[(BINAP)Re(O)Cl3] as an efficient catalyst for olefination of chiral α-substituted aliphatic aldehydes

Article abstract of DOI:10.1016/j.jorganchem.2010.06.008

A convenient one-pot preparation of [(BINAP)Re(O)Cl₃] (6) is described. This complex was demonstrated to be an efficient catalyst for the olefination of aldehydes by reaction with α-diazo esters, with essentially quantitative yields and up to 98:2 geometric selectivity. The potential for using enantiopure [(BINAP)Re(O)Cl₃] (6) to promote an asymmetric kinetic resolution of racemic α-stereogenic aldehydes was investigated, but no enantiotopic discrimination was observed. Control experiments indicate that this lack of selectivity stems from the in-situ formation of a phosphonium ylide, which accounts for product formation in a non-metal associated reaction pathway.

Full text of DOI:10.1016/j.jorganchem.2010.06.008

Journal of Organometallic Chemistry 695 (2010) 2220e2224
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Journal of Organometallic Chemistry
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[(BINAP)Re(O)Cl3] as an efficient catalyst for olefination of chiral a-substituted
aliphatic aldehydes
,
b
Daniel Strand a , Tobias Rein
*
a Organic Chemistry, Department of Chemistry, Lund University, Box 124, SE-221 00 Lund, Sweden
b Process Chemistry R&D, AstraZeneca, SE-151 85 Södertälje, Sweden
a r t i c l e i n f o
a b s t r a c t
Article history:
A convenient one-pot preparation of [(BINAP)Re(O)Cl3] (6) is described. This complex was demonstrated
to be an efficient catalyst for the olefination of aldehydes by reaction with -diazo esters, with essentially
quantitative yields and up to 98:2 geometric selectivity. The potential for using enantiopure [(BINAP)Re
(O)Cl3] (6) to promote an asymmetric kinetic resolution of racemic -stereogenic aldehydes was inves-
tigated, but no enantiotopic discrimination was observed. Control experiments indicate that this lack of
selectivity stems from the in-situ formation of a phosphonium ylide, which accounts for product
formation in a non-metal associated reaction pathway.
Received 30 March 2010
Received in revised form
24 May 2010
Accepted 8 June 2010
Available online 17 June 2010
a
a
Keywords:
Alkenes
Ó 2010 Elsevier B.V. All rights reserved.
Homogenous catalysis
Rhenium
Wittig reactions
1. Introduction
workers recently addressed some of these concerns by presenting
a method for Wittig reactions which is catalytic in phosphine [5]. To
The ability to meet an increasing demand for complex molecules
in an efficient and sustainable manner relies on the development of
new synthetic methods and the strategies that they inspire.
Considerable efforts have been invested in the development of
asymmetric reactions where new stereogenic units are created, e.g.
selective bond formation to one of the enantiotopic faces of
a carbonyl or enolate. A different approach, to discriminate
between enantiotopic groups or enantiomers, is attractive as in
principle any process, also those that do not create new chirogenic
units, can be rendered enantioselective this way [1]. An example of
such a process is asymmetric olefination, e.g., the asymmetric
HornereWadswortheEmmons (HWE) reaction. Chiral phospho-
lower the cost, and ideally improve on operational convenience and
scalability, a method relying on readily available materials that
recycle the expensive chiral information in a catalytic cycle is
desired. Several reports on catalytic asymmetric HWE-type reac-
tions have been published [6], but a general, cheap, convenient and
efficient protocol remains elusive. The development of transition
metal catalyzed olefination reactions based on metalla-carbenes,
formed through catalytic decomposition of diazocompounds,
suggests new entries to an asymmetric olefination reaction [7,8].
Seminal work by Herrmann on MTO (methyltrioxorhenium)-cata-
lyzed olefinations serves as a useful starting point in this context.
This reaction has been shown to proceed via a metallaoxetane
intermediate, arising from cycloaddition of a Reecarbene to an
aldehyde (Scheme 1, [9a,b]). The metal is thus associated with the
substrate carbonyl in the proposed product-determining step.
Attaching chiral ligands to the metal in this process would create
a chiral environment at the reaction center that might discriminate
between enantiotopic carbonyl groups, either in the same substrate
molecule (asymmetric desymmetrization) or in different ones
(kinetic resolution), resulting in a catalytic asymmetric olefination
reaction. Chen and Zhang subsequently reported a detailed mech-
anistic study on a cationic Reebipyridyl catalyst formed from
decomposition of [Re2O7(bipy)] [9d]. With this catalyst the olefi-
nation reaction was shown to proceed via in-situ generation of
a Wittig-ylide, which accounts for product formation.
nates have been used to differentiate a-stereogenic enantiotopic
carbonyls, often with high yields and excellent geometric and dia-
stereoselectivies [2,3]. This strategy has played a key role in several
recent total syntheses of complex natural products with anti-
cancer activity [4]. The utility of asymmetric olefination reactions is
however currently hampered by the high cost of the most efficient
chiral phosphonates as well as by expensive and sensitive additives
(i.e. strong bases, crown ethers). A recent report by O’Brien and co-
* Corresponding author. Tel.: þ46 46 222 81 23; fax: þ46 46 222 82 09.
E-mail addresses: daniel.strand@organic.lu.se (D. Strand), tobias.rein@
astrazeneca.com (T. Rein).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.06.008

