Carbene Transfer and Carbene Insertion Reactions Catalyzed by a Mixed-Ligand Copper(I) Complex

Article abstract of DOI:10.1002/ejoc.201800863

The catalytic activity of the mixed-ligand copper(I) complex [Cu(PPh₃)₂(κ²-O,O"-lact)] (1) {lact = l-(+)-lactate} has been investigated in carbene transfer and carbene insertion reactions. Complex 1 catalytically promoted the diastereoselective cyclopropanation of olefins in the presence of ethyl diazoacetate (EDA), under mild conditions, and with a low catalyst loading (1 mol-%). In the case of internal alkenes, a trans/cis ratio of up to 93:7 was reached. Moreover, compound 1 easily promoted the insertion of the carbene fragment deriving from the decomposition of ethyl diazoacetate into O–H (alcohols and phenols) and N–H (amine) bonds, with formation of the corresponding ethyl 2-alkoxyacetate, ethyl 2-phenoxyacetate, and ethyl 2-aminoacetate derivatives in good to high yields.

Full text of DOI:10.1002/ejoc.201800863

A Journal of
Accepted Article
Title: Carbene Transfer and Carbene Insertion Reactions Catalyzed by
a Mixed Ligand Copper(I) Complex
Authors: Stefano Brenna and G. Attilio Ardizzoia
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201800863
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10.1002/ejoc.201800863
European Journal of Organic Chemistry
FULL PAPER
Carbene Transfer and Carbene Insertion Reactions Catalyzed by
a Mixed Ligand Copper(I) Complex
Stefano Brenna,*[a] and G. Attilio Ardizzoia[a]
Abstract: The catalytic activity of the mixed ligand copper(I)
complex [Cu(PPh3)2(κ2-O,O"-lact)] (1) (lact = l-(+)-lactate) has been
investigated in carbene transfer and carbene insertion reactions.
pyridine)[21] have been used with the aim of enhancing the
selectivity. Recently, chiral bicyclo bisoxazoline[22] and
tris(pyrazolyl)borate[23] copper(I) complexes showed remarkable
activity in the functionalization of O-H bonds. Despite being
usually less suitable for carbene insertion reactions, also
copper(I)-phosphine complexes have been successfully used in
the chemoselective insertion into N-H bonds[24-26] and in olefin
cyclopropanation.[27]
Complex
1
catalytically promoted the diastereoselective
cyclopropanation of olefins in the presence of ethyl diazoacetate
(EDA), in mild conditions and with a low catalyst loading (1% mol). In
the case of internal alkenes, a trans:cis ratio of up to 93:7 was
reached. Moreover, compound 1 easily promoted the insertion of the
carbene fragment deriving from ethyl diazoacetate decomposition
into O-H (alcohols and phenols) and N-H (amines) bonds, with the
formation of the corresponding ethyl 2-alkoxyacetate, ethyl 2-
phenoxyacetate and ethyl 2-aminoacetate derivatives in good to high
yields.
In the past, we also reported on ruthenium(II)[28] and copper(I)[29-
31]
complexes which demonstrated to be efficient catalysts in
olefin cyclopropanation when ethyl diazoacetate was used as
the carbenoid source. Continuing our search for copper catalysts
which promote carbene transfer to olefin and X-H bonds, herein
we investigated the catalytic activity of the mixed ligand
copper(I) complex [Cu(PPh3)2(κ2-O,O"-lact)] (1) (lact = L-(+)-
lactate) (Figure 1).[32] Compound 1 showed high trans-selectivity
in the EDA-assisted cyclopropanation of olefins (Figure 1) and a
good activity in the insertion of the carbenoid fragment into N-H
and O-H aliphatic and aromatic bonds (Figure 1).
