
O
7
8
6
10 Me
N
13
1
11
12
N
3
5
9
Me
4
O
Oil. 1H NMR (400 MHz, CDCl3) δ 1.77–1.88 (m, 1H, CH2/2),
2.13–2.17 (m, 1H, CH2/2), 2.33–2.47 (m, 2H, CH2), 2.54–2.60
(m, 1H, CH2/2), 2.69–2.76 (m, 1H, CH2/2), 2.85–2.98 (m, 1H, CH),
2.93 (s, 6H, 2CH3), 7.21–7.28 (m, 3H, phenyl 3CH), 7.32–7.36
(m, 2H, phenyl 2CH). 13C NMR (100 MHz, CDCl3) δ 20.76 (C4),
27.62 (C5), 29.03 (C7), 39.38 (C6), 45.12 (C10), 126.85 (C12),
126.92 (C14), 128.86 (C13), 139.81 (C11), 139.82 (C9), 144.54
(C8), 169.43 (C1 and C3), assignments to C12–C14 are
interchangeable, assignments to C8, C9 and C11 are interchangeable.
Anal. Calcd for C16H18N2O2: C, 71.09; H, 6.71; N, 10.36. Found: C, 70.95;
H, 6.70; N, 10.38.
Experimental
1H and 13C NMR (400 and 100 MHz) spectra were recorded on a
Bruker Avance Digital 400 spectrometer using tetramethylsilane
as an internal standard. Melting points were determined on a
Stanford Research Inc. MPA100 automated melting point
apparatus. High-resolution mass spectrometry (HRMS) was
performed with a Jeol JMS-700 spectrometer at the Korea Basic
Science Center, Daegu, Korea. The isolation of pure products
was carried out via thin-layer (silica gel 60 GF254, Merck) or
column (silica gel 60, 70–230 mesh, Merck) chromatography.
Appl. Organometal. Chem. 2014, 28, 225–229
Copyright © 2014 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/aoc

Y. K. Bae and C. S. Cho
2-(Dimethylamino)-4,5,6,7-tetrahydrocyclohepta[c]pyrrole-1,3(2H,4H)-
dione (3d)
242.1058. Anal. Calcd for C14H14N2O2: C, 69.41; H, 5.82; N, 11.56.
Found: C, 69.32; H, 5.69; N, 11.47.
O
1
6
2
1-(Dimethylamino)-3-methyl-4-phenyl-1H-pyrrole-2,5-dione (3h)
3
5
Me
4
N
N
Me
O
1
5
Me
N
Me
6
2
3
O
N
4
8
7
9
O
Oil. 1H NMR (400 MHz, CDCl3) δ 1.64–1.70 (m, 4H, 2CH2), 1.77–1.83
(m, 2H, CH2), 2.49–2.52 (m, 4H, allylic 2CH2), 2.91 (s, 6H, 2CH3). 13
10
C
1
NMR (100 MHz, CDCl3) δ 24.67 (C3), 26.60 (C2), 30.26 (C4), 44.99
(C6), 140.93 (C5), 170.48 (C1), assignments to C2 and C3 are
interchangeable. Anal. Calcd for C11H16N2O2: C, 63.44; H, 7.74; N,
13.45. Found: C, 63.37; H, 7.70; N, 13.48.
Oil. H NMR (400 MHz, CDCl3) δ 2.19 (s, 3H, CCH3), 2.97 (s, 6H,
2CH3), 7.41–7.50 (m, 3H, phenyl 3CH), 7.55–7.58 (m, 2H, phenyl
2CH). 13C NMR (100 MHz, CDCl3) δ 10.15 (C6). 45.14 (C5), 128.80
(C8), 128.92 (C7), 129.74 (C9), 129.89 (C10), 135.19 (C2), 135.82
(C3), 169.64 (C4), 170.53 (C1), assignments to C1 and C4 are
interchangeable, assignments to C2 and C3 are interchangeable.
Anal. Calcd for C13H14N2O2: C, 67.81; H, 6.13; N, 12.17. Found: C,
67.60; H, 6.09; N, 12.11.
