Synthesis and catalytic activity of an electron-deficient copper-ethylene triazapentadienyl complex

Article abstract of DOI:10.1039/b911981g

The copper(i) ethylene complex [N{(C₃F₇)C(Dipp)N} ₂]Cu(C₂H₄) (Dipp = 2,6-diisopropylphenyl) has been synthesized by treating [N{(C₃F₇)C(Dipp)N} ₂]Cu(NCCH₃)

Full text of DOI:10.1039/b911981g

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www.rsc.org/dalton | Dalton Transactions
Synthesis and catalytic activity of an electron-deficient copper–ethylene
triazapentadienyl complex†
Jaime A. Flores,a Vivek Badarinarayana,a Shreeyukta Singh,a Carl J. Lovely*a and H. V. Rasika Dias*b
Received 18th June 2009, Accepted 24th June 2009
First published as an Advance Article on the web 24th July 2009
DOI: 10.1039/b911981g
The copper(I) ethylene complex [N{(C3F7)C(Dipp)N}2]Cu(C2H4) (Dipp = 2,6-diisopropylphenyl) has
been synthesized by treating [N{(C3F7)C(Dipp)N}2]Cu(NCCH3) with ethylene at room temperature.
[N{(C3F7)C(Dipp)N} ]Cu(C2H4) is an air stable, yellow solid. X-Ray crystallographic data of
[N{(C3F7)C(Dipp)N}22]Cu(C2H4) show that the 1,3,5-triazapentadienyl ligand coordinates to copper in
2
k -fashion. The copper atom adopts a trigonal-planar geometry. [N{(C3F7)C(Dipp)N}2]Cu(C2H4) and
[N{(C3F7)C(Dipp)N}2]Cu(NCCH3) effectively catalyze carbene and nitrene transfer to a variety of
substrates in high efficiencies.
Introduction
There has been a considerable amount of interest in the synthesis
and catalytic properties of nitrogen based ligand supported
transition metal complexes, in particular those containing flu-
orinated analogs of the venerable tris(pyrazoyl)borate ligand.1–7
For example, ligands such as [HB(3,5-(CF3)2Pz)3]-, in addition
to permitting the stabilization of a variety of unusual complexes
of the coinage metals, support silver adducts such as [HB(3,5-
(CF3)2Pz)3]Ag(THF) and [HB(3,5-(CF3)2Pz)3]Ag(C2H4) that have
been shown to catalyze a variety of carbene transfer reactions, in-
cluding the formation and rearrangement of halonium ylides.1,8–13
As a continuation of this effort, we have recently reported the
preparation and some coordination chemistry of highly fluori-
nated 1,3,5-triazapentadienyl (TAP) ligands,14–17 a closely related
analogs of the popular 1,5-diazapentadienyl (b-diketiminate)
systems. While the chemistry of 1,5-diazapentadienyl systems have
been widely investigated,18 the same is not true of the metal adducts
of triaza analogs,1,19–30 and as far as we are aware, there is only
one note of the use of fluorinated triazapentadienyl complexes as
catalysts.14 Herein, we report the synthesis and characterization
of an easily isolable copper–ethylene complex, and its utility as a
group transfer catalyst.
Fig.
1
1,3,5-Triazapentadienyl complexes of copper, [N{(C3F7)C-
(Dipp)N}2]CuL (L = NCCH3 (1), C2H4 (2)).
ligand [N{(C3F7)C(Dipp)N}2]Li and CuOTf and ethylene.
[N{(C3F7)C(Dipp)N}2]Cu(C2H4) is an air stable, yellow solid. 1H
and 13C NMR signals of copper(I)-coordinated ethylene in CDCl3
appear at 3.37 and 86.0 ppm, respectively (cf . for free ethylene 1H
and 13C signals at 5.40 and 123.3 ppm, respectively).