Introduction
Transition metal-catalyzed transfer reactions of carbenes,
generated from diazo compounds, to unsaturated and saturated
substrates represent one of the most efficient tool for the
formation of new carbon-carbon or carbon-heteroatom bonds.[1-4]
The great interest in such reactions is related to the significance
and large range of applications of their products, which are often
useful synthetic intermediates for the construction of natural
products and biologically active molecules. For instance
cyclopropanes, obtained from the carbene transfer to differently
substituted olefin double bonds, are versatile intermediates that
can be converted into a variety of useful products by cleavage of
the strained three-membered ring.[5] Similarly, transition-metals
catalyzed insertion of carbenes into heteroatom-hydrogen bonds
(X-H) leads to α-amino esters, α-amino ketones and nitrogen-
containing heterocycles (X = N)[6] or α-alkoxy, α-aryloxy and α-
hydroxy esters, together with a variety of oxygen-containing
heterocyclic compounds (X = O).[7] These carbene transfer
reactions are promoted by several metals, for instance
rhodium,[8] iron,[6] ruthenium,[9] gold,[10] or copper.[11]
Focusing on copper based catalysts, large attention has been
dedicated to olefin cyclopropanation reactions, and both
experimental[12] and theoretical[13-15] studies have been
accomplished in order to elucidate the mechanism involved. A
variety of nitrogen based ligands, such as C2-symmetric
semicorrins,[16]
bis(oxazolines),[17]
bipyridines,[18]
polypyrazolylborates,[19] diiminophosphoranes[20] and tris(2-
Figure 1. Top: general reactions for carbene transfer to olefin and carbene
insertion into O-H and N-H bonds catalyzed by compound [Cu(PPh3)2(κ2-O,O"-
lact)], 1 (lact = L-(+)-lactate). Bottom: molecular structure of 1.
[a]
Prof. Dr. G. A. Ardizzoia, Dr. S. Brenna
Dipartimento di Scienza e Alta Tecnologia
Università degli Studi dell’Insubria and CIRCC
Via Valleggio 9, 22100 Como (Italy)
E-mail: stefano.brenna@uninsubria.it
https://www.uninsubria.it/hpp/stefano.brenna
Supporting information for this article is given via a link at the end of
the document.
1
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10.1002/ejoc.201800863
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FULL PAPER
Results and Discussion
Together with the desired products (A + B), diethyl maleate (C)
and diethyl fumarate (D), deriving from EDA self-coupling, were
always detected. In order to minimize the formation of these
side-products, an excess of olefin (Cu:EDA:olefin = 1:100:250
molar ratio) was employed. Moreover, EDA was added dropwise
to a CH2Cl2 solution of olefin and the catalyst, over a period of
12 h. As reported in Table 1, complex 1 showed to be a highly
active catalyst in the cyclopropanation of terminal olefins (entries
1-5), and activated internal ones (entry 6), in mild conditions. At
lower temperatures (0 °C) species 1 still showed a good activity
in the cyclopropanation of styrene (entry 2), although a lesser
yield was observed. On further lowering the temperature down
to -30°C, the activity of catalyst 1 dropped dramatically. Poor
yields were attained in the conversion of electron poor internal
olefins (entries 7-9); worthy of note, when diethyl maleate and
diethyl fumarate were used as substrates (entries 8-9), the
cyclopropanation products were detected only in traces. Yields
in cyclopropane products are in accord with those reported for
copper(I) catalysts with nitrogen-containing ligands[16-21, 29-31] and
to some extent higher than previously reported phosphine-
containing copper(I) species.[33]
In the conversion of styrene into the corresponding
cyclopropane esters, most of the copper(I) catalysts provided
the trans isomer as the main product,[34] the common trans:cis
ratio ranging from 50:50 to 75:25.[29-31] Also compound 1
confirmed this trend, providing a 70:30 trans:cis ratio in the
catalytic cyclopropanation of styrene, while a lower trans-
diastereoselectivity was observed using α-methylstyrene as
substrate (entry 4). Finally, complex 1 exhibited a remarkable
diastereoselectivity in the cyclopropanation of cyclohexene
(entry 6), where a 93:7 ratio was achieved.
Olefin cyclopropanation
Scheme 1. General olefin cyclopropanation reactions catalyzed by compound
[Cu(PPh3)2(κ2-O,O"-lact)], 1, leading to the formation of the desired
cyclopropane derivatives (A+B) and diethyl maleate (C) and diethyl fumarate
(D) as side-products.
Table 1. Olefin cyclopropanation by ethyl diazoacetate (EDA) decomposition
catalyzed by compound 1.a
Entry
1
Olefin
A+B (%)b
88 (79)
A:B ratioc
27:73
2d
3e
32
<5
26:74
-
4
86 (71)
42:58
Together with mono-alkenes, also dienes were employed as
substrates in the copper-catalyzed cyclopropanation reactions.
