A Practical Three-Step Synthesis of Vinylferrocene

Article abstract of DOI:10.1055/s-0036-1589142

An improved, short and efficient synthesis of vinylferrocene is reported. This three-step synthesis includes Friedel-Crafts acylation, reduction, and a one-pot mesylation/elimination step to afford the target compound in 62% yield over three steps.

Full text of DOI:10.1055/s-0036-1589142

SYNTHESIS
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©
Georg Thieme Verlag Stuttgart · New York
2017, 49, A–D
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Synthesis
K. Plevová et al.
PSP
A Practical Three-Step Synthesis of Vinylferrocene
Kristína Plevová
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3-
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5
5
1
2
. AcCl, AlCl3
. NaBH4
3
6
-step synthesis
2% yield over 3 steps
Brigita Mudráková
Radovan Šebesta*
Fe
Fe
0
0
0
0
0-
0
0
2
7-
9
7
5
3-
6
0
8
3. MsCl
scalable
vinylferrocene
Comenius University in Bratislava, Faculty of Natural
Sciences, Department of Organic Chemistry,
Mlynska dolina, Ilkovičova 6, 842 15 Bratislava, Slovakia
radovan.sebesta@uniba.sk
Received: 05.10.2017
Accepted after revision: 30.10.2017
Published online: 11.12.2017
OH
(a)
dehydration
DOI: 10.1055/s-0036-1589142; Art ID: ss-2017-t0640-psp
Fe
Fe
Fe
Abstract An improved, short and efficient synthesis of vinylferrocene
is reported. This three-step synthesis includes Friedel–Crafts acylation,
reduction, and a one-pot mesylation/elimination step to afford the tar-
get compound in 62% yield over three steps.
O
H
(b)
Wittig reaction
Fe
Key words ferrocene, Friedel–Crafts acylation, elimination, hydroami-
nation, vinylferrocene
O
H
(c)
Ferrocene and its derivatives possess a range of useful
properties, which led to their applications in catalysis, ma-
terials science, and medicine.
Petasis reagent
Fe
Fe
1–3
One of the key building
blocks for incorporation of a ferrocene moiety into target
structures is vinylferrocene. Vinylferrocene has been used
Scheme 1 Known procedures for the synthesis of vinylferrocene
4–9
in organic synthesis in Heck type reactions
and Diels–
10,11
Alder cycloadditions.
During our research on new syn-
paper, we present a multigram synthesis of vinylferrocene
from ferrocene in three steps. We also show the possible
utilization of vinylferrocene as a starting material for the
preparation of chiral ferrocenyl amines.
We started the synthesis of vinylferrocene by using
modified reaction conditions published by Bin and co-
workers.16 First, acetylferrocene was prepared by using the
well-known Friedel–Crafts acetylation protocol. Ferrocene
(1) was treated with acetyl chloride in the presence of AlCl3
as a Lewis acid, yielding the acetylferrocene (2) in 73% yield.
Reduction of 2 with NaBH4 led to the formation of hy-
droxyethylferrocene (3) in 98% yield (Scheme 2).
theses of chiral ferrocene derivatives, we needed access to
vinylferrocene in larger quantities. Even though vinylferro-
cene was first reported in the 1950s, methods for its
preparation are still not very convenient. Despite its decep-
tively simple structure, it was not easy to obtain larger
quantities of vinylferrocene in good purity. Earlier publica-
tions described the synthesis of vinylferrocene by sublima-
12–15
tion pyrolysis of the corresponding alcohol.
More re-
cent reports such as that by Bin and co-workers described
dehydration of the alcohol using copper(II) sulfate and hy-
droquinone in refluxing toluene to afford vinylferrocene
16
(
Scheme 1, a). Other approaches to vinylferrocene involve
O
OH
methylenation of ferrocenecarboxaldehyde. This method,
however, requires handling of a reactive Wittig reagent re-
sulting from methyltriphenylphosphonium bromide (Scheme
AcCl (1.05 equiv)
AlCl3 (1.1 equiv)
NaBH4 (5 equiv)
Fe
Fe
Fe
CH2Cl2
0 to r.t., 2 h
MeOH
r.t., 20 min
1
7
1
, b), or even more complex formation in situ of dimethyl-
18
titanocene Cp TiMe (Petasis reagent; Scheme 1, c).
