An effective dual copper-and sulfide-catalytic system for the epoxidation of aldehydes with phenyldiazomethane

Article abstract of DOI:10.1002/adsc.201300606

Epoxides have been obtained from alde-hydes and phenyldiazomethane using catalytic amounts of both the copper homoscorpionate com-plexes Tp ^xCuL (Tp^x = homoscorpionate ligand; L = acetonitrile or tetrahydrofuran, THF) and dimethyl sulfide (SMe₂) in high yields and diasteroselectivities, and with activities higher (TOF = 46 h^-1) than those already known with rhodium-or copper-based cata-lysts. Among the copper(I) homoscorpionate com-plexes tested, Tp^Br3Cu(NCCH ₃) showed the highest catalytic activity under mild conditions. The catalytic activity is controlled by electronic effects induced by the Tp ^x ligand as well as by the stability of the Tp^xCu(SR ₂) adducts. Indeed, in the case of Tp^Ms as ligand, the Tp^MsCu(THT) (THT = tetrahydrothio-phene) and Tp ^MsCu(SMe₂) species could be isolated as very stable crystalline solids, the molecular struc-ture of the former being confirmed by single-crystal X-ray diffraction analysis. The in situ generation of PhCHN ₂ from benzaldehyde tosylhydrazone sodium salt at 60 °C in methyl tert-butyl ether as solvent and Tp^MsCu(THF) as the catalyst also showed high cata-lytic activities, improving those already reported with copper-based catalysts.

Full text of DOI:10.1002/adsc.201300606

FULL PAPERS
DOI: 10.1002/adsc.201300606
An Effective Dual Copper- and Sulfide-Catalytic System for the
Epoxidation of Aldehydes with Phenyldiazomethane
Ana Pereira,a Carmen Martꢀn,a Celia Maya,b Tomꢁs R. Belderrain,a,*
and Pedro J. Pꢂreza,*
a
Laboratorio de Catꢁlisis Homogꢂnea, Unidad Asociada al CSIC, CIQSO-Centro de Investigaciꢃn en Quꢀmica Sostenible
and Departamento de Quꢀmica y Ciencia de los Materiales, Campus de El Carmen s/n, Universidad de Huelva, 21007
Huelva, Spain
Fax : (+34)-95-921-9942; e-mail: trodri@dqcm.uhu.es or perez@dqcm.uhu.es
Departamento de Quꢀmica Inorgꢁnica-Instituto de Investigaciones Quꢀmicas, Universidad de Sevilla-Consejo Superior de
b
Investigaciones Cientꢀficas, Avda. Amꢂrico Vespucio 49, Isla de la Cartuja, 41092 Sevilla, Spain
Received: July 8, 2013; Published online: September 9, 2013
This work is dedicated to Prof. Antonio Laguna on the occasion of his 65th birthday.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201300606.
Abstract: Epoxides have been obtained from alde- ligand, the TpMsCu
ACHTUNGTNER(NUNG THT) (THT=tetrahydrothio-
hydes and phenyldiazomethane using catalytic phene) and TpMsCu
AHCTUNGTRENNUNG
amounts of both the copper homoscorpionate com- as very stable crystalline solids, the molecular struc-
plexes TpxCuL (Tpx =homoscorpionate ligand; L= ture of the former being confirmed by single-crystal
acetonitrile or tetrahydrofuran, THF) and dimethyl X-ray diffraction analysis. The in situ generation of
sulfide (SMe2) in high yields and diasteroselectivities, PhCHN2 from benzaldehyde tosylhydrazone sodium
and with activities higher (TOF=46 hÀ1) than those salt at 608C in methyl tert-butyl ether as solvent and
already known with rhodium- or copper-based cata- TpMsCu
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
catalytic activity under mild conditions. The catalytic
activity is controlled by electronic effects induced by
the Tpx ligand as well as by the stability of the Keywords: copper; diazo compounds; epoxidation;
ACHTUNGTRENNUNG
TpxCu(SR2) adducts. Indeed, in the case of TpMs as homogeneous catalysis; sulfide ylides
Introduction
groups may not be compatible with those basic condi-
tions required.[9] To overcome this limitation, Aggar-
Epoxides are broadly used as intermediates in organic
synthesis[1] and are part of many biologically active
compounds.[2] A variety of methods has been devel-
oped for the preparation of epoxides as cyclization of
halohydrins [Eq. (1)],[3] the Darzens condensation of
a-halo esters [Eq. (2)],[4] the alkene oxidation [Eq.
(3)][5] and sulfide ylide addition to aldehydes or ke-
tones [Eq. (4)].[6,7,8] Among them, the latter has
drawn much attention during the past two decades
since it finds applications from enantioselective,[6] cat-
alytic[7] and practical points of view.[8]
The major drawback of the reactions between sul-
fonium salts and carbonyl compounds is that these
processes are usually mediated by a base. Therefore,
carbonyl compounds containing sensitive functional
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An Effective Dual Copper- and Sulfide-Catalytic System for the Epoxidation of Aldehydes
Table 1. Homoscorpionate ligands employed in this work.
TpxCu R1 R2 R3
(NCMe)
TpBr3Cu
(NCMe), 1 Br Br Br
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
TpPhCu
(NCMe), 2
TpMe2Cu, 3
TpMsCu
(THF), 4
G
H
Me
H
H
H
H
Ph
Me
Ms
AHCTUNGTRENNUNG
that not only surpasses that of any previous copper-
based system but also compares well with those of al-
ready reported rhodium-based catalysts.
Scheme 1. The strategy of catalytic epoxidation of aldehydes
with diazo compounds, catalyzed by the combination of
metal complexes and sulfides.
Results and Discussion
Catalytic Activities of TpxCu(I) Complexes in the
Epoxidation of Aldehydes with Phenyldiazomethane
wal and co-workers[7a] developed an epoxidation reac- via Sulfur Ylides
tion, under neutral conditions, which consisted of the
reaction of a ketone or an aldehyde with in situ gener- With the aim of comparing the catalytic activities of
ated sulfur ylides, the latter being formed from the TpxCu complexes with those tested by Aggarwal and
transition metal-catalyzed decomposition of a diazo co-workers, we have employed them as catalyst pre-
compound in the presence of catalytic amounts of cursors in the probe reaction of benzaldehyde and
such a sulfide (Scheme 1). The neutral conditions, phenyldiazomethane, in the presence of catalytic
therefore, made these transformations valid to be em- amounts of dimethyl sulfide as well. A solution of
ployed with enolizable and base-sensitive aldehydes PhCHN2 in toluene (5 mL, 0.1M) was slowly added
and ketones.
over 1 h to a solution of benzaldehyde (0.5 mmol), di-
In addition, Aggarwal et al.[10] have described methyl sulfide (0.05 mmol) and the corresponding
a methodology which involves the in situ generation TpxCuL complex (0.005 mmol) in CH2Cl2 [Eq. (5)].
of the diazo compound from the corresponding tosyl-
hydrazone salt in the presence of a phase-transfer cat-
alyst (PTC). In spite of the use of copper salts in their
initial investigations,[7d] only rhodium acetate was
used under the new conditions, since it was found to
be more efficient than copper acetylacetonates.[10]
In the past decade, we have developed the use of
TpxCuL (Tpx =trispyrazolylborate ligand;[11] L=ace-
tonitrile or THF) complexes as catalysts for several The reaction mixture was additionally stirred at room
carbene – from diazo compounds – transfer reactions, temperature for 1 h. The results of this series of ex-
such as additions to olefins or alkynes[12] as well as in- periments are summarized in Table 2.