Indeed, 3-(1-isobutenyl)-2,2-dimethyl cyclopropanecarboxylic
acid (chrysanthemic acid) is a key intermediate of pyrethroid
insecticides[35] and the conversion of 2,5-dimethyl-2,4-hexadiene
(DMHD) into the corresponding chrysantemate esters by
diazoacetates decomposition represents a fundamental target in
industrial applicable processes.[36] Consistently with what
observed for mono-olefins, when complex 1 was used to
catalyze the conversion of conjugated di-olefins into the
corresponding cyclopropanes (entry 10), the trans isomer was
always the major product.
5
6
85
79
31:69
7:93f
7
<5
-
8
<5
<5
78
-
9
-
Insertion into O-H bonds
10
34:66
Once established the propensity of compound 1 to promote
carbene transfer to an olefin C=C bond, we investigated other
catalytic reactions where a carbenoid species is involved, i.e.
carbene insertions into E-H bonds (E = O, N). Indeed, the
accepted mechanism for such reactions considers the formation
of an electron-deficient metal-carbene and its subsequent
insertion into the N-H or O-H bond.[37] Being a metal-carbene
also the active species in olefin cyclopropanation, and
considering the abovementioned activity of complex
[Cu(PPh3)2(κ2-O,O"-lact)] in olefin cyclopropanation, we were
confident about using our complex also to promote E-H
insertions. Concerning O-H insertions, both aliphatic and
aromatic alcohols have been converted to the corresponding
ethyl 2-alkoxoacetate (E) and ethyl 2-phenoxyacetate (F)
(Scheme 2) by means of ethyl diazoacetate decomposition.
Following the previous experiments on olefin cyclopropanation,
a Reactions conditions: 1/EDA/olefin =1/100/250; CH2Cl2 (8 mL), 20°C. b Yields
were determined by GC-MS analysis (internal standard: hexamethylbenzene)
of the bulk: (A + B) + (C + D) = 100%, after complete EDA consumption
(>99% in all runs) monitored by disappearance of νN
in infrared
N
≡
c
spectroscopy. Isolated yields in parenthesis for selected examples.
d
e
Determined by GC-MS analysis of the bulk. Performed at 0°C. Reaction
performed at -30°C. f In this specific case, the diastereoselectivity is referred to
exo:endo ratio.
According to Scheme 1, when complex 1 was dissolved in
dichloromethane under inert atmosphere in the presence of
olefins, the addition of ethyl diazoacetate (EDA) led to the
conversion of the substrate into the corresponding cyclopropane
derivatives with high yields (Table 1).
2
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10.1002/ejoc.201800863
European Journal of Organic Chemistry
FULL PAPER
only 1% mol catalyst with respect to the substrate was added,
and the diazo compound was yet again dropped over a 12-h
period to suppress the formation of undesired diethyl maleate
(C) and fumarate (D) (Scheme 2).
8
9
89
85
In the case of aliphatic substrates (Table 2) very high yields,
comparable to those obtained with other copper(I)
compounds,[38] were always obtained in the carbene insertion
into O-H bonds of primary alcohols (entries 1-5) regardless the
length of the alkylic chain. The insertion of the -CHCOOEt
fragment from ethyl diazoacetate proceeded with high yields for
secondary alcohols as well (entries 6-9). In some way unusual is
the situation when groups other than carbon-based ones are
attached to the side chain of the alcohol (entries 10-13): the
presence of Br atoms or NMe2 or CF3 substituents considerably
lowered the yield of conversion of the alcohol into the
corresponding ethyl 2-alkoxoacetate E. Further studies are
ongoing to clarify this point.
10
11
12
13
58
44
<5
<5
<5
COOEt
H
EtOOC
N2
, 1% mol
1
R
R
H
OEt
+
+
O
O
H
COOEt
CH2Cl2, 20°C
-N2
O
14c
E
C/D
a
b
Reactions conditions: 1/EDA/alcohol =1/100/250; CH2Cl2 (8 mL), 20 °C.
N2
EtOOC
R'
Yields were determined by GC-MS analysis (internal standard:
hexamethylbenzene) of the bulk: E + (C + D) = 100%, after complete EDA
R'
, 1% mol
1
COOEt
OEt
+
+
H
COOEt
H
CH2Cl2, 20°C
-N2
consumption (>99% in all runs) monitored by disappearance of νN N in infrared
O
O
H
O
≡
c
spectroscopy. Isolated yields in parenthesis for selected examples.
C/D
F
Determined by GC-MS analysis of the bulk. c Reaction performed at -30°C.
Scheme 2. General O-H insertion reactions catalyzed by compound 1,
leading to the formation of the desired ethyl 2-alkoxoacetate (E) and ethyl 2-
phenoxyacetate (F) derivatives and diethyl maleate (C) and diethyl fumarate
(D) as side-products.