1
2 (73%)
3 (98%)
2
2
Vinylferrocene is commercially available, but its high
price (typically higher than €100 per 1 g of vinylferrocene)
may be prohibitive for its effective use in organic synthesis.
In this context, we decided to investigate the synthesis of
vinylferrocene from simple starting materials, utilizing
easily available and conveniently handled reagents. In this
Scheme 2 Synthesis of hydroxyethylferrocene (3)
The last step of Bin’s vinylferrocene synthesis was de-
hydration of alcohol 3 with anhydrous CuSO in refluxing
toluene. In our hands, this protocol with and without a
4
©
Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–D

B
Synthesis
K. Plevová et al.
PSP
Dean–Stark trap gave unreliable results. We could isolate
desired vinylferrocene (4) in up to 35% yield (Table 1, entry
stirring of the reaction mixture at room temperature, total
conversion of starting alcohol 3 was observed and, after pu-
rification, vinylferrocene (4) was isolated in 86% yield.
With optimum reaction conditions in hand, the large-
scale synthesis was investigated. Starting from 6 grams
(26.0 mmol) of alcohol 3, we have isolated 3.85 grams (18.2
mmol, 70%) of pure vinylferrocene (4).
1). Under these conditions, ether 5 was typically obtained
as an important by-product (Scheme 3). It seems likely that
dehydration depends greatly on the reaction temperature.
Therefore, we have also tried other common dehydrating
reagents such as anhydrous Al O or SiO (Table 1). These
2
3
2
methods afforded only traces of vinylferrocene (4; Table 1,
entries 2 and 3). Neither short (few minutes) nor long reac-
tion time (48 hours) led to the successful formation of 4.
Buchwald and co-workers described a new approach to
hydroamination of non-activated alkenes using copper
hydride formed in situ followed by electrophilic hydroxyl-
amine.19 Inspired by this work, we decided to employ vinyl-
ferrocene as an alkene in the enantioselective and regio-
selective one-pot CuH-catalyzed hydroamination. In this
reaction, vinylferrocene (4) was reacted with amine 7 and
dimethoxymethylsilane (DMMS) under the catalysis of
copper(II) acetate and a suitable ligand (Scheme 4). In an
initial attempt, rac-BINAP (L1) failed to afford racemic hy-
droamination product rac-8. Eventually, we synthesized a
racemic standard of amine 8 by nucleophilic substitution.
The acetate group in 6a was replaced with the correspond-
ing amine (dibenzylamine) by stirring of these components
at room temperature overnight in acetonitrile, yielding tar-
get racemic product rac-8 in 85% yield. An enantioselective
version of the hydroamination with (R)-DTBM-SEGPHOS li-
gand (L2) afforded only traces of the desired product, amine
OH
dehydration reagent
Fe
Fe
4
solvent, temp, time
3
By-products
OPG
O
Fe
Fe
Fe
6a (PG = Ac)
6b (PG = Tf)
5
6c (PG = Ms)
Scheme 3 Dehydration of alcohol 3
8
when 2 molar equivalents of DMMS as hydride source
Table 1 Dehydration of Alcohol 3
was used. A larger amount of hydride source (4 equiv) al-
lowed isolation of target product 8 in 18% yield and with an
enantiomeric purity of 60:40 e.r. (Scheme 4). The low yield
of the hydroamination product was probably due to the for-
mation of several undesired by-products. Apart from amine
Entry Dehydrating agent Solvent
Temp
Time
Yield of 4
(
h)
(%)a
1
2
3
4
5
6
CuSO
Al
SiO
Ac O (2 equiv)
Tf O (2.4 equiv)
MsCl (1.05 equiv)
Isolated yield.