[13]
O,[14] N,[15] or
The complex TpBr3Cu
ACTHNGUTRENU(NG NCCH3) (5 mol% relative to
À
sertions into X H bonds (X=C,
Si[16]). These scorpionate ligands modulate the elec- aldehyde) along with 10% of Me2S (relative to alde-
tronic and steric properties of the metal center, allow- hyde) led to the best results, a 85% yield of epoxide
ing the appropriate tuning of the catalytic activity of being obtained under the aforementioned conditions
the corresponding TpxM complex. With those prece- (blank experiments carried out without sulfide provid-
dents, we decided to explore the catalytic potential of ed sitlbenes whereas in the absence of copper no
several TpxCuL complexes toward the reaction of al- diazo consumption was observed after a week). More-
dehydes with in situ generated sulfur ylides from the over, the yield was improved by reducing the volume
decomposition of phenyldiazomethane. Herein, we of dichloromethane to 1 mL (92% yield, entry 2).
report the results obtained with a series of TpxCu cat- These results are better than those reported for
alysts (Table 1), from which the complex TpBr3Cu- Rh
ACHTUNGTRENNUNG(NCMe) (1) has emerged with a remarkable activity required a 20% loading of Me2S and 24 h of slow ad-
2ACHTUNGTRENN(UNG OAc)4 as catalyst (76% yield, entry 6), that also
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Ana Pereira et al.
FULL PAPERS
Table 2. Aldehyde epoxidation with phenyldiazomethane
tive to aldehyde). Remarkably, the turnover frequen-
cy (TOF) displayed by complex 1 was established as
46 hÀ1, significantly higher that those previously re-
ported with the above rhodium- (3.2 hÀ1) or copper-
based (5.4 hÀ1) systems. In contrast with the excellent
activity of complex 1, moderate (2) to low (3 and 4)
yields were obtained with the other Tpx-containing
complexes. It is worth mentioning that the extremely
using TpxCuL and Me2S as catalysts.
Entry
Catalyst
Yield [%]
trans:cis
1
2
3
4
5
6
7
TpBr3Cu
TpBr3Cu
ACHTUNGTRENNUNG
G
85
92
57
19
5
96:4
96:4
97:3
95:5
98:2
88:12
90:10
TpPhCu
ACHTUNGTRENNUNG
TpMe2Cu, 3[a]
TpMsCu(NCMe), 4[a]
Rh2A(OAc)4
Cu(acac)2
ACHTUNGTRENNUNG
low catalytic activity observed with TpMsCu
ACTHNUTRGNEU(GN THF) is
[c]
[d]
G
76
97
at variance with the fact that this complex is a very
active catalyst in olefin cyclopropanation using EDA
(ethyl diazoacetate), for which TOF values of 250 hÀ1
were found.[12a,b] This apparent contradiction will be
discussed later.
As shown in Table 2, this procedure provided the
trans isomer as the major component in the mixture
of epoxides, assessing a highly diastereoselective
transformation in which the ratio of isomers seems to
be non-catalyst dependent. This is in agreement with
an already reported proposal that the high trans selec-
ACHTUNGTRENNUNG
[a]
Ratio [TpxCuL]:
ACTHUNGTRENNUG[Me2S]:ACHTUNGTERN[NUGN PhCHN2]: [benzaldehyde] of
1:10:100:100. 5 mL of CH2Cl2 were used. The conversions
were determined by 1H NMR spectroscopy. Percentage
1
of epoxide was determined by H NMR at the end of the
reaction using furan as internal standard (trans and cis
stilbene accounted for initial 100% of phenyldiazome-
thane).
1 mL of CH2Cl2 was used.
A solution of phenyldiazomethane (1.5 mmol in 6 mL
[b]
[c]
t-BuOMe) was added over 24 h to a solution of the
aldehyde (1 mmol), dimethyl sulfide (0.2 mmol) and tivity observed in the case benzyl-stabilized ylides
Rh
[cat]:
ref.[7d]).
G
(0.01 mmol)
in
4 mL
(ratio
with aromatic aldehydes is the result of the non-rever-
sible formation of the anti-betaine, which affords the
trans stilbene epoxide by rotation and ring clo-
A
G
[d]
A solution of phenyldiazomethane (1.5 mmol in 6 mL
CH2Cl2) was added over 3 h to a solution of aldehyde
(1 mmol), dimethyl sulfide (1.0 mmol) and CuACTHUNRGTNEUNG(acac)2
(0.1 mmol) in CH2Cl2 (4 mL) and the reaction mixture
was stirred at room temperature for 18 h (ratio
AHCTUNGTRENNUNG
sure.[7o,17]
Once we had determined that TpBr3Cu
ACTHNUTRGNEN(UG NCCH3)
was the most active catalyst, we were interested in an-
alyzing the influence in the reaction outcome of the
sulfide loading used. Consequently, we carried out the
epoxidation reactions of several aldehyde substrates
using variable amounts of dimethyl sulfide (3 or
10 mol%). As shown in Table 3, the series of alde-
A
ACHTUNGTRENNUNG[Me2S]:ACHTUNGTRENNUNG[PhCHN2]:[benzaldehyde] of 1:100:150:100,
dition.[7d] On the other hand, although high yields of hydes employed was efficiently converted into the
epoxide (97%, entry 7) were reported by Aggarwal corresponding epoxides even at a 3% sulfide loading
and co-workers using Cu
(acac)2,[7d] in this case the sul- in 1 h. This efficiency improves that of the previously
ACHTUNGTRENNUNG
fide was employed in a stoichiometric manner (rela- Rh2ACHNUTTGRENNUNG
(AcO)4-based system[7d] that required 20% of sul-
Table 3. Aldehyde and ketone epoxidation with phenyldiazonethane using 1 as the catalyst precursor.
Entry
Aldehyde
Dimethyl sulfide (mol%)
Product
Yield [%][b]
trans:cis[b]
1
2
3
4
5
6
7
8
benzaldehyde
benzaldehyde
3
10
3
10
3
10
3
10
3
10
100
100
5
5
6
6
7
7
8
8
9
9
10
11
85
96:4
97:3
97:3
92:8
96:4
97:3
70:30
75:25
85:15
89:11
–
>99 (95[c])
p-nitrobenzaldehyde
p-nitrobenzaldehyde
p-chlorobenzaldehyde
p-chlorobenzaldehyde
cyclohexanecarboxaldehyde
cyclohexanecarboxaldehyde
valeraldehyde
valeraldehyde
cyclohexanone
acetophenone
>99
92
85
97
77
70
78
77
31
8
9
10
11
12
–
[a]
[catalyst]:
added over 1 h at room temperature to a solution of aldehyde (0.5 mmol), dimethyl sulfide (3 or 10 mol%) and
TpBr3Cu
(NCMe) (0.005 mmol) in CH2Cl2 (1 mL).