2-(Dimethylamino)-4,5,6,7,8,9-hexahydro-2H-cycloocta[c]pyrrole-1,3-
dione (3e)
O
1
3
2
6
5
Me
4
N
N
Me
4,5,6,7-Tetrahydro-2-(phenylamino)-2H-isoindole-1,3-dione (3j)
O
8
7
O
6
2
1
4
5
1
3
Oil. H NMR (400 MHz, CDCl3) δ 1.53–1.59 [m, 4H, ―(CH2)2―],
1.74–1.80 (m, 4H, 2CH2), 2.54–2.57 (m, 4H, allylic 2CH2), 2.91
(s, 6H, 2CH3). 13C NMR (100 MHz, CDCl3) δ 22.15 (C4), 25.72 (C3),
26.52 (C2), 45.11 (C6), 139.60 (C5), 170.64 (C1). Anal. Calcd for
C12H18N2O2: C, 64.84; H, 8.16; N, 12.60. Found: C, 64.72; H, 8.10;
N, 12.50.
N
N
H
O
Semi-solid. 1H NMR (400 MHz, CDCl3) δ 1.77–1.80 [m, 4H, ―
(CH2)2―], 2.35–2.38 (m, 4H, 2CH2), 6.10 (s, 1H, NH), 6.73–6.75
(m, 2H, phenyl 2CH), 6.89–6.93 (m, 1H, phenyl CH), 7.18–7.22
(m, 2H, phenyl 2CH). 13C NMR (100 MHz, CDCl3) δ 20.23 (C3),
21.30 (C2), 113.85 (C6), 122.05 (C8), 129.38 (C7), 140.61 (C4),
146.24 (C5), 169.23 (C1), assignments to C4 and C5 are inter-
changeable. Anal. Calcd for C14H14N2O2: C, 69.41; H, 5.82; N,
11.56. Found: C, 69.50; H, 5.80; N, 11.51.
2-(Dimethylamino)-4,5,6,7,8,9,10,11,12,13-decahydro-2H-cyclododeca[c]
pyrrole-1,3-dione (3f)
4
5
3
2
O
1
8
Me
7
6
N
N
Me
O
Acknowledgments
Oil. 1H NMR (400 MHz, CDCl3) δ 1.24–1.44 [m, 12H, ―(CH2)6―],
1.69–1.75 (m, 4H, 2CH2), 2.38–2.42 (m, 4H, allylic 2CH2), 2.91 (s, 6H,
2CH3). 13C NMR (100 MHz, CDCl3) δ 21.43 (C6), 22.28 (C5), 24.51
(C4), 25.31 (C3), 26.11 (C2), 45.12 (C8), 140.07 (C7), 170.57 (C1),
assignments to C5 and C6 are interchangeable. Anal. Calcd for
C16H26N2O2: C, 69.03; H, 9.41; N, 10.06. Found: C, 68.92; H, 9.20;
N, 10.11.
This research was supported by the Basic Science Research
Program through the National Research Foundation of Korea
(NRF) funded by the Ministry of Education, Science and Technology
(2010-0007563) and Kyungpook National University Research
Fund, 2013.
References
2-(Dimethylamino)-4,5-dihydro-2H-benzo[e]isoindole-1,3-dione (3g)
[1] H. M. Colquhoun, D. J. Thompson, M. V. Twigg, Carbonylation: Direct
Synthesis of Carbonyl Compounds, Plenum Press, New York, 1991.
[2] J. Tsuji, Palladium Reagents and Catalysis, Wiley, Chichester, 1995.
[3] Handbook of Organopalladium Chemistry for Organic Synthesis, Vol. II
(Ed.: E. Negishi), Wiley, New York, 2002.
O
3
14
4
10
11
Me
5
N
1
N
12
6
7
Me
13
[4] Modern Carbonylation Methods (Ed.: L. Kollár), Wiley-VCH, Weinheim,
2008.
O
9
8
[5] A. Brennführer, H. Neumann, M. Beller, Angew. Chem. Int. Ed. 2009,
48, 4114.
[6] R. Grigg, S. P. Mutton, Tetrahedron 2010, 66, 5515.
[7] C. S. Cho, H. S. Shim, Tetrahedron Lett. 2006, 47, 3835.
[8] H. K. Lee, C. S. Cho, Appl. Organomet. Chem. 2012, 26, 406.
[9] C. S. Cho, H. B. Kim, Catal. Lett. 2010, 140, 116.