Then, compound [Cu(PPh3)2(κ2-O,O"-lact)], 1, was also tested
as catalyst in the carbene insertion into O-H bonds of phenols
(Scheme 3, Table 3). The yields of conversion of phenols into
the corresponding O-H functionalized products F are in accord
with those observed for previous copper(I)-phosphine
catalysts.[22,39] Worthy of note, besides the expected ethyl 2-
phenoxyacetate (F), also the product coming from insertion into
the aromatic C-H bond (G) was detected. This is an unusual
behavior for a copper catalyst, as typically copper, palladium,
iron or rhodium active compounds are chemo-selective towards
the O-H insertion.[40] Differently, Zhang[40-41] and Shi[42]
demonstrated that the C-H functionalization takes place when
gold(I) species are used in combination with α-diazoesters. By
means of DFT calculations[40] they showed that the insertion into
the aromatic C-H bond is siteselective, occurring at the para-
position with respect to the OH group. However in our case,
catalyst 1 did not show a similar site-selectivity, as 1H NMR
inspection of the bulk provided evidence of the formation of a
mixture of regioisomers in all catalytic runs. A further combined
experimental and theoretical investigation will hopefully clarify
the exact nature of the C-H functionalized products.
Table 2. Carbene insertion into O-H bonds by means of ethyl diazoacetate
(EDA) decomposition catalyzed by compound 1.a
Entry
Alcohol
Product E
Yield (%)b
84
1
2
3
77
76
4
86
5
6
93 (85)
78
Scheme 3. Insertion of carbene into O-H bonds of phenols catalyzed by
compound 1, leading to ethyl 2-phenoxyacetate (F), the products of C-H
insertion (G) and diethyl maleate (C) and diethyl fumarate (D).
7
77
3
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10.1002/ejoc.201800863
European Journal of Organic Chemistry
FULL PAPER
reported catalysts[43] and with respect to the analogous
insertions into O-H bonds (yields ≥ 76%, Table 2) catalyzed by 1.
The insertion of the -CHCOOEt fragment proceeded with
secondary amines as well (entries 6-8), yields being only slightly
poorer with aliphatic amines (entries 7-8). Unfortunately, a
preliminary screening on the activity of complex 1 towards the
carbene insertion into N-H bonds of anilines resulted
unsuccessful, with yields being always lower than 10% when
aniline and N-ethyl aniline were used as test substrate. Hence,
this reaction was not further investigated.
Table 3. Carbene insertion into O-H bonds of phenols by means of ethyl
diazoacetate (EDA) decomposition catalyzed by compound 1.
Entry
1
Phenol
F
G
F(%)b
G(%)b
55
17
2
3
4
63
50
38
29
19
13
42
Table 4. Carbene insertion into N-H bonds of amines by means of ethyl
diazoacetate (EDA) decomposition catalyzed by compound 1.
Entry
1
Amine
Product H
Yield (%)b
60 (48)
2
3
65
55
5
53
a
b
Reactions conditions: 1/EDA/phenol =1/100/250; CH2Cl2 (8 mL), 20°C.
Yields were determined by GC-MS analysis (internal standard:
hexamethylbenzene) of the bulk: (F + G) + (C + D) = 100%, after complete
EDA consumption (>99% in all runs) monitored by disappearance of νN in
infrared spectroscopy.
N
≡
4
54
50
The lower yield obtained with 2,6-dimethyl phenol (entry 6) is
probably imputable to the higher steric hindrance imposed by
the ortho-methyl groups in the resulting product F; worthy of
note, in this case the percentage of the C-H functionalized
phenol is also the highest among the series.
5
6
58
Insertion into N-H bonds
7
8
48
42
a
b
Reactions conditions: 1/EDA/amine =1/100/250; CH2Cl2 (8 mL), 20°C.
Yields were determined by GC-MS analysis (internal standard:
hexamethylbenzene) of the bulk: H + (C + D) = 100%, after complete EDA
Scheme 4. Insertion of carbene into N-H bonds of aliphatic amines catalyzed
by compound 1, leading to product H, diethyl maleate (C) and diethyl fumarate
(D).
consumption (>99% in all runs) monitored by disappearance of νN N in infrared
spectroscopy. Isolated yields in parenthesis for selected examples.
≡
.