A number of well authenticated copper(I)–ethylene adducts
are known.9 [HC{(Me)C(2,6-Me2C6H3)N}2]Cu(C2H4) represents
a three-coordinate copper–ethylene adduct supported by a
1,5-diazapentadienyl ligand.31 The ethylene 13C NMR signal in this
adduct was observed at d 74.7 ppm. In general, up-field shift of
ethylene carbons in diamagnetic metal adducts has been attributed
to the increased shielding caused by the metal-to-ethylene p-
back-donation.32–34 Thus [N{(C3F7)C(Dipp)N}2]Cu(C2H4), with
an ethylene 13C NMR signal at 86.0 ppm, displays relatively less
Cu→ethylene p-backbonding. This is not suprising considering
the presence of two fluoroalkyl groups and an extra nitrogen atom
on the ligand backbone of the [N{(C3F7)C(Dipp)N}2]Cu(C2H4).
Addition of an excess of ethylene to CDCl3 solutions of
[N{(C3F7)C(Dipp)N}2]Cu(C2H4) yielded two sharp signals at
5.40 ppm (for free ethylene) and 3.37 ppm (coordinated ethylene
in [N{(C3F7)C(Dipp)N}2]Cu(C2H4)), indicating no observable
ethylene exchange on the NMR time scale at the room temper-
ature. However with [N{(C3F7)C(2,6-Cl2C6H3)N}2]Cu(C2H4) and
[N{(C3F7)C(C6F5)N}2]Cu(C2H4), a similar experiment led to the
coalescence of the bound ethylene signal.14,15
Results and discussion
The copper(I) ethylene complex [N{(C3F7)C(Dipp)N}2]Cu(C2H4)
(2) was prepared by treating [N{(C3F7)C(Dipp)N}2]Cu(NCCH3)
(1)17 with ethylene at room temperature (Fig. 1). Alter-
natively, [N{(C3F7)C(Dipp)N}2]Cu(C2H4) can also be syn-
thesized using the lithium salt of the triazapentadienyl
aDepartment of Chemistry and Biochemistry, The University of Texas at
Arlington, Arlington, TX 76019. E-mail: lovely@uta.edu; Fax: 817-272-
3808; Tel: 817-272-5446
bDepartment of Chemistry and Biochemistry, The University of Texas at
Arlington, Arlington, TX 76019. E-mail: dias@uta.edu; Fax: 817-272-3808;
Tel: 817-272-3813
† Electronic supplementary information (ESI) available: Additional ex-
perimental details and figures. CCDC reference number 726152 (2). For
ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/b911981g
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Table 1 Products and yields from atom transfer reactions catalyzed by
copper complexes 1 and 2 (experimental details given in ESI†)
Treatment of CDCl3 solutions of [N{(C3F7)C(Dipp)N}2]-
Cu(C2H4) with CO at room temperature led to quantitative
formation of [N{(C3F7)C(Dipp)N}2]CuCO,17 as evident from
Product yielda (%)
1
the disappearance of the ethylene signal in the H NMR spec-
1b
2b
trum and the appearance of 1H NMR signals corresponding
to [N{(C3F7)C(Dipp)N}2]CuCO. The formation of the Cu–CO
adduct was further confirmed by IR spectroscopy (nCO band at
2109 cm-1). This process is reversible. It is possible to obtain
[N{(C3F7)C(Dipp)N} ]Cu(C2H4) by treating a CDCl3 solution of
[N{(C3F7)C(Dipp)N}22]CuCO with an excess of ethylene.
Entry
1
Substrate
Product
98
96
2
3
76
76
Crystals of [N{(C3F7)C(Dipp)N}2]Cu(C2H4) which were sub-
jected to X-ray crystallography, exhibited twinning, but this issue
was resolved satisfactorily. The resulting X-ray crystal structure
is illustrated in Fig. 2. The basic features are similar to those ob-
served for [N{(C3F7)C(C6F5)N}2]Cu(C2H4) and [HC{(Me)C(2,6-
Me2C6H3)N}2]Cu(C2H4).15,31 The 1,3,5-triazapentadienyl ligand
97 (1.6)c
93 (1.6)c
2
4
5
85
85
90
91
coordinates to copper in k -fashion. The copper atom adopts
a trigonal planar geometry. The average Cu–N, average Cu–C
=
and C C distances of [HC{(Me)C(2,6-Me2C6H3)N}2]Cu(C2H4)
and [N{(C3F7)C(Dipp)N}2]Cu(C2H4) are 1.912(2), 1.989(2),
˚
˚
1.365(3) A and 1.9404(9), 1.9999(11), 1.3518 (14) A, respectively.