4
(5 equiv)
(10 equiv)
(10 equiv)
toluene
reflux
r.t.
1
35b
traceb
4 c
2
O
3
CH
CH
CH
CH
CH
2
2
2
2
2
Cl
Cl
Cl
Cl
Cl
2
2
2
2
2
48
48
8, we also isolated ethylferrocene (9) (isolated in 15% yield)
2
r.t.
and butane-2,3-diyldiferrocene (10) as homocoupling
product of vinylferrocene (isolated in 20% yield).
0 °C to r.t.
r.t.
2.5
0d
2
24
4
traceb
86
2
Ph
Cu(OAc)2 (6 mol%)
N
0 °C to r.t.
Ph
∗
(R)- DTBM-Segphos
a
b
c
(6.6 mol%)
Ph
N
Ph
Unreacted alcohol 3 was isolated.
Ether 5 (42%) and unreacted alcohol 3 (42%) were isolated.
Fe
+
Fe
DMMS (4 equiv)
OBz
1
M THF (anhyd)
d
The corresponding acetic acid ester was obtained in quantitative yield.
r.t.–40 °C, 24 h
4
7
8,18%
(1 equiv)
(1.2 equiv)
e.r. 60:40
O
We then focused on the transformation of the hydroxyl
t-Bu
OMe
t-Bu
function to a better leaving group, such our acetate, triflate,
or mesyl group (Scheme 1). Ideally, this leaving group
would be labile enough to eliminate spontaneously to af-
ford vinylferrocene. The corresponding acetate (6a) was
formed with acetic acid anhydride in quantitative yield.
However, no formation of vinylferrocene was observed
when acetate 6a was treated with bases such as NaOH or
O
O
PAr2
PAr2
Ar =
O
(
R)-DTBM-SEGPHOS
Scheme 4 Application of vinylferrocene in Cu-catalyzed hydroamina-
tion
Et N (Table 1, entry 4). If triflic anhydride was used as pro-
In conclusion, we have developed a laboratory-friendly
synthesis of vinylferrocene in high yield (62% over three
steps). This procedure also allows multigram scale synthe-
sis and thus convenient access to larger quantities of vinyl-
ferrocene. We have also evaluated vinylferrocene as a start-
ing material for enantioselective and regioselective one-pot
3
tecting reagent, only traces of vinylferrocene and unreacted
alcohol were isolated (entry 5). A successful result was ob-
served after using mesyl chloride (entry 6). After 4 hours
©
Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–D

C
Synthesis
K. Plevová et al.
PSP
CuH-catalyzed hydroamination. Further optimization of
this protocol as a new approach to chiral ferrocenyl amines
is under way in our laboratory.
Vinylferrocene (4)
[CAS Reg. No. 1271-51-8]
Under an inert atmosphere, to a solution of alcohol 3 (2.00 g, 8.69
mmol) and DMAP (53.1 mg, 0.43 mmol) in anhydrous CH Cl (20 mL)
2
2
was added dropwise Et N (3.64 mL, 26.1 mmol) at 0 °C, followed by
3
addition of methanesulfonyl chloride (0.45 mL, 9.14 mmol). The reac-
tion mixture was then stirred at r.t. for 4 h. The reaction was
Anhydrous solvents were freshly distilled (CH Cl from CaH , THF
2
2
2
1
13
from Na/benzophenone). H and C NMR spectra were recorded at
1
13
quenched by addition of 5% solution of NaHCO (40 mL), and the mix-
6
00 or 300 MHz for H nuclei, 150 or 75 MHz for C nuclei. Chemical
3
ture was extracted with CHCl (3 × 100 mL). Collected organic layers
shifts are reported in δ units, parts per million (ppm); signals are ref-
erenced to TMS as internal standard. Coupling constants (J) are given
in Hz and multiplicity is abbreviated as: s (singlet), br s (broad sin-
glet), d (doublet), dd (doublet of doublets), t (triplet), q (quartet), m
3
were washed with brine (100 mL), dried over Na SO , filtrated, and
2
4
solvent was removed under reduced pressure to afford the crude
2
product. The crude product was purified by chromatography on Al O3
(
hexanes/EtOAc, 9:1; R = 0.8) to afford target product 4.