Complex [Cu(PPh3)2(κ2-O,O"-lact)] proved to be active also in
the functionalization of N-H bonds of aliphatic and benzylic
amines by means of ethyl diazoacetate decomposition (Scheme
4, Table 4), leading to ethyl 2-aminoacetate derivatives (H). Yet
again, only 1% mol catalyst was added, and the diazo
compound was dropped over a 12-h period to suppress the
formation of undesired diethyl maleate (C) and fumarate (D)
(Scheme 4).
Asymmetric reactions
The presence of a chiral anion such as L-(+)-lactate in complex
[Cu(PPh3)2(κ2-O,O"-lact)] prompted us to inspect its potential use
in asymmetric carbene transfer and insertion reactions (Scheme
5).
As reported in Table 4, primary amines (entries 1-5) could be
easily converted into products H in good yields (≥ 50%), despite
overall a lower activity was observed compared to previously
4
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10.1002/ejoc.201800863
European Journal of Organic Chemistry
FULL PAPER
Scheme 5. a) Asymmetric cyclopropanation of styrene promoted by complex 1 via ethyl diazoacetate decomposition. b) Asymmetric insertion of the carbene
generated by decomposition of Methyl diazophenylacetate (MPDA) into the O-H bond of benzyl alcohol.
Styrene was first used as reference substrate to evaluate the
asymmetric induction in olefin cyclopropanation. The catalytic
run was performed following the conditions described above
(Table 1), other than the bulk mixture obtained after complete
together with the desired ethyl 2-phenoxyacetate, the formation
of products deriving from C-H functionalization was also
observed, in a process which is quite unusual for copper(I)
catalysts.
EDA consumption
was
analyzed using chiral gas
chromatography (see Experimental). Unfortunately, compound 1
did not induce any enantiomeric excess in the cyclopropanation
of styrene, as demonstrated by the resulting chromatogram
(Figure S1). A similar behavior was observed in the carbene
insertion into benzyl alcohol O-H by decomposition of methyl
diazophenylacetate MPDA[44] (Scheme 5b). In this case, the
enantiomeric excess was quantified via 1H NMR analysis, by
Experimental Section
All reactions were carried out under purified nitrogen using standard
Schlenk techniques. Solvents were dried and distilled according to
standard procedures prior to use. NMR spectra were recorded with an
AVANCE 400 Bruker spectrometer at 400 MHz for 1H NMR and 162 MHz
for 31P{1H} NMR. Chemical shifts are given as δ values in ppm relative to
residual solvent peaks as the internal reference (for 1H NMR) and to
external H3PO4 (85%) (for 31P NMR). J values are given in Hz. Infrared
Spectra were acquired on a Shimadzu Prestige-21 spectrophotometer
with a 1cm-1 resolution. Quantitative analyses of products in the catalytic
runs were performed on a Finnigan Trace GC with a DB-5MS UI capillary
gradual
addition
of
europium
tris[3-
(heptafluoropropylhydroxymethylene)-(+)-camphorate] (Eu(hfc)3)
to a CDCl3 solution of the bulk. Once again, a nearly 50:50
distribution was obtained for the two enantiomers (Figures S2-
S3). The lack of enantioselectivity shown by complex
[Cu(PPh3)2(κ2-O,O"-lact)] could probably be attributed to the
column (30 m, 0.25 mm) equipped with
a Finnigan Trace Mass
Spectrometer. Enantioselectivities in styrene cyclopropanation were
analyzed on Shimadzu GC-17A gas chromatograph equipped with a
chiral PS225 capillary column (25 m, 0.25 mm). [Cu(PPh3)2(κ2-O,O"-lact)]
(1) was prepared as previously reported[32] and its purity was assessed
by elemental analysis, 1H and 31P NMR (Supporting Information); methyl
diazophenylacetate (MDPA) was prepared following literature
methods.[44] All other chemicals were of reagent grade quality, were
purchased commercially (Aldrich, Acros, TCI Chemicals) and used as
received.
fluxionality shown by the lactate anion in dichloromethane
[32]
solution, at room temperature.
This fluxionality is minimized
on lowering the temperature to -30°C,[32] but regrettably when
both the cyclopropanation of styrene and the reaction between
benzyl alcohol and MPDA were performed at -30°C, the
products of the two catalytic runs could only be detected in
traces (Table 1, entry 3 and Table 2, entry 14).