6
7
80
85
93
~100
8
9
94
98
92
98
a The yields correspond to chromatographically purified materials and are
the average of at least two independent runs. b The reactions shown in
entries 1, 2, 3, 8 and 9 are conducted with 5 mol% of 1 or 2 while the
others (entries 4–7) were run at 2 mol% of the catalyst. c Cis : trans ratio
determined by 1H NMR spectroscopy.
Fig. 2 Molecular structure of [N{(C3F7)C(Dipp)N}2]Cu(C2H4) (2). Se-
◦
˚
lected distances (A) and angles ( ): Cu(1)–N(1) 1.9403(9), Cu(1)–N(3)
1.9406(9), Cu(1)–C(34) 1.9974(11), Cu(1)–C(33) 2.0006(11), C(33)–C(34)
1.3518(14); N(1)–Cu(1)–N(3) 95.55(4), C(34)–Cu(1)–C(33) 39.52(4).
Similarly, the combination of catalysts 1 or 2 with EDA resulted
in carbene insertion into O–H bonds of alcohols (entries 4 and
5, Table 1), N–H bonds of amines (entries 6 and 7, Table 1), and
C–H bonds of ethers, all of which proceed in excellent chemical
yields (entries 8 and 9, Table 1).6,36,40–44
Catalytic properties of metal adducts of fluorinated triaza-
pentadienyl ligands have not been explored in detail. Therefore
we wished to establish whether [N{(C3F7)C(Dipp)N}2]Cu(C2H4)
(2) would function as an atom transfer catalyst as this would
provide a platform for further developments of this unique
scaffold. In addition, the corresponding acetonitrile complex
[N{(C3F7)C(Dipp)N}2]Cu(NCCH3) (1) was investigated for com-
parative purposes.
Conclusions
Fluorinated 1,3,5-triazapentadienyl supporting ligand [N{(C3F7)-
C(Dipp)N}2]- allows the isolation of a thermally stable copper(I)
ethylene complex [N{(C3F7)C(Dipp)N}2]Cu(C2H4) in good yield.
[N{(C3F7)C(Dipp)N}2]Cu(C2H4) and the related acetonitrile ana-
log [N{(C3F7)C(Dipp)N}2]Cu(NCCH3) function as effective car-
bene and nitrene transfer catalysts on treatment with ethyl
Initial experiments were conducted with the nitrene precursor,
35–38
=
TsN IPh, and two alkene substrates styrene and cyclooctene.
Gratifyingly both complexes effect nitrene transfer, providing
the corresponding aziridines in excellent yield (entries 1 and 2,
Table 1). It was also found that on reaction of styrene with ethyl
diazoacetate (EDA), both complexes serve as carbene transfer
agents providing the expected cyclopropane as a diastereomeric
mixture (entry 3, Table 1), favoring the cis-isomer (1.6 : 1).39
=
diazoacetate or TsN IPh, respectively. These reactions proceed
in excellent yields and in the case of carbene transfer this occurs
with minimal carbene dimerization, a common by-product in these
reactions.
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the mixture stirred for further 5 min. It was filtered through a bed
of Celite, the filtrate was collected and the solvents were removed
under reduced pressure to yield [N{(C3F7)C(Dipp)N}2]Cu(C2H4)
as a yellow powder (0.21 g, 80%).
Experimental
General procedures
All manipulations were carried out under an atmosphere of
purified nitrogen using standard Schlenk techniques or in a
Drybox. Solvents were purchased from commercial sources,
purified using Innovative Technology SPS-400 PureSolv solvent
drying system or by distilling over conventional drying agents
and degassed by the freeze–pump–thaw method prior to use.