(
multiplet). HRMS were measured using heated electrospray ioniza-
f
20
Yield: 1.59 g (86%); yellow-orange solid; mp 50–52 °C (lit.15 51–
52 °C).
tion (HESI). Specific optical rotations ([α]D ) values are reported in
degrees; concentration (c) is in 1 g/100 mL. Reactions were moni-
tored by thin-layer chromatography (TLC) carried out on silica or alu-
mina plates, visualized by irradiation with UV light. Commercially
available reagents were used without further purification. Synthesis
of starting materials was performed according to reported procedures
or is specified below.
IR (ATR): 1623, 1408, 1103, 1045, 998, 894, 810, 726, 517, 477, 446
–1
cm
.
1
H NMR (600 MHz, CDCl ): δ = 6.46 (dd, J = 17.4, 10.7 Hz, 1 H), 5.34 (d,
3
J = 17.5 Hz, 1 H), 5.03 (d, J = 10.7 Hz, 1 H), 4.36 (s, 2 H), 4.21 (s, 2 H),
4
.11 (s, 5 H).
1
3
Acetylferrocene (2)20
C NMR (151 MHz, CDCl ): δ = 134.7, 111.1, 83.7, 69.3, 68.7, 66.8.
3
+
+
HRMS (ESI): m/z calcd for [M + H ] C12H Fe : 213.0367; found:
2
[
CAS Reg. No. 1271-55-2]
13
13.0359.
To a solution of ferrocene (1; 5.00 g, 26.87 mmol) in anhydrous CH Cl2
2
Obtained spectral data are in agreement with those of the commer-
cially available product.
(
(
30 mL), a solution of acetyl chloride (2.01 mL, 28.21 mmol) and AlCl3
3.94 g, 29.55 mmol) in anhydrous CH Cl (40 mL) was added at 0 °C.
2
2
The reaction temperature was allowed to rise to r.t., and the dark-vio-
let solution was stirred for 2 h. The reaction was quenched by addi-
tion of ice-cold water (70 mL) at 0 °C and the mixture was extracted
1-(Ferrocen-3-yl)ethyl Acetate (6a)22
To a solution of alcohol 3 (1.00 g, 4.30 mmol) in CH Cl (6 mL) was
2
2
with CH Cl (3 × 70 mL). The collected organic layers were washed
2
2
added dropwise Et N (1.21 mL, 8.70 mmol) at 0 °C, followed by slow
3
with a solution of Na CO (50 mL), dried over Na SO , filtrated and the
2
3
2
4
dropping of a solution of Ac O (0.82 mL, 8.70 mmol) and DMAP (26.5
2
solvent was removed under reduced pressure. Crude product (dark-
orange solid) was purified by chromatography on SiO2 (hexanes/
mg, 0.21 mmol) in CH Cl (3 mL). The reaction mixture was then
2
2
stirred at r.t. for 2.5 h. The reaction was quenched by addition of satu-
rated Na CO (15 mL) and the mixture was extracted with CH Cl2
EtOAc = 4:1; R = 0.3) to afford target product 2.
f
2
3
2
Yield: 4.45 g (73%); orange solid; mp 85–86 °C (lit.20 85–86 °C).
(3 × 30 mL). Collected organic layers were washed with brine (50 mL),
dried over Na SO , filtrated and solvent was removed under reduced
1
2
4
H NMR (300 MHz, CDCl ): δ = 4.78–4.76 (m, 2 H), 4.55–4.42 (m, 2 H),
3
pressure to afford the crude product. Isolated acetate 6a was charac-
terized and used in subsequent reaction without further purification.
Yield: 1.16 g (quant.); orange solid; mp 68–70 °C (lit.22 67–68 °C).