Yields and cis:trans ratios were determined by H NMR spectroscopy using furan as internal standard.
Isolated yield of products.
ACHTUNGTRENNUNG[sulfide]:ACHTUNRTEGG[NNUN aldehyde]:CAHTNUGTREN[NUGN diazo]=1:X:100:100. A solution of phenyldiazomethane (0.5 mmol in 5 mL toluene) was
ACHTUNGTRENNUNG
[b]
[c]
1
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An Effective Dual Copper- and Sulfide-Catalytic System for the Epoxidation of Aldehydes
fide loading and 24 h to complete the diazo consump-
tion.
Mean while we have also tested the activity of
TpBr3Cu
ACHTUNGTRENNUNG(NCCH3) with ketones as substrates, particu-
larly cyclohexanone and acetophenone. Unfortunate-
ly, the slow addition (12 h) of a solution of PhCHN2
in toluene onto a solution of the corresponding
ketone in CH2Cl2 in the presence of 1 (10 mol%) and
a stoichiometric amount of THT (THT=tetrahydro-
thiophene) afforded the corresponding epoxides 10
and 11, in low yields (31% and 8%, respectively).[7d,18]
Figure 1. Steric interactions between the R3 groups of the
Tpx ligand and 3-hexyne (left) and sulfide (right) during the
carbene transfer steps.
nation reactions using EDA,[19] we have demonstrated
the control of the alkyne structures in the chemose-
lectivity of the process. For instance, in the sterically
Effect of the Catalyst and the Sulfide Structures
We have also studied the effect of the nature of the hindered TpMsCu core, cyclopropenation of 3-hexyne
sulfide by using a series of this co-catalyst in the is disfavoured compared with the dimerization of the
probe reaction of benzaldehyde and phenyldiazome- diazo compound to give diethyl fumarate or maleate.
thane, with 1 as the catalyst. From the experimental This behaviour was attributed to steric repulsions be-
data (Table 4) it seems clear that the increasing steric tween the R3 groups of the Tpx ligand and 3-hexyne,
hindrance of the sulfide resulted in decreasing yields which would prevent the approach of the alkyne to
of epoxide, in accord with the previous observations the carbene ligand (Figure 1, left). From the data
by Aggarwal and co-workers with Rh2ACTHNUTRGNEUNG
(AcO)4.[7d] In shown in Table 4, it seems reasonable to propose that
our case, steric factors are somewhat more significant the approach of a bulky sulfide to the copper carbene
as inferred from the lower yield of the stilbene oxide (Figure 1, right) is controlling the reaction outcome,
obtained for the isopropyl sulfide.
the less sterically hindered dimethyl sulfide being the
The coordination of trispyrazolylborate ligands to most appropriate sulfide to promote high yields into
metal centers displays a common feature in most epoxides.
cases: the ancillary ligand occupies a significantly
Scheme 2 shows a mechanistic picture of the overall
high volume around that center, due to the typical transformation. Dissociation of the nitrile ligand from
values of the cone angles of the Tpx ligands.[11] As the catalyst precursor is well established[20] as the first
a result of that, the catalytic pocket in these TpxCu step to render a coordinative and electronically unsa-
compounds is influenced by the bulkiness of the sub- turated species of composition TpxCu that could fur-
stituents at the pyrazolyl ring. Thus, in a recent contri- ther react with phenyldiazomethane. The resulting
bution from this laboratory about alkyne cycloprope- copper-carbene intermediate may undergo two differ-
ent reactions, either with a second molecule of the
diazo reagent or with the organic sulfide, the latter
leading to the release of the sulphur ylide and the cat-
alytic species TpxCu. The epoxide is formed in a non
metal-mediated step from that ylide and the aldehyde.
Actually, the prequilibrium that delivers such TpxCu
species could also take place with the SR2 cocatalyst,
exerting the control of the amount of the real catalyt-
ic species in solution.
Table 4. Yield of epoxide from benzaldehyde with
TpBr3Cu
(NCMe) as catalyst in the presence of catalytic
amounts of sulfide.
ACHTUNGTRENNUNG
Entry
Sulfide
Yield [%]
trans:cis
96:4
1
2
92
97
As already mentioned, TpMsCu
ACHTNUTRGNEUNG(THF) showed low
97:3
catalytic activities in the epoxidation reactions, in con-
trast with its catalytic capabilities toward the cyclo-
propanation of styrene using EDA in quantitative
yields and with high reaction rates (250 hÀ1).[12] The
lack of reactivity described herein is in agreement
with the previous observation that EDA was not con-
sumed after 24 h, in the reaction with allyl ethyl ether
and this catalyst.[21] Such an anomalous behaviour was
then attributed to the formation of a very stable
copper-olefin complex, precluding olefin decoordina-
tion and therefore blocking diazo compound coordi-
nation and further metallocarbene formation. In
3
16
46
95:5
6
85:15
[a]
Ratio
[TpxCu
ACHTUNTGREG(NUNN NCMe)]:ACHTUNRTGEN[GNNU sulfide]:ACHTUNGTREN[NUGN PhCHN2]:[benzalde-
hyde] 1:10:100:100. 1 mL of CH2Cl2 was used. The con-
versions were determined by H NMR spectroscopy. Per-
centage of epoxide at the end of the reaction using furan
as internal standard (trans and cis stilbene accounted for
100% of initial phenyldiazomethane).
1
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Ana Pereira et al.
FULL PAPERS
Scheme 2. General mechanistic picture for the epoxidation
of aldehydes catalyzed by TpxCuL and SR2.
Figure 2. ORTEP diagram of TpMsCu
ACTHNUTRGNEUNG(THT), 12. Hydrogen
atoms are omitted for clarity. Thermal ellipsoids are drawn
at the 30% probability level. Selected bond lengths [ꢅ] and
order to check if the low activities of TpMsCu in the
epoxidation reactions were due to the formation of
very stable TpMsCu
ACTHNUTRGNEU(GN sulfide) adducts, we have reacted
À
À
angles [8] for 12: Cu(1) N(1) 2.0889(15), Cu(1) N(3)
2.0460(15), Cu(1) N(5) 2.0836(14), Cu(1) S(1) 2.1775(5),
complex 4 with tetrahydrothiophene or dimethyl sul-
À
À
fide. After work-up (see the Experimental Section),
À
À
À
À
N(3) Cu(1) N(5) 92.09(6), N(3) Cu(1) N(1) 91.47(6),
N(5) Cu(1) N(1) 89.22(6), N(3) Cu(1) S(1) 123.21(4),
N(5) Cu(1) S(1) 133.05(4), N(1) Cu(1) S(1) 116.63(4).