Glassware was oven-dried at 150 ◦C overnight. NMR at 25 ◦C
on a JEOL Eclipse 500 and 300 spectrometers (1H: 500.16 MHz
or 300.53 MHz; 13C: 125.77 MHz or 75.57 MHz; 19F: 470.62 MHz
or 282.78 MHz). Proton and carbon chemical shifts are reported
in ppm vs. Me4Si. 19F NMR chemical shifts were referenced
relative to external CFCl3. Elemental analyses were performed
using a Perkin Elmer Series II CHNS/O analyzer. Melting
points were obtained on a Mel-Temp II apparatus and were
not corrected. (CuOTf)2·benzene, n-butyllithium, ethylene, ethyl
X-Ray crystallographic data
A suitable crystal covered with a layer of cold hydrocarbon oil
was selected and mounted with paratone-N oil in a cryo-loop
and immediately placed in the low-temperature nitrogen stream.
The X-ray intensity data were measured at 100(2) K on a Bruker
SMART APEX CCD area detector system equipped with a
Oxford Cryosystems 700 Series cooler, a graphite monochromator,
˚
and a Mo-Ka fine-focus sealed tube (l = 0.710 73 A). The
crystals show twinning, but it was resolved satisfactorily using
Cell_Now (two cell domains with the second domain rotated from
first domain by 180◦ degrees about the reciprocal axis (-0.093
0.000 1.000) and real axis (0.000 0.000 1.000)). The data frames
were integrated with the Bruker SAINT-Plus software package.
Data were corrected for absorption effects using the multi-scan
technique (SADABS). Structures were solved and refined using
the Bruker SHELXTL (Version 6.14) software package. All the
non hydrogen atoms were refined anisotropically. Hydrogen atoms
were placed at calculated positions and refined riding on the
corresponding carbons.
˚
diazoacetate and silica gel, 200–400 mesh, 60 A were purchased
from commercial sources. [N{(C3F7)C(Dipp)N}2]H (Dipp = 2,6-
diisopropylphenyl),17 [N{(C3F7)C(Dipp)N}2]Cu(NCCH3)17 and
N-(p-toluenesulfonyl)phenyliodinane45 were synthesized using
published procedures.
[N{(C3F7)C(Dipp)N}2]Cu(C2H4). [N{(C3F7)C(Dipp)N}2]Cu-
(NCCH3) (0.10 g, 0.12 mmol) was dissolved in n-hexane (15 mL)
and C2H4 was bubbled into the solution for about 3 min. After
stirring for 1 h under C2H4 atmosphere, the solvent was removed
in several steps using reduced pressure and an ethylene stream to
assure the removal of acetonitrile from the solution without losing
the coordinated ethylene. The resulting residue was then dissolved
in CH2Cl2–n-hexane (1 : 3) (4 mL) and cooled to -20 ◦C to obtain
needle shaped crystals of [N{(C3F7)C(Dipp)N}2]Cu(C2H4). Yield:
0.084 g (85%). Mp: darkens at 120 ◦C and melts completely at
155 ◦C. 19F NMR (CDCl3): d -80.36 (triplet, 6F, JFF = 10.1 Hz,
CF3), -105.59 (quartet, 4F, JFF = 10.1 Hz, a-CF2), -121.90 (s, 4F,
Crystal data: C34H38CuF14N3, monoclinic, P21/n, 100 K; a =
◦
˚
10.4857(4), b = 23.4593(9), c = 14.9020(6) A, b = 97.622(1) , V =
3
˚
3633.3(2) A , Z = 4; R1, wR2 (I > 2s(I)) = 0.0431, wR2 = 0.0643,
GOOF = 1.031.
General procedure for nitrene transfer reactions with catalysts
[N{(C3F7)C(Dipp)N}2]CuL (L = NCCH3 or C2H4) and
N-(p-toluenesulfonyl)phenyliodinane
Aziridination of alkenes. A solution of alkene (0.5 mmol of
styrene or cyclooctene) and N-(p-toluensulfonyl)phenyliodinane
(0.5 mmol) were stirred in acetonitrile (1 mL) at room temperature
for 2 min. The catalyst (5 mol%) was added at once, and the
resulting mixture was stirred at room temperature overnight.