4
.20 (s, 5 H), 2.40 (s, 3 H).
NMR spectra are in agreement with those of the commercially avail-
able product.
1
H NMR (600 MHz, CDCl ): δ = 5.83 (q, J = 6.5 Hz, 1 H), 4.27–4.26 (m,
3
α-Methylferrocenemethanol (3)21
1 H), 4.22–4.22 (m, 1 H), 4.17–4.15 (m, 2 H), 4.15 (s, 5 H), 2.03 (s, 3 H),
1.56 (d, J = 6.5 Hz, 3 H).
[
CAS Reg. No. 1277-49-2]
To a solution of acetylferrocene (2; 3.00 g, 13.15 mmol) in MeOH (75
O-Benzoyl-N,N-dibenzylhydroxylamine (7)23
mL), solid NaBH (2.49 g, 65.77 mmol) was added in one portion at r.t.
4
Product 7 was prepared according a reported procedure; mp 97–99 °C
(CAUTION: very exothermic reaction). The reaction mixture was
23
(
lit 96–98 °C).
stirred at r.t. for 20 min. Formed solution was poured into ice-cold
water (100 mL) and extracted with CH Cl (3 × 100 mL). The collected
2
2
rac-N,N-Dibenzyl-1-(ferrocenyl)ethan-1-amine (rac-8)
organic layers were washed with brine (100 mL), dried over Na SO ,
2
4
filtrated, and solvent was removed under reduced pressure to afford
the crude product. Isolated alcohol 3 was characterized and used in
subsequent reaction without further purification.
To a solution of acetate 6a (200 mg, 0.73 mmol) in MeCN (10 mL) was
dropwise added dibenzylamine (0.28 mL, 1.46 mmol) at r.t. and the
mixture was stirred overnight (20 h). The reaction was quenched by
2
addition of H O (15 mL) and the mixture was extracted with CHCl3
Yield: 2.97 g (98%); yellow-orange solid; mp 75–77 °C.
(
3 × 25 mL). The collected organic layers were washed with brine (25
mL), dried over Na SO , filtrated and solvent was removed under re-
duced pressure to afford the crude product. Crude product was puri-
1
H NMR (300 MHz, CDCl ): δ = 4.59–4.51 (m, 1 H), 4.23–4.16 (m, 9 H),
3
2
4
1.83 (d, J = 4.8 Hz, 1 H), 1.44 (d, J = 6.4 Hz, 3 H).
NMR spectra are in agreement with those of the commercially avail-
able product.
fied by chromatography on SiO (hexanes/EtOAc, 10:1 + 1% Et N; R =
0.8) to afford target product rac-8.
2
3
f
Yield: 235 mg (85%); orange solid.
©
Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–D

D
Synthesis
K. Plevová et al.
PSP
Procedure for Enantiomerically Enriched N,N-Dibenzyl-1-(ferro-
cenyl)ethan-1-amine [(S)-8]
Supporting Information
Supporting information for this article is available online at
https://doi.org/10.1055/s-0036-1589142.
In anhydrous THF (1 mL) was dissolved 6 mol% Cu(OAc)2 (10.9 mg,
S
u
p
p
o
nrtogI
i
f
rm oaitn
S
u
p
p
ortioIgnfmr oaitn
0.066 mmol) and 6.6 mol% of ligand (R)-DTBM-SEGPHOS (78 mg,
0.060 mmol). The mixture was stirred for 15 min at r.t., then DMMS
(
0.5 mL, 4 equiv, 4 mmol) was added dropwise and stirring was con-
tinued for 10 min at the same temperature. The solution of amine 7
381 mg, 1.2 mmol) and vinylferrocene 4 (212 mg, 1 mmol) was then
References
(
(1) Togni, A.; Hayashi, T. Ferrocenes; Wiley-VCH: Weinheim, 1995.
added by using Schlenk techniques to the tube containing the solu-
tion of [L*CuH] complex. The reaction mixture was stirred at 40 °C
overnight, then the mixture was diluted with EtOAc (5 mL) and 5%
solution of Na CO (5 mL) was added dropwise. The solution was ex-
tracted with EtOAc (3 × 25 mL), the collected organic layers were
washed with brine (25 mL), dried over Na SO , filtrated, and the sol-
vent was removed under reduced pressure to afford the crude prod-
uct. The crude product was purified by chromatography on SiO (hex-
anes/EtOAc, 30:1 + 1% Et N; R = 0.4) to afford target product 8.