General procedure for olefin cyclopropanation
Conclusions
In a standard experiment, to a solution of complex 1 (10 mg, 0.015 mmol)
and olefin (3.75 mmol) in dichloromethane (8 ml) at room temperature
and under inert atmosphere, ethyl diazoacetate (EDA) (160 μL, 1.50
mmol) was added dropwise over a period of 12 h (Cu:EDA:olefin molar
ratio 1:100:250). The consumption of EDA was monitored by infrared
The catalytic activity in carbene transfer and insertion reactions
of the mixed ligand copper(I) complex [Cu(PPh3)2(κ2-O,O"-lact)]
(1) has been reported. Complex
1
promoted olefin
cyclopropanation by ethyl diazoacetate decomposition under
very mild conditions and a very low catalyst loading (1% mol).
Especially in the case of internal olefins, compound 1 showed
remarkably high selectivity towards the formation of the trans
isomer. Additionally, [Cu(PPh3)2(κ2-O,O"-lact)] (1) promoted
carbene insertion into O-H and N-H bonds as well. In particular,
in the case of carbene insertion into O-H bonds of phenols,
spectroscopy (νN N, 2109 cm-1). After complete conversion of EDA,
≡
yields and diastereoselectivity (trans:cis ratio) were determined by GC-
MS analysis of the crude. In selected cases, products were isolated after
removal
of
the
solvent
and
column
chromatography
(dichloromethane:hexane = 6:4). Their collected analytical data were in
agreement to those reported in the literature.[29]
5
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10.1002/ejoc.201800863
European Journal of Organic Chemistry
FULL PAPER
General procedure for carbene insertion into O-H bonds
[6]
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In a standard experiment, to a solution of complex 1 (10 mg, 0.015 mmol)
and alcohol or phenol (3.75 mmol) in dichloromethane (8 ml) at room
temperature and under inert atmosphere, ethyl diazoacetate (EDA) (160
[7]
[8]
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a period of 12 h
(Cu:EDA:alcohol molar ratio 1:100:250). The consumption of EDA was
monitored by infrared spectroscopy (νN≡N, 2109 cm-1). After complete
conversion of EDA, the distribution of products was determined by GC-
MS analysis of the bulk using hexamethylbenzene as internal standard.
In selected cases, products were isolated after removal of the solvent
and column chromatography (hexane:diethylether = 20:1). Their collected
analytical data were in agreement to those reported in the literature.
O. I. van den Boomen, R. G. E. Coumans, N. Akeroyd, T. P. J. Peters,
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Norrby, Chem. Eur. J. 2002, 8, 177-184.
In a standard experiment, to a solution of complex 1 (10 mg, 0.015 mmol)
and the amine (3.75 mmol) in dichloromethane (8 ml) at room
temperature and under inert atmosphere, ethyl diazoacetate (EDA) (160
[13] Q. Meng, M. Li, J. Mol. Struct.: THEOCHEM 2006, 765, 13-20.
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THEOCHEM 2004, 711, 193-199.
μL, 1.50 mmol) was added dropwise over
a period of 12 h
(Cu:EDA:amine molar ratio 1:100:250). The consumption of EDA was
monitored by infrared spectroscopy (νN≡N, 2109 cm-1). After complete
conversion of EDA, yield was determined by GC-MS analysis of the bulk
using hexamethylbenzene as internal standard. In selected cases,
products were isolated after removal of the solvent and column
chromatography (hexane:diethylether = 20:1). Their collected analytical
data were in agreement to those reported in the literature.
[16] H. Fritschi, U. Leutenegger, A. Pfaltz, Helv. Chim. Acta 1988, 71, 1553-
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This work was partially supported by the Ministero dell’Università
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6
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10.1002/ejoc.201800863
European Journal of Organic Chemistry
FULL PAPER
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7
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201800863
European Journal of Organic Chemistry
FULL PAPER
Keywords: carbene transfer; homogeneous catalysis; cyclopropanation; carbene insertion; copper
8
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10.1002/ejoc.201800863
European Journal of Organic Chemistry
FULL PAPER
Entry for the Table of Contents
Key Topic: Carbene Transfer
FULL PAPER
An easily-prepared and low-cost
copper(I) homogeneous catalyst has
been investigated in carbene transfer
reactions. High yields and selectivities
were achieved in olefin
Stefano Brenna,* G. Attilio Ardizzoia
Page No. – Page No.
Carbene Transfer and Carbene
Insertion Reactions Catalyzed by a
Mixed Ligand Copper(I) Complex
cyclopropanation and O-H and N-H
insertions.
9
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