C6Me6 (0.0275 mmol, 4.5 mg) was added as the internal standard.
The reaction mixture was diluted with CH2Cl2 (25 mL), filtered
through a short plug of Celite and concentrated under reduced
pressure. The mixture was subjected to flash chromatography
(SiO2, hexanes–ethyl acetate (9 : 1)) and the eluent concen-
trated to dryness. The yields were estimated using 1H NMR
spectroscopy by integration of product resonances relative to
the internal standard. The NMR data of the products (N-(p-
toluenesulfonyl)-2-phenylaziridine46–48 and N-(p-toluenesulfonyl)-
9-azabicyclo[6.1.0]nonane48,49) have been reported previously (and
are given in the ESI†).
1
b-CF2). H NMR (CDCl3): d 7.09 (s, 6H, m,p-Ar), 3.37 (s, 4H,
C2H4), 2.94 (septet, 4H, JHH = 6.9 Hz, CH), 1.21 (d, 12H, JHH
=
1
6.9 Hz, CH3), 1.12 (d, 12H, JHH = 6.9 Hz, CH3). 13C{ H} NMR
(CDCl3): (selected) d 86.0 (s, C2H4). 19F NMR (C6D6): d -80.34
(t, 6F, JFF = 10.9 Hz, CF3), -105.16 (quartet, 4F, JFF = 10.9 Hz,
1
a-CF2), -121.46 (s, 4F, b-CF2). H NMR (C6D6): d 6.98 (s, 6H,
m,p-Ar), 3.26 (s, 4H, C2H4), 3.11 (septet, 4H, JHH = 6.9 Hz, CH),
1.21 (d, 12H, JHH = 6.9 Hz, CH3), 1.05 (d, 12H, JHH = 6.9 Hz,
1
CH3). 13C NMR (C6D6): (selected) d 86.1 (t, JCH = 158 Hz,
C2H4). Anal. Calc. for C34H38N3F14Cu: C, 49.91; H, 4.68; N, 5.14.
Found: C, 49.54; H, 4.81; N, 5.06%.
[N{(C3F7)C(Dipp)N}2]Cu(C2H4) can also be synthesized using
the lithium salt of the triazapentadiene ligand. n-Butyllithium
(0.2 mL, 1.6 M in hexanes) was added dropwise to a n-hexane
(25 mL) solution of [N{(C3F7)C(Dipp)N}2]H (0.233 g, 0.32 mmol)
at -78 ◦C. After the addition, the reaction mixture was allowed to
warm slowly to room temperature and stirred for further 2 h. The
solvent was removed under reduced pressure to obtain a white
solid. It was dissolved in CH2Cl2 (10 mL) and then transferred
via a cannula to a flask containing (CuOTf)2·benzene (0.081 g,
0.16 mmol). Ethylene (1 atm) was bubbled into this mixture for
about 1 min. The mixture was then stirred at room temperature
for 1 h under a C2H4 atmosphere. n-Hexane (5 mL) was added and
General procedure for carbene transfer reactions with catalysts
[N{(C3F7)C(Dipp)N}2]CuL (L = NCCH3 or C2H4) and ethyl
diazoacetate
Cyclopropanation of styrene. The catalyst (0.025 mmol,
5 mol%) and styrene (0.45 mL, ~4 mmol) were dissolved in
CH2Cl2 (8.5 mL) and stirred for 3 min. Ethyl diazoacetate (0.057 g,
0.5 mmol) in CH2Cl2 (5 mL) was added to this mixture solution by
automatic syringe over a period of ~2 h. The resulting solution was
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stirred overnight at room temperature, filtered through a short plug
of Celite, the solvent evaporated and the residue was purified by
flash chromatography on SiO2 (hexanes–ethyl ether (9 : 1)) yielding
the desired product as a colourless oil. The yield was calculated
based on the weight of the isolated and purified product, ethyl
2-phenylcyclopropane-1-carboxylate50,51 (see ESI† for NMR
data).
thank Dr Charles Campana (Bruker AXS) for his assistance with
the twinning issue of compound 2.