we have isolated the novel compounds TpMsCu
ACTHNUTRGNE(NUG THT)
À
À
À
À
(12) and TpMsCu
(SMe2) (13) in good yields. These
À
À
À
À
two complexes have been characterized by 1H,
13C NMR and FT-IR spectroscopy. For instance, the
observed upfield shifts of the THT (two multiplets with one equiv. of THT [Eq. (6)], and the reaction
centered at d=1.00 and 1.66 ppm) and SMe2 (singlet mixture was monitored by 1H NMR spectroscopy
1
at d=0.87 ppm) in the H NMR spectra of 12 and 13, until an equilibrium mixture was reached. The equi-
respectively, can be explained as a consequence of the librium constant Keq has been estimated as 0.54(1) at
anisotropy generated by the p-systems of the mesityl room temperature by the ratio and the concentration
aromatic rings of the trispyrazolylborate, similar of both sulfides. From this value, similar stabilities for
to the effect observed, for instance, for the both adducts can be proposed. In contrast, when
protons of the ethylene ligand in the complex 1 equiv. of the bulkier PhSMe was added to a solution
TpMsCu
(CH2=CH2).[21]
ACTHNGUTRENNUG ACTHUNGTRENN(UGN SMePh)
of TpMsCu(SMe2), a small amount of TpMsCu
1
The structure of 12 was confirmed by an X-ray [Eq. (7)] was observed by H NMR spectroscopy at
single-crystal diffraction study, an ORTEP diagram
being shown in Figure 2. The complex crystallizes in
the orthorhombic space group Pna2(1). As found in
related compounds, TpMs binds in a tridentate fashion
to the copper center. The fourth metal coordination
position is occupied by the sulfur donor atom of the
THT, the copper being located in a distorted tetrahe-
À
dral environment. The Cu N(pz) bond distances and
N(pz) Cu N(pz) angles are within the range found
À
À
for other TpMsCuL complexes.[19,21,22] The distance
Cu S, [2.1775(5) ꢅ] is in the lower limit of the 2.158–
À
2.876 ꢅ range found in the Cambridge Structural Da-
tabase (CSD, version 5.31, May 2010)[23] for terminal the equilibrium mixture. A similar result was obtained
À
Cu(i) S bonds in thioether complexes, however this when 1 equiv. of PhSMe was added to a solution of
value is somewhat shorter than those found in Cu(I)- TpMsCu
N
THT complexes (2.181–2.369 ꢅ).[24]
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
sulfide exchange reactions. Thus,
a
TpMsCu
ACHTUNGTRENNUNG
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An Effective Dual Copper- and Sulfide-Catalytic System for the Epoxidation of Aldehydes
Epoxidation Reactions with in situ Generated
Phenyldiazomethane
vent. These two compounds, 2-o-tolyltetrahydrothio-
phene (15) and (2,3-dichloropropyl)benzene (16),
have been obtained in a catalytic manner following
We have also investigated the epoxidation of benzal- the above procedure in the absence of benzaldehyde
dehyde catalyzed by TpMsCu
AHCTUNGTRENNUNG
THT (20 mol%) using the strategy of the in situ gen- whereas the latter was obtained among other unchar-
eration of the diazo reagent. This can be accom- acterized products. Having determined the nature of
plished by heating the corresponding benzaldehyde the impurities, optimization of the epoxidation reac-
tosylhydrazone sodium salt at 608C in the presence of tion was achieved in two ways. Quantitative formation
1
benzyltriethylammonium chloride (NEt3BnCl) as of stilbene oxide was observed by H NMR (90% iso-
phase-transfer catalyst (PTC)[10] in 1,2-dichloroethane lated yield) when an excess of the diazo precursor
as solvent (Scheme 3). We used 4 for these studies was employed (1.5:1, diazo precursor:benzaldehyde).
given its higher stability at temperatures above ambi- On the other hand, such a precursor could be em-
ent.[25] Thus, after 24 h at 608C, an 80% yield of stil- ployed as the limiting reagent with methyl tert-butyl
À
bene oxide was obtained (cis:trans ratio 4:96) as de- ether as the solvent, for which low yields of C H
termined by H NMR spectroscopy of the reaction functionalization with EDA product has been repor-
1
crude. In addition to the main products, two sets of ted.[13c] Thus, when the reaction was performed in
resonances were also observed, and assigned to those 2 mL of MTBE at 608C [Eq. (10)], after 24 h, stilbene
characteristic of the compounds derived from Som- oxide (cis:trans ratio 3:97) was obtained in 95% yield
melet–Hauser rearrangement[10] of ylide and from the (determined by H NMR; 88% isolated yield). This
1
insertion of the carbene into the C H bond of the sol- activity surpasses[26] that of Cu
(acac)2 for this reaction
and compares well with that of dirhodium tetraace-
tate.
À
Conclusions
We have found that TpxCuL complexes, with organic
sulfides as cocatalyst, efficiently catalyze the reaction
of phenyldiazomethane and aldehydes to form epox-
ides, with activities exceeding or, at least, similar to
those of already reported rhodium-based systems. The
complex TpBr3Cu
ACTHNUTRGNEN(UG NCCH3) showed the highest activity
in these reactions, operating at mild conditions and
with remarkable short reaction times. The role of
copper–sulfide adducts as the catalyst resting state
Scheme 3. Epoxidation of benzaldehyde catalyzed by
TpMsCu
(THF), 4, via in situ generation of the diazo com-
pound, in ClCH2CH2Cl.
ACHTUNGTRENNUNG
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2947

Ana Pereira et al.
FULL PAPERS
bibliographical data[7d] and yields were calculated by integra-
tion of the corresponding peaks, using styrene as internal
standard, which was added with the deuterated solvent.
has been demonstrated, on the basis of equilibrium
constant values, isolation and structural determina-
tion. The strategy of in situ generation of the diazo re-
agent from benzaldehyde tosylhydrazone salt has led
to the conversion of benzaldehyde into stilbene oxide
in very high yields, avoiding the need of the previous
synthesis and isolation of the phenyldiazomethane.
Work aimed toward the development of the chiral
version of this system is currently underway in our
laboratory.
Preparation of TpMsCu
ACTHUNTGRENNG(U THT) (12)
The complex TpMsCu
ACTHNUTRGNEU(GN THF) (0.14 mmol) was dissolved in
CH2Cl2 (10 mL) in a Schlenk tube. The tetrahydrothiophene
(30 mmol) was added under a nitrogen atmosphere. The re-
action was stirred at room temperature for 1 h. The solvent
was removed under vacuum. Recrystallization using CH2Cl2
as solvent afforded complex TpMsCu
ACTHNUTRGNEUNG(THT) as a white solid;
yield: 0.101 mmol (72%). 1H NMR (400 MHz, C6D6): d=
1.00 (m, 4H, CH2) 1.66 (m, 4H, CH2), 2.10 (s, 9H, CH3),
2.14 (s, 18H, CH3), 5.98 (d, 3H, CH), 6.73 (s, 6H, CH), 7.76
(d, 3H, CH); 13C{1H} NMR (100 MHz, C6D6): d=20.9, 21.0,
29.4, 35.6, 104.3, 132.9, 134.9, 136.7, 138.0, 150.5. IR (KBr):
Experimental Section
General Methods
n(B H) =2440 cmÀ1; anal. calcd. for C40H48BCuN6S·1= CH2Cl2
All reactions and manipulations were carried out under an
oxygen-free nitrogen atmosphere by using Schlenk tech-
niques or under nitrogen atmosphere in an Mbraun glove-
box. All substrates were purchased from Aldrich and em-
ployed without further purification except aldehydes which
were distilled over MgSO4 prior to use. Solvents were dried
and degassed before use. Phenyldiazomethane,[27] homoscor-
pionate ligands,[28] copper complexes[28a] and benzaldehyde
tosylhydrazone sodium salt[10] were prepared according to
the literature methods. NMR spectra were recorded on
a Varian Mercury 400 MHz spectrometer. 1H NMR shifts
were measured relative to deuterated solvent peaks but are
reported relative to tetramethylsilane. Elemental analyses
were performed on a Perkin–Elmer Series II CHNS/O Ana-
lyzer 2400.