(2) Štepnička, P. Ferrocenes: Ligands, Materials and Biomolecules;
Wiley: Chichester, 2008.
(3) Dai, L.-X.; Hou, X.-L. Chiral Ferrocenes in Asymmetric Catalysis;
Wiley-VCH: Weinheim, 2010.
2
3
(4) Amatore, C.; Gazard, S.; Maisonhaute, E.; Pebay, C.; Schöllhorn,
B.; Syssa-Magalé, J.-L.; Wadhawan, J. Eur. J. Inorg. Chem. 2007,
2
4
4035.
2
(
5) Kowalski, K.; Koceva-Chyła, A.; Szczupak, Ł.; Hikisz, P.;
Bernasińska, J.; Rajnisz, A.; Solecka, J.; Therrien, B. J. Organomet.
Chem. 2013, 741–742, 153.
3
f
20
Yield: 68 mg (18%); orange solid; mp 62–65 °C; [α]
CHCl ); HPLC analysis (Chiralcel OD-H; hexane/ PrOH, 99:1; 0.8
mL/min; 254 nm) indicated 20% ee: t = 5.9 (major), 6.5 (minor) min.
–14.5 (c 1.00,
D
i
3
(6) Suárez-Meneses, J. V.; Bonilla-Reyes, E.; Blé-González, E. A.;
Ortega-Alfaro, M. C.; Toscano, R. A.; Cordero-Vargas, A.; López-
Cortés, J. G. Tetrahedron 2014, 70, 1422.
(7) Bolisetty, M. N. K. P.; Li, C.-T.; Thomas, K. R. J.; Bodedla, G. B.; Ho,
K.-C. Tetrahedron 2015, 71, 4203.
R
IR (ATR): 1234, 1103, 1068, 1022, 998, 822, 749, 728, 697, 514, 487
cm
–1
.
1
H NMR (600 MHz, CDCl ): δ = 7.39 (d, J = 7.4 Hz, 4 H, -Ph), 7.31 (t, J =
3
(
8) Baartzes, N.; Stringer, T.; Seldon, R.; Warner, D. F.; de Kock, C.;
Smith, P. J.; Smith, G. S. J. Organomet. Chem. 2016, 809, 79.
9) Stringer, T.; De Kock, C.; Guzgay, H.; Okombo, J.; Liu, J.;
Kanetake, S.; Kim, J.; Tam, C.; Cheng, L. W.; Smith, P. J.;
Hendricks, D. T.; Land, K. M.; Egan, T. J.; Smith, G. S. Dalton
Trans. 2016, 13415.
7
.6 Hz, 4 H, -Ph), 7.23 (t, J = 7.3 Hz, 2 H, -Ph), 4.27–4.27 (m, 1 H, Fc),
Fc
4
3
1
.18–4.14 (m, 3 H, Fc), 4.02 (s, 5 H, Cp ), 3.81 (q, J = 6.9 Hz, 1 H, H ),
α
(
.53 (d, J = 14.1 Hz, 2 H, CH -Ph), 3.36 (d, J = 14.1 Hz, 2 H, -CH -Ph),
2
2
.47 (d, J = 6.9 Hz, 3 H, -CH3).
1
3
Ph
C NMR (151 MHz, CDCl ): δ = 140.9 (2×C, Cq ), 128.6 (4×C, -Ph),
3
Fc
Fc
1
28.2 (4×C, -Ph), 126.7 (2×C, -Ph), 88.9 (Cq ), 69.1 (-CH ), 68.7 (5×C,
(10) Lai, H.-W.; Liu, Z.-Q. Eur. J. Med. Chem. 2014, 81, 227.