Notes and references
1 H. V. R. Dias and C. J. Lovely, Chem. Rev., 2008, 108, 3223–3238, and
references therein.
2 C. Pettinari, Scorpionates II: Chelating Borate Ligands, Imperial
College Press, London, 2008.
O–H insertion in alcohols. Ethyl diazoacetate (0.057 g,
0.5 mmol) dissolved in CH2Cl2 (5 mL) was added by an automatic
syringe over a period of ~2 h to a stirred solution of the catalyst
(0.010 mmol, 2 mol%) and alcohol (1 mmol of 1-propanaol or
2-propanol) in CH2Cl2 (9 mL). The resulting mixture was stirred
overnight at room temperature. C6Me6 (0.0275 mmol, 4.5 mg)
was added as the internal standard. The mixture was filtered
through a short plug of Celite and the solvent evaporated to
dryness. The residue was purified by flash chromatography on
SiO2 (hexanes–ethyl acetate (9 : 1)) and the eluent concentrated to
dryness. The yields were estimated using 1H NMR spectroscopy by
integration of product resonances relative to the internal standard.
The NMR data of the products (ethyl propoxyacetate42 and ethyl
isopropoxyacetate42) have been reported previously (and are given
in the ESI section).
3 C. Pettinari and C. Santini, Compr. Coord. Chem. II, 2004, 1, 159–210.
4 H. V. R. Dias, R. M. G. Rajapakse, D. M. M. Krishantha, M. Fianchini,
X. Wang and R. L. Elsenbaumer, J. Mater. Chem., 2007, 17, 1762–1768.
5 H. V. R. Dias, X. Wang, R. M. G. Rajapakse and R. L. Elsenbaumer,
Chem. Commun., 2006, 976–978.
6 M. M. Diaz-Requejo and P. J. Perez, Chem. Rev., 2008, 108, 3379–3394.
7 D. Diaconu, Z. Hu and S. M. Gorun, J. Am. Chem. Soc., 2002, 124,
1564–1565.
8 H. V. R. Dias and M. Fianchini, Comments Inorg. Chem., 2007, 28,
73–92.
9 H. V. R. Dias and J. Wu, Euro. J. Inorg. Chem., 2008, 509–522, and
2008, 2113.
10 H. V. R. Dias and J. Wu, Angew. Chem., Int. Ed., 2007, 46, 7814–
7816.
11 H. V. R. Dias, R. G. Browning, S. A. Polach, H. V. K. Diyabalanage
and C. J. Lovely, J. Am. Chem. Soc., 2003, 125, 9270–9271.
12 P. Krishnamoorthy, R. G. Browning, S. Singh, R. Sivappa, C. J. Lovely
and H. V. R. Dias, Chem. Commun., 2007, 731–733.
13 K. Rangan, M. Fianchini, S. SIngh and H. V. R. Dias, Inorg. Chim.
Acta, DOI: 10.1016/j.ica.2008.1012.1028.
14 J. A. Flores and H. V. R. Dias, Inorg. Chem., 2008, 47, 4448–4450.
15 H. V. R. Dias, S. Singh and J. A. Flores, Inorg. Chem., 2006, 45, 8859–
8861.
16 H. V. R. Dias and S. Singh, Inorg. Chem., 2004, 43, 7396–7402.
17 H. V. R. Dias and S. Singh, Inorg. Chem., 2004, 43, 5786–5788.
18 L. Bourget-Merle, M. F. Lappert and J. R. Severn, Chem. Rev., 2002,
102, 3031–3066.
19 A. R. Siedle, R. J. Webb, F. E. Behr, R. A. Newmark, D. A. Weil, K.
Erickson, R. Naujok, M. Brostrom, M. Mueller, S.-H. Chou and V. G.