À
2
(761.74): C 63.86, H 6.48, N 11.03; found: C 64.27, H, 6.96,
N 10.62.
Preparation of TpMsCu
ACTHNUTRGEN(UGN SMe2) (13)
Following the above procedure, complex 13 was obtained as
white solid;: yield: 0.109 mmol (78%). 1H NMR
a
(400 MHz, C6D6): d=0.87 (s, 6H, CH3) 2.10 (s, 9H, CH3),
2.12 (s, 18H, CH3), 5.98 (d, 3H, CH), 6.74 (s, 6H, CH), 7.75
(d, 3H, CH); 13C{1H} NMR (100 MHz, C6D6): d=20.5, 20.6,
20.7, 103.9, 132.6, 134.5, 136.5, 137.7, 150.1. IR (KBr):
n(B H) =2419 cmÀ1; anal. calcd. for C38H46BCuN6S (693.23): C
À
65.84, H 6.69, N 12.12; found: C, 65.54; H, 6.90; N, 11.90.
Preparation of TpMsCu
ACTHNUGRTENUNG(SMePh) (14)
General Catalytic Procedure for the Epoxidation of
Aldehydes
Following the same procedure, complex 14 was obtained as
a white solid in presence of an excess of MeSPh. H NMR
1
(400 MHz, CD2Cl2): d=1.17 (s, 3H, SCH3) 1.87 (s, 18H,
CH3), 2.12 (s, 9H, CH3), 6.00 (d, 3H, CH), 6.24 (d, 2H,
CH), 6.62 (s, 6H, CH), 6.89 (t, 2H, CH), 7.08 (t, 1H, CH),
7.80 (d, 3H, CH); 13C{1H} NMR (100 MHz, CD2Cl2): d=
20.9, 21.2, 24.2, 104.8, 127.5, 128.4, 129.3, 131.1, 132.3, 135.1,
Phenyldiazomethane (0.5 mmol in 5 mL of toluene) was
added to a solution of TpBr3Cu
ACTHNUTRGNE(UNG NCMe) (0.005 mmol), di-
methyl sulfide (3 or 10 mol%) and aldehyde (0.5 mmol) in
CH2Cl2 (1 mL) over 1 h with the aid of a syringe pump.
Once the addition was completed the solvent was removed
1
137.5, 138.0, 139.1; IR (KBr): n(B H) =2444 cmÀ1. Due to the
À
under vacuum and reaction crude was analyzed by H NMR
excess of sulfide used a satisfactory elemental analysis could
not be obtained.
to determine the yield of the epoxide and the cis:trans ratio.
Signal assignments of protons of the products in the
1H NMR of the reaction mixture were based on the litera-
ture data[7d] and yields were calculated by integration of the
corresponding peaks, using furan as internal standard, which
was added with the deuterated solvent. Isolated yields were
obtained upon column chromatography (SiO2, petroleum
ether/triethylamine 100:1 as eluent).
General Procedure for the Study of Sulfide Exchange
Reactions
One equivalent of SR’2 was added to a solution of complex
TpMsCu
ACTHUNGTRNEUNG(SR2) in 0.6 mL of dichloromethane-d2, and the solu-
tion was transferred to an NMR tube that was sealed with
a Teflon stopper. The reaction mixture was monitored by
1H NMR until the equilibrium mixture was reached. The rel-
ative ratio of the sulfides in solution afforded the equilibri-
um constant Keq at room temperature for the exchange reac-
tion.
General Catalytic Procedure for the Epoxidation of
Ketones
To a solution of tetrahydrothiophene (1 mmol), complex
TpBr3Cu
ACHTUNGTRENNUNG(NCMe) (0.1 mmol) and the corresponding ketone
(1 mmol) in CH2Cl2 (1 mL) was added a solution of phenyl-
diazomethane (1.5 mmol in 1 mL of toluene) at 358C over
12 h by means of a syringe pump. After the addition was
completed the reaction mixture was stirred at room temper-
ature for 20 h. Signal assignments of protons of the products
1
in the H NMR of the reaction mixture were based on the
2948
asc.wiley-vch.de
ꢄ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2013, 355, 2942 – 2951

An Effective Dual Copper- and Sulfide-Catalytic System for the Epoxidation of Aldehydes
General Catalytic Procedure for the Epoxidation of
Benzaldehyde via in situ Generation of Phenyl-
diazomethane using 1,2-Dichloroethane as Solvent
Crystal Data for 12
A crystal of 12 with the size 0.10ꢆ0.09ꢆ0.06 mm3 was cov-
ered with perfluoropolyether oil (FOMBLINꢇ, Aldrich) and
mounted in a fiber loop. X-ray data were obtained with
Bruker SMART APEX II CCD area detector on a D8 goni-
ometer at 100 K, using graphite-monochromated and
To
sodium salt (0.75 mmol), benzyl triethylammonium chloride
(0.05 mmol) and TpMsCu
(THF) (0.005 mmol) were added
a stirred solution of benzaldehyde tosylhydrazone
AHCTUNGTRENNUNG
0.5 mm-Monocap-collimated
Mo-Ka
radiation
(l=
tetrahydrothiophene (0.1 mmol), aldehyde (0.5 mmol) and
anhydrous 1,2-dichloroethane (2 mL). The reaction mixture
was stirred at 608C for 24 h and then quenched by the addi-
tion of water and treated with dichloromethane. The aque-
ous layer was washed with dichloromethane and the com-
bined organic layers were dried over anhydrous Na2SO4, fil-
tered and concentrated under vacuum. The crude was ana-
lyzed by NMR spectroscopy to determine the composition
of the mixture and the diastereomeric ratio. Yields were cal-
culated by integration of the peaks using furan as internal
standard.
The use of this protocol with 1.25 mmol of benzaldehyde
tosylhydrazone sodium salt and 0.5 mmol of benzaldehyde
followed by final purification by column chromatography
(SiO2, petroleum ether/triethylamine 100:1 as eluent) pro-
vided stilbene oxide in 90% isolated yield (based on initial
benzaldehyde).