[10] C. S. Cho, J. U. Kim, H.-J. Choi, J. Organomet. Chem. 2008, 693, 3677.
[11] C. S. Cho, H. B. Kim, S. Y. Lee, J. Organomet. Chem. 2010, 695, 1744.
[12] C. S. Cho, J. I. Son, N. S. Yoon, Appl. Organomet. Chem. 2012, 26, 499.
[13] Y. K. Bae, C. S. Cho, Synlett 2013, 24, 1848.
[14] Z. Arnold, A. Holly, Collect. Czech. Chem. Commun. 1961, 26, 3059.
[15] R. M. Coates, P. D. Senter, W. R. Baker, J. Org. Chem. 1982, 47, 3597.
[16] S. Brahma, J. K. Ray, Tetrahedron 2008, 64, 2883.
Solid. m.p. 169–170 °C. 1H NMR (400 MHz, CDCl3) δ 2.66 (t, JHH
=
8.5 Hz, 2H, benzylic CH2), 2.98 (s, 6H, 2CH3), 3.00 (t, JHH = 8.5 Hz,
2H, allylic CH2), 7.21–7.23 (m, 1H, CH), 7.25–7.34 (m, 2H, 2CH),
8.09–8.11 (m, 1H, CH). 13C NMR (100 MHz, CDCl3) δ 18.05 (C5),
27.27 (C4), 45.16 (C14), 126.18 (C8), 126.68 (C13), 127.43 (C9),
128.58 (C6), 130.71 (C7), 134.33 (C12), 136.10 (C10), 137.03
(C11), 168.60 (C1), 169.25 (C3), assignments to C1 and C3 are
interchangeable, assignments to C6–C8 are interchangeable.
HRMS (EI). Anal. Calcd for C14H14N2O2 (M+): 242.1055. Found:
wileyonlinelibrary.com/journal/aoc
Copyright © 2014 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2014, 28, 225–229

Palladium-catalyzed carbonylative cyclization
[17] R. Jana, I. Chatterjee, S. Samanta, J. K. Ray, Org. Lett. 2008, 10, 4795.
[18] P. Karthikeyan, A. Meena Rani, R. Saiganesh, K. K. Balasubramanian, S.
Kabilan, Tetrahedron 2009, 65, 811.
[19] S. Samanta, R. Jana, J. K. Ray, Tetrahedron Lett. 2009, 50, 6751.
[20] S. Nandi, J. K. Ray, Tetrahedron Lett. 2009, 50, 6993.
[21] R. Jana, S. Paul, A. Biswas, J. K. Ray, Tetrahedron Lett. 2010, 51, 273.
[22] S. Samanta, N. Yasmin, D. Kundu, J. K. Ray, Tetrahedron Lett. 2010,
51, 4132.
[26] C. S. Cho, D. B. Patel, Tetrahedron 2006, 62, 6388.
[27] C. S. Cho, H. B. Kim, J. Organomet. Chem. 2011, 696, 3264.
[28] H. K. Lee, C. S. Cho, Appl. Organomet. Chem. 2012, 26, 185.
[29] E. Deniau, D. Enders, Tetrahedron Lett. 2000, 41, 2347.
[30] H. N. Nguyen, V. J. Cee, H. L. Deak, B. Du, K. P. Faber, H. Gunaydin, B.
L. Hodous, S. L. Hollis, P. H. Krolikowski, P. R. Olivieri, V. F. Patel, K.
Romero, L. B. Schenkel, S. D. Geuns-Meyer, J. Org. Chem. 2012,
77, 3887.
[23] N. Yasmin, J. K. Ray, Synlett 2010, 924.
[24] S. Paul, T. Gorai, A. Koley, J. K. Ray, Tetrahedron Lett. 2011, 52, 4051.
[25] C. S. Cho, D. B. Patel, S. C. Shim, Tetrahedron 2005, 61, 9490.
[31] E. Dalcanali, F. Montanari, J. Org. Chem. 1986, 51, 567.
[32] K. Ichimura, S. Watanabe, K. Kusakawa, H. Ochi, Nippon Kagaku Kaishi
1980, 837.
Appl. Organometal. Chem. 2014, 28, 225–229
Copyright © 2014 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/aoc