Young, Jr., Inorg. Chem., 2003, 42, 932–934.
20 A. R. Siedle, R. J. Webb, M. Brostrom, R. A. Newmark, F. E. Behr and
V. G. Young, Jr., Organometallics, 2004, 23, 2281–2286.
21 I. Haeger, R. Froehlich and E.-U. Wuerthwein, Eur. J. Inorg. Chem.,
2009, 2415–2428, and references therein.
N–H insertion in amines. Ethyl diazoacetate (0.057 g,
0.5 mmol) dissolved in CH2Cl2 (5 mL) was added by an automatic
syringe over a period of ~2 h to a stirred solution of the catalyst
(0.010 mmol, 2 mol%) and the amine (0.5 mmol of pyrrolidine
or aniline) in CH2Cl2 (9 mL). The resulting mixture was stirred
overnight at room temperature. C6Me6 (0.0275 mmol, 4.5 mg) was
added as the internal standard. The mixture was filtered through
a short plug of Celite, the solvent evaporated and the residue was
purified by flash chromatography on SiO2 (hexanes–ethyl acetate
(9 : 1)). The yields were estimated using 1H NMR spectroscopy by
integration of product resonances relative to the internal standard.
The NMR data of the products (ethyl N-pyrrolidinylacetate44
and ethyl 2-(phenylamino)acetate44) have been reported previously
(and are given in the ESI†).
22 M. N. Kopylovich, J. Lasri, M. F. C. Guedes da Silva and A. J. L.
Pombeiro, Dalton Trans., 2009, 3074–3084.
23 M. N. Kopylovich, K. V. Luzyanin, M. Haukka, A. J. L. Pombeiro and
V. Y. Kukushkin, Dalton Trans., 2008, 5220–5224.
24 M. Zhou, Y. Song, T. Gong, H. Tong, J. Guo, L. Weng and D. Liu,
Inorg. Chem., 2008, 47, 6692–6700.
25 P. V. Gushchin, M. R. Tyan, N. A. Bokach, M. D. Revenco, M. Haukka,
M.-J. Wang, C.-H. Lai, P.-T. Chou and V. Y. Kukushkin, Inorg. Chem.,
2008, 47, 11487–11500.
26 M. Zhou, P. Li, H. Tong, Y. Song, T. Gong, J. Guo, L. Weng and D.
Liu, Inorg. Chem., 2008, 47, 1886–1888.
27 E. A. Marihart, J.-B. Greving, R. Frohlich and E.-U. Wurthwein,
Eur. J. Org. Chem., 2007, 5071–5081.
28 N. Hesse, R. Froehlich, B. Wibbeling and E.-U. Wuerthwein, Eur. J. Org.
Chem., 2006, 3923–3937.
29 I. A. Guzei, K. R. Crozier, K. J. Nelson, J. C. Pinkert, N. J. Schoenfeldt,
K. E. Shepardson and R. W. McGaff, Inorg. Chim. Acta, 2006, 359,
1169–1176.
C–H insertion in ethers. Ethyl diazoacetate (0.057 g, 0.5 mmol)
dissolved in the ether (5 mL) was added by an automatic syringe
over a period of ~2 h to a stirred solution of the catalyst
(0.025 mmol, 5 mol%) in the ether (9 mL of diethyl ether or
tetrahydrofuran). The resulting mixture was stirred overnight
at room temperature, filtered through a short plug of Celite,
the solvent evaporated and the residue was purified by flash
chromatography on SiO2 (hexanes–ethyl ether (9 : 1)) yielding
the desired products as colourless oils. The yields were calculated
based on the weights of isolated and purified products, ethyl
3-ethoxybutanoate52 and ethyl (tetrahydrofuran-2-yl)acetate52 (see
ESI† for NMR data).
30 N. Hesse, R. Froehlich, I. Humelnicu and E.-U. Wuerthwein, Eur. J. In-
org. Chem., 2005, 2189–2197.