0.71073 ꢅ). Data were processed with the INTEGRATE
program of the APEX2 software[31] for reduction and cell re-
finement and corrected for absorption by multiscan method
applied by SADABS. The structure was solved by direct
methods and refined on F2 (SHELXTL).[32] Non-hydrogen
atoms were refined with anisotropic displacement parame-
ters and hydrogen atoms were introduced into the geometri-
cally calculated positions and refined riding on the corre-
sponding parent atoms. A summary of the fundamental crys-
tal and refinement data are given in the Supporting Infor-
mation. Crystallographic data (excluding structure factors)
have been deposited with the Cambridge Crystallographic
Data Centre under CCDC 935317. These data can be ob-
tained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
General Catalytic Procedure for the Epoxidation of
Benzaldehyde via in situ Generation of Diazo
Compound using Methyl tert-Butyl Ether as Solvent
Acknowledgements
We thank the MINECO (CTQ2011-24502 and CTQ2011-
28942-CO2-01), Fondos FEDER and Junta de Andalucꢀa
(P10-FQM-06292) for financial support. AP thanks the MEC
for a research fellowship.
The above procedure was repeated using methyl tert-butyl
ether as the solvent (2 mL). The crude was analyzed by
NMR spectroscopy, leading to 95% of epoxide, that was iso-
lated in 88% after column chromatography (SiO2, petroleum
ether/triethylamine 100:1 as eluent).
References
Functionalization of Tetrahydrothiophene with
TpMsCu
ACHTUNGTRENNUNG(THF)
[1] a) R. E. Parker, N. S. Isaacs, Chem. Rev. 1959, 59, 737–
799; b) J. G. Buchanan, H. Z. Sable, Selective Organic
Transformations, (Ed.: B. S. Thyagarajan), John Wiley
and Sons, New York, 1972, Vol. II, pp 1–95; c) A. K.
Yudin, Aziridines and Epoxides in Organic Synthesis,
1st edn., Wiley-VCH, Weinheim, 2006.
[2] a) J. Taunton, C. A. Hassig, S. L. Schreiber, Science
1996, 272, 408–411; b) L. H. Meng, R. Mohan, B. H. B.
Kwok, M. Elofsson, N. Sin, C. M. Crews, Proc. Natl.
Acad. Sci. USA 1999, 96, 10403–10408; c) N. Sin, L. H.
Meng, M. Q. W. Wang, J. J. Wen, W. G. Bornmann,
C. M. Crews, Proc. Natl. Acad. Sci. USA 1997, 94,
6099–6103; d) B. J. Albert, K. Koide, ChemBioChem
2007, 8, 1912–1915; e) J. Rokach, R. N. Young, M. Ka-
kushima, C.-K. Lau, R. Seguin, R. Frenette, Y. Guin-
don, Tetrahedron Lett. 1981, 22, 979–982; f) A. R.
Becker, J. M. Janusz, T. C. Bruice, J. Am. Chem. Soc.
1979, 101, 5679–5687; g) F. Sato, Y. Kobayashi, Synlett
1992, 849–857.
[3] a) A. Berkessel, C. Rollmann, F. Chamouleau, S. Labs,
O. May, H. Grçger, Adv. Synth. Catal. 2007, 349, 2697–
2704; b) T. M. Poessl, B. Kosjek, U. Ellmer, C. C.
Gruber, K. Edegger, K. Faber, P. Hildebrandt, U. T.
Bornscheuer, W. Kroutil, Adv. Synth. Catal. 2005, 347,
1827–1834; c) B. Seisser, I. Lavander, K. Faber, J. H.
Lutje Spelberg, W. Kroutil, Adv. Synth. Catal. 2007,
349, 1399–1404.
To a stirred solution of TpMsCu
ACTHNUTRGNE(UNG THF) (0.011 mmol), benzal-
dehyde tosylhydrazone sodium salt (1.13 mmol) and benzyl-
triethylammonium chloride (0.11 mmol), 2 mL of tetrahy-
drothiophene were added and the mixture was stirred at
608C for 4 h. The solvent was removed under vacuum. The
reaction mixture was filtered through celite and was ana-
1
lyzed by H NMR spectroscopy and then purified by flash
column chromatography, from which 2-o-tolyltetrahydro-
thiophene (15) was obtained as a yellow oil.
Functionalization of 1,2-Dichloroethane with
TpMsCu
ACHTUNGTRENNUNG(THF)
To a stirred solution of TpMsCu
ACTHNUTRGNE(UNG THF) (0.011 mmol), benzal-
dehyde tosylhydrazone sodium salt (1.13 mmol) and benzyl
triethylammonium chloride (0.11 mmol) was added 1,2-di-
chloroethane (2 mL). The reaction mixture was stirred at
608C for 4 h. The solvent was removed under vacuum. The
reaction mixture was filtered through celite and was ana-
lyzed by 1H NMR spectroscopy. Signals assignment of the
product 16 was based on the bibliographical data.[30]
Adv. Synth. Catal. 2013, 355, 2942 – 2951
ꢄ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
2949

Ana Pereira et al.
FULL PAPERS
[4] For a review of the Darzens reaction see: T. Rosen, in:
Comprehensive Organic Synthesis, (Eds.: B. M. Trost, I.
Fleming), Pergamon, Oxford, 1991, Vol. 2, pp 409–439.
For recent articles see: a) M. North, F. Pizzato, Lett.
Org. Chem. 2009, 67, 552–556; b) T. J. R. Achard, Y. N.
Belokon, J. Hunt, M. North, F. Pizzato, Tetrahedron
Lett. 2007, 48, 2961–2964; c) T. J. R. Achard, Y. N. Be-
lokon, M. Ilyin, M. Moskalenko, M. North, F. Pizzato,
Tetrahedron Lett. 2007, 48, 2965–2969; d) S.-i. Wata-
nabe, R. Hasebe, J. Ouchi, H. Nagasawa, T. Kataoka,
Tetrahedron Lett. 2010, 51, 5778–5780; e) W.-J. Liu, B.-
D. Lv, L.-Z. Gong, Angew. Chem. 2009, 121, 6625–
6628; Angew. Chem. Int. Ed. 2009, 48, 6503–6506; f) K.
Tanaka, R. Shiraishi, Green Chem. 2001, 3, 135–136;
g) V. K. Aggarwal, G. Hynd, W. Picoul, J.-L. Vasse, J.
Am. Chem. Soc. 2002, 124, 9964–9965; h) S. Arai, Y.
Suzuki, K. Tokumaru, T. Shioiri, Tetrahedron Lett.
2002, 43, 833–836; i) A. S. Demir, M. Emrullahoglu, E.
Pirkin, N. Akca, J. Org. Chem. 2008, 73, 8992–8997;
j) C. Palomo, M. Oiarbide, A. K. Sharma, M. C. Gon-
zꢁlez-Rego, A. Linden, J. M. Garcꢀa, A. Gonzꢁlez, J.
Org. Chem. 2000, 65, 9007–9012; k) Z. Rapi, T. Szabꢃ,
G. Keglevich, ꢈ. Szçllosy, L. Drahos, P. Bakꢃ, Tetrahe-
dron: Asymmetry 2011, 22, 1189–1196.
[5] For a review of epoxidation reactions, see: a) G. Gri-
goropoulou, J. H. Clark, J. A. Elings, Green Chem.
2003, 5, 1–7; b) B. S. Lane, K. Burgess, Chem. Rev.
2003, 103, 2457–2473; c) K. A. Jørgensen, Chem. Rev.
1989, 89, 431–458; d) T. Katsuki, Adv. Synth. Catal.