Fc
Fc
Fc
Fc
Cp ), 67.6 (-CH ), 67.1 (-CH ), 66.9 (-CH ), 52.3 (2×C, -CH -Ph), 52.2
2
(11) Wiles, A. A.; Zhang, X.; Fitzpatrick, B.; Long, D.-L.; Macgregor, S.
A.; Cooke, G. Dalton Trans. 2016, 7220.
(12) Arimoto, F. S.; Haven, A. C. J. Am. Chem. Soc. 1955, 77, 6295.
(13) Schlögl, K.; Mohar, A. Naturwissenschaften 1961, 48, 376.
(-CH ), 15.4 (-CH ).
α
3
+
+
HRMS (ESI): m/z calcd for [M + H ] C26H28FeN : 410.1571; found:
10.1565.
4
(14) Buell, G. R.; McEwen, W. E.; Kleinberg, J. J. Am. Chem. Soc. 1962,
8
4, 40.
Butane-2,3-diyldiferrocene (10)
(
(
15) Rausch, M. D.; Siegel, A. J. Organomet. Chem. 1968, 11, 317.
16) Shi, R.; Wang, H.; Tang, P.; Bin, Y. Front. Chem. Sci. Eng. 2014, 8,
1
Fc
H NMR (600 MHz, CDCl ): δ = 4.09 (s, 5 H, Cp ), 4.07 (br s, 2 H, Fc),
.05 (s, 5 H, Cp ), 3.99 (br s, 2 H, Fc), 3.94 (br s, 1 H, Fc), 3.85 (br s, 1 H,
3
Fc
4
1
71.
Fc), 3.74 (br s, 1 H, Fc), 2.63–2.59 (m, 2 H, H ), 1.15 (d, J = 6.6 Hz, 3 H,
α
(
17) Carberry, J.; Irvin, J. A.; Glatzhofer, D. T.; Nicholas, K. M.; Neef, C.
-
CH ), 1.05 (d, J = 6.6 Hz, 3 H, -CH ).
3
3
J. React. Funct. Polym. 2013, 73, 730.
1
3
Fc
Fc
Fc
C NMR (151 MHz, CDCl ): δ = 93.8 (Cq ), 92.6 (Cq ), 68.8 (-CH ),
3
(18) Singh, J.; Ghosh, S.; Deb, M.; Elias, A. J. J. Organomet. Chem. 2016,
18, 85.
Fc
Fc
Fc
Fc
Fc
6
6
8.8 (5×C, Cp ), 68.4 (5×C, Cp ), 68.1 (-CH ), 67.0 (-CH ), 66.9 (-CH ),
6.8 (-CH ), 66.7 (-CH ), 66.6 (-CH ), 66.4 (-CH ), 40.9 (-CH ), 40.8
8
Fc
Fc
Fc
Fc
α
(19) Zhu, S.; Niljianskul, N.; Buchwald, S. L. J. Am. Chem. Soc. 2013,
135, 15746.
(
-CH ), 16.3 (-CH ), 14.3 (-CH ).
α 3 3
(20) Graham, P. J.; Lindsey, R. V.; Parshall, G. W.; Peterson, M. L.;
Whitman, G. M. J. Am. Chem. Soc. 1957, 79, 3416.
Funding Information
(21) Neshvad, G.; Roberts, R. M. G.; Silver, J. J. Organomet. Chem.
982, 236, 237.
(22) Hill, E. A.; Gross, M. L.; Stasiewicz, M.; Manion, M. J. Am. Chem.
Soc. 1969, 91, 7381.
1
This work was supported by the Slovak Research and Development
Agency under the contract No. APVV-0321-12.Solv
ak
Research
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(23) Berman, A. M.; Johnson, J. S. J. Org. Chem. 2006, 71, 219.
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Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–D