31 X. Dai and T. H. Warren, Chem. Commun., 2001, 1998–1999.
32 M. A. Cinellu, G. Minghetti, F. Cocco, S. Stoccoro, A. Zucca, M.
Manassero and M. Arca, Dalton Trans., 2006, 5703–5716.
33 C. Hahn, Chem.–Eur. J., 2004, 10, 5888–5899.
Acknowledgements
34 L. Cavallo, A. Macchioni, C. Zuccaccia, D. Zuccaccia, I. Orabona and
F. Ruffo, Organometallics, 2004, 23, 2137–2145.
35 J. A. Halfen, Curr. Org. Chem., 2005, 9, 657–669.
36 J. Perez, D. Morales, L. A. Garcia-Escudero, H. Martinez-Garcia, D.
Miguel and P. Bernad, Dalton Trans., 2009, 375–382.
37 L. D. Amisial, X. Dai, R. A. Kinney, A. Krishnaswamy and T. H.
Warren, Inorg. Chem., 2004, 43, 6537–6539.
We are grateful to The Welch Foundation (Y-1362 (C. J. L.) and
Y-1289 (H. V. R. D.)), and NSF (CHE-0314666, H. V. R. D.)
for funding our programs. The NSF provided partial funding
(CHE-9601771 and CHE-0234811) for the purchase of NMR
spectrometers used in the course of this work. We also wish to
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View Article Online
38 H. V. R. Dias, H.-L. Lu, H.-J. Kim, S. A. Polach, T. K. H. H. Goh, R. G.
Browning and C. J. Lovely, Organometallics, 2002, 21, 1466–1473, and
references therein.
39 M. P. Doyle, M. A. McKervey, and T. Ye, Modern Catalytic Methods
for Organic Synthesis with Diazo Compounds, Wiley, New York, 1998.
40 C. Jia, T. Kitamura and Y. Fujiwara, Acc. Chem. Res., 2001, 34, 633–
639.
41 D. J. Miller and C. J. Moody, Tetrahedron, 1995, 51, 10811–10843.
42 M. E. Morilla, M. J. Molina, M. M. Diaz-Requejo, T. R. Belderrain,
M. C. Nicasio, S. Trofimenko and P. J. Perez, Organometallics, 2003,
22, 2914–2918.
43 M. E. Morilla, M. M. Diaz-Requejo, R. Belderrain Tomas, M. C.
Nicasio, S. Trofimenko and P. J. Perez, Chem. Commun., 2002, 2998–
2999.
45 Y. Yamada, T. Yamamoto and M. Okawara, Chem. Lett., 1975, 361–
362.
46 S. Minakata, Y. Morino, Y. Oderaotoshi and M. Komatsu, Chem.
Commun., 2006, 3337–3339.
47 M. J. Zdilla and M. M. Abu-Omar, J. Am. Chem. Soc., 2006, 128,
16971–16979.
48 G. D. K. Kumar and S. Baskaran, Chem. Commun., 2004, 1026–
1027.
49 J. Han, Y. Li, S. Zhi, Y. Pan, C. Timmons and G. Li, Tetrahedron Lett.,
2006, 47, 7225–7228.
50 M. R. Fructos, T. R. Belderrain, P. de Fremont, N. M. Scott, S. P.
Nolan, M. M. Diaz-Requejo and P. J. Perez, Angew. Chem., Int. Ed.,
2005, 44, 5284–5288.
51 K. Khanbabaee, S. Basceken and U. Floerke, Eur. J. Org. Chem., 2007,
44 M. R. Fructos, T. R. Belderrain, M. C. Nicasio, S. P. Nolan, H. Kaur,
M. M. Diaz-Requejo and P. J. Perez, J. Am. Chem. Soc., 2004, 126,
10846–10847.
831–837.
52 A. Caballero, M. M. Diaz-Requejo, T. R. Belderrain, M. C. Nicasio, S.
Trofimenko and P. J. Perez, Organometallics, 2003, 22, 4145–4150.
7652 | Dalton Trans., 2009, 7648–7652
This journal is
The Royal Society of Chemistry 2009
©