2002, 344, 131–147. For recent articles see: e) B. P. C.
Hereijgers, R. F. Parton, B. M. Weckhuysen, Catal. Sci.
Technol. 2012, 2, 951–960; f) C. Dinoi, R. Poli, L.
Perrin, L. Maron, Dalton Trans. 2012, 41, 1131–1133;
g) R. Yang, Y. Zhang, J. Zhao, Catal. Commun. 2011,
12, 923–926; h) M. Herbert, F. Montilla, A. Galindo, J.
Mol. Catal. A: Chem. 2011, 338, 111–120; i) A. D.
Chowdhury, A. Das, I. K. S. M. Mobin, G. K. Lahiri,
Inorg. Chem. 2011, 50, 1775–1785.
[6] a) N. Furukawa, Y. Sugihara, H. Fujihara, J. Org.
Chem. 1989, 54, 4222–4224; b) K. Julienne, P. Metzner,
J. Org. Chem. 1998, 63, 4532–4534; c) J. Zanardi, C.
Leriverend, D. Aubert, K. Julienne, P. Metzner, J. Org.
Chem. 2001, 66, 5620–5623; d) J. Zanardi, D. Lamazure,
S. Miniꢉre, V. Reboul, P. Metzner, J. Org. Chem. 2002,
67, 9083–9086; e) M. Davoust, J.-F. Briꢉre, P.-A. Jaffrꢉs,
P. Metzner, J. Org. Chem. 2005, 70, 4166–4169; f) S.
Miniꢉre, V. Reboul, P. Metzner, ARKIVOC 2005, 161–
177; g) A. Solladiꢂ-Cavallo, A. Diep-Vohuule, J. Org.
Chem. 1995, 60, 3494–3498; h) A. Diep-Vohuule, A.
Solladiꢂ-Cavallo, Tetrahedron: Asymmetry 1996, 7,
1783–1788; i) A. Solladiꢂ-Cavallo, L. Bouꢂrat, M. Roje,
Tetrahedron Lett. 2000, 41, 7309–7312; j) A. Solladiꢂ-
Cavallo, M. Roje, T. Isarno, V. Sunjic, V. Vinkovic, Eur.
J. Org. Chem. 2000, 1077–1080; k) A.-H. Li, L.-X. Dai,
X.- L. Hou, Y.-Z. Huang, F.-W. Li, J. Org. Chem. 1996,
61, 489–493; l) Y.-G. Zhou, X.-L. Hou, L.-X. Dai, L.-J.
Xia, M.-H. Tang, J. Chem. Soc. Perkin Trans. 1 1999,
77–80; m) A. Piccinini, S. A. Kavanagh, P. B. Connon,
S. J. Connon, Org. Lett. 2010, 12, 608–611; n) V. K. Ag-
garwal, J. G. Ford, A. Thompson, R. V. H. Jones,
M. C. H. Standen, J. Am. Chem. Soc. 1996, 118, 7004–
7005; o) V. K. Aggarwal, J. G. Ford, S. Fonquerna, H.
Adams, R. V. H. Jones, R. Fieldhouse, J. Am. Chem.
Soc. 1998, 120, 8328–8339; p) A.-H. Li, L.-X. Dai, V. K.
Aggarwal, Chem. Rev. 1997, 97, 2341–2372; q) V. K.
Aggarwal, C. L. Winn, Acc. Chem. Res. 2004, 37, 611–
620; r) E. M. McGarrigle, E. L. Myers, O. Illa, M. A.
Shaw, S. L. Riches, V. K. Aggarwal, Chem. Rev. 2007,
107, 5841–5883; s) D. M. Badine, C. Hebach, V. K. Ag-
garwal, Chem. Asian J. 2006, 1, 438–444; t) O. Illa, M.
Arshad, A. Ros, E. M. McGarrigle, V. K. Aggarwal, J.
Am. Chem. Soc. 2010, 132, 1828–1830; u) W. H.
Midura, M. Cypryk, Tetrahedron: Asymmetry 2010, 21,
177–186; v) A. Piccinini, S. A. Kavanagh, P. B. Connon,
S. J. Connon, Org. Lett. 2010, 12, 608–611; w) Y. Gui, J.
Li, C.-S. Guo, X.-L. Li, Z.-F. Lu, Z.-Z. Huang, Adv.
Synth. Catal. 2008, 350, 248–2487; x) T. Sone, A. Yama-
guchi, S. Matsunaga, M. Shibasaki, Molecules 2012, 17,
1617–1634; y) T. Sone, A. Yamaguchi, S. Matsunaga,
M. Shibasaki, J. Am. Chem. Soc. 2008, 130, 10078–
10079.
[7] a) V. K. Aggarwal, H. Abdel-Rahman, R. V. H. Jones,
H. Y. Lee, B. D. Reid, J. Am. Chem. Soc. 1994, 116,
5973–5974; b) V. K. Aggarwal, H. Abdel-Rahman,
R. V. H. Jones, M. C. H. Standen, Tetrahedron Lett.
1995, 36, 1731–1732; c) V. K. Aggarwal, M. Kalomiri,
A. P. Thomas, Tetrahedron: Asymmetry 1994, 5, 723–
730; d) V. K. Aggarwal, H. Abdel-Rahman, L. Fan,
R. V. H. Jones, M. C. H. Standen, Chem. Eur. J. 1996, 2,
1024–1030; e) V. K. Aggarwal, E. Alonso, G. Hynd,
K. M. Lydon, M. J. Palmer, M. Porcelloni, J. R. Studley,
Angew. Chem. 2001, 113, 1479–1482; Angew. Chem.
Int. Ed. 2001, 40, 1430–1433; f) V. K. Aggarwal, R. An-
gelaud, D. Bihan, P. Blackburn, R. Fieldhouse, S. J.
Fonquerna, G. D. Ford, G. Hynd, E. Jones, R. V. H.
Jones, P. Jubault, M. J. Palmer, R. D. Ratcliffe, H.
Adams, J. Chem. Soc. Perkin Trans. 1 2001, 2604–2622.
[8] a) V. K. Aggarwal, I. Bae, H.-Y. Lee, J. Richardson,
D. T. Williams, Angew. Chem. 2003, 115, 3396–3400;
Angew. Chem. Int. Ed. 2003, 42, 3274–3278; b) M. G.
Unthank, N. Hussain, V. K. Aggarwal, Angew. Chem.
2006, 118, 7224–7227; Angew. Chem. Int. Ed. 2006, 45,
7066–7069; c) V. K. Aggarwal, I. Bae, H.-Y. Lee, Tetra-
hedron 2004, 60, 9725–9733; d) J. A. Hadfield, K.
Gaukroger, N. Hirst, A. P. Weston, N. J. Lawrence,
A. T. McGown, Eur. J. Med. Chem. 2005, 40, 529–541;
e) P. Lupattelli, M. D’Auria, N. Di Blasio, F. Lenti, Eur.
J. Org. Chem. 2009, 141–145.
[9] a) E. J. Corey, M. Chaykovsky, J. Am. Chem. Soc. 1965,
87, 1353–1364; b) E. J. Corey, M. Chaykovsky, J. Am.
Chem. Soc. 1962, 84, 867–868.
[10] V. K. Aggarwal, E. Alonso, I. Bae, G. Hynd, K. M.
Lydon, M. J. Palmer, M. Patel, M. Porcelloni, J. Ri-
chardson, R. A. Stenson, J. R. Studley, J.-L. Vasse, C. L.
Winn, J. Am. Chem. Soc. 2003, 125, 10926–10940.
[11] a) S. Trofimenko, Scorpionates: The Coordination
Chemistry of Polypyrazolylborate Ligands, Imperial
College London, 1999; b) C. Pettinari, Scorpionates II:
Chelating Borate Ligands, Imperial College London,
2008.
[12] a) M. M. Dꢀaz-Requejo, T. R. Belderrain, S. Trofimen-
ko, P. J. Pꢂrez, J. Am. Chem. Soc. 2001, 123, 3167–3168;
b) M. M. Dꢀaz-Requejo, A. Caballero, T. R. Belderrain,
M. C. Nicasio, S. Trofimenko, P. J. Pꢂrez, J. Am. Chem.
2950
asc.wiley-vch.de
ꢄ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2013, 355, 2942 – 2951

An Effective Dual Copper- and Sulfide-Catalytic System for the Epoxidation of Aldehydes
Soc. 2002, 124, 978–983; c) M. M. Diaz-Requejo, M. A.
Mairena, T. R. Belderrain, M. C. Nicasio, S. Trofimen-
ko, P. J. Pꢂrez, Chem. Commun. 2001, 1804–1805.
[13] a) M. M. Dꢀaz-Requejo, T. R. Belderrain, M. C. Nica-
sio, S. Trofimenko, P. J. Pꢂrez, J. Am. Chem. Soc. 2002,
124, 896–897; b) A. Caballero, M. M. Dꢀaz-Requejo,
T. R. Belderrain, M. C. Nicasio, S. Trofimenko, P. J.
Pꢂrez, J. Am. Chem. Soc. 2003, 125, 1446–1447; c) A.
Caballero, M. M. Dꢀaz-Requejo, T. R. Belderrain, M. C.
Nicasio, S. Trofimenko, P. J. Pꢂrez, Organometallics
2003, 22, 4145–4150.
[14] M. E. Morilla, M. J. Molina, M. M. Dꢀaz-Requejo, T. R.
Belderrain, M. C. Nicasio, S. Trofimenko, P. J. Pꢂrez,
Organometallics 2003, 22, 2914–2918.
[15] M. E. Morilla, M. M. Dꢀaz-Requejo, T. R. Belderrain,
M. C. Nicasio, S. Trofimenko, P. J. Pꢂrez, Chem.
Commun. 2002, 2998–2999.
[23] a) F. H. Allen, Acta Crystallogr. Sect. B 2002, 58, 380–
388; b) I. J. Bruno, J. C. Cole, P. R. Edgington, M. Kess-
ler, C. F. Macrae, P. McCabe, J. Pearson, R. Taylor,
Acta Crystallogr. Sect. B 2002, 58, 389.
[24] a) S. Gambarotta, C. Floriani, A. Chiesi-Villa, C. Guas-
tini, J. Chem. Soc. Chem. Commun. 1983, 1156–1158;
b) S. Groysman, R. H. Holm, Inorg. Chem. 2009, 48,
621–627; c) H. Maelger, F. Olbrich, J. Kopf, D. Abeln,
E. Weiss, Z. Naturforsch B: Chem. Sci. 1992, 47, 1276–
1280.
[25] For instance, the synthesis of the g-lactam by intramo-
À
lecular C H insertion with N,N-diethyldiazoacetamide
as reagent and TpMsCu as catalyst requires 708C: C.
Martꢀn, T. R. Belderrain, P. J. Pꢂrez, Org. Biomol.
Chem. 2009, 7, 4777–4781.
[26] J. R. Fulton, V. K. Aggarwal, J. de Vicente, Eur. J. Org.
Chem. 2005, 1479–1492.
[27] D. S. Wulfman, S. Yousefian, J. M. White, Synth.
Commun. 1988, 18, 2349–2352.
[28] a) A. L. Rheingold, L. M. Liable-Sands, C. L. Incarvito,
S. Trofimenko, J. Chem. Soc. Dalton Trans. 2002, 2297–
2301; b) A. L. Rheingold, C. B. White, S. Trofimenko,
Inorg. Chem. 1993, 32, 3471–3477.
[29] J. L. Schneider, S. M. Carrier, C. E. Ruggiero, V. G.
Young, W. B. Tolman, J. Am. Chem. Soc. 1998, 120,
11408–11418.
[30] a) R. M. Denton, X. Tang, A. Przeslak, Org. Lett. 2010,
12, 4678–4681; b) C. E. Ayala, A. Villalpando, A. L.
Nguyen, G. T. McCandless, R. Kartika, Org. Lett. 2012,
14, 3676.
[31] APEX2 (version 2009.11 0). Program for Bruker CCD
X-ray Diffractometer Control, Bruker AXS Inc., Madi-
son, WI, 2009.
[32] G. M. Sheldrick, SHELXTL, version 6.14. Program for
solution and refinement of crystal structures, Universi-
tꢊt Gçttingen, Germany, 2000.
[16] M. J. Iglesias, M. C. Nicasio, A. Caballero, P. J. Pꢂrez,
Dalton Trans. 2013, 42, 1191–1195.
[17] a) V. K. Aggarwal, J. Richardson, Chem. Commun.
2003, 2998–2999; b) V. K. Aggarwal, S. Calamai, J. G.
Ford, J. Chem. Soc. Perkin Trans. 1 1997, 593–599;
c) V. K. Aggarwal, J. N. Harvey, J. Richardson, J. Am.
Chem. Soc. 2002, 124, 5747–5756; d) M. K. Lindvall,
A. M. P. Koskinen, J. Org. Chem. 1999, 64, 4596–4606;
e) H.-Y. Lee, I. Bae, K.-H. Min, Bull. Korean Chem.
Soc. 2007, 28, 2051–2055.
[18] M. J. Hatch, J. Org. Chem. 1969, 34, 2133.
[19] C. Martꢀn, M. Sierra, E. Alvarez, T. R. Belderrain, P. J.
Pꢂrez, Dalton Trans. 2012, 41, 5319–5325.
[20] See for instance: J. M. MuÇoz-Molina, W. M. Sameera,
E. ꢈlvarez, F. Maseras, T. R. Belderrain, P. J. Pꢂrez,
Inorg. Chem. 2011, 50, 2458–2467.
[21] C. Martꢀn, J. M. MuÇoz-Molina, A. Locati, E. Alvarez,
F. Maseras, T. R. Belderrain, P. J. Pꢂrez, Organometal-
lics 2010, 29, 3481–3489.
[22] K. Fujisawa, T. Ono, Y. Ishikawa, N. Amir, Y. Miyashi-
ta, K. Okamoto, N. Lehnert, Inorg. Chem. 2006, 45,
1698–1713.
Adv. Synth. Catal. 2013, 355, 2942 – 2951
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asc.wiley-vch.de
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