D. Strand, T. Rein / Journal of Organometallic Chemistry 695 (2010) 2220e2224
2221
compounds were used without further purification unless otherwise
indicated. TLC analyses were performed on aluminium-backed F254
gel plates, using UV and a solution of 5% phosphomolybdic acid in
ethanol for visualization. Flash chromatography was performed
using silica gel 60 (40e63
spectra were recorded on a 400 or 500 MHz instrument using the
O
LnRe O
EtO2C
CO2R
R2
catalyst
-N2
+
N2
R1
H
R1
R2
metallaoxetane
Catalysts:
1
2
m
m). Proton 1H and carbon 13C NMR
R1
CO2R
residual signals from CHCl3 at d7.26 and d77.0 as internal references,
respectively. 31P NMR was recorded on a 500 MHz instrument using
phosphoric acid as external reference. Optical rotations were deter-
mined using the sodium-D line (589 nm).
R2
3
O
Re
Cl
R1 = aromatic or aliphatic
R2 = H or CO2Me
Ph3P
Ph3P
Cl
Cl
Re
O
O
O
2.2. Representative procedure for Re-catalyzed olefinations
To a stirred solution of acrolein dimer 10 (54 ml, 0.53 mmol),
4
5
triphenylphosphine (46 mg, 0.18 mmol) and (þ)-[(BINAP)Re(O)Cl3]
Scheme 1. Rhenium catalyzed olefination of aldehydes.
(6) (9 mg, 0.009 mmol) in refluxing CH2Cl2 (2 mL) was added eth-
yldiazoacetate (EDA) (22 ml, 0.21 mmol) dissolved in CH2Cl2 (1 mL)
over 4 hours using a syringe pump, during which time the reaction
slowly turned brown. The reaction was refluxed a further 20
minutes and then cooled to room temperature. The volatiles were
removed under reduced pressure and the crude residues were
purified by flash chromatography (eluting with 3.13e6.25% EtOAc/
pentane) to give alkene 11 as a separable mixture of (E)- and (Z)
isomers, as a clear oil (27.5 mg, 84%).
(2E)-Ethyl 3-(3,4-Dihydro-2H-pyran-2-yl)acrylate (11) [19]. IR
(film) 2942 (m), 1720 (s), 1303 (m), 1180 (m), 1033 (m); 1H NMR
(500 MHz, CDCl3) 6.94 (dd, J ¼ 15.7, 4.3 Hz, 1H major isomer), 6.41
(td, J ¼ 6.6, 1.9 Hz, 1H), 6.08 (dd, J ¼ 15.7, 1.8, Hz, 1H), 4.77e4.70 (m,
1H), 4.55e4.49 (tdd, J ¼ 8.7, 4.3, 2.3 Hz, 1H), 4.22 (q, J ¼ 7.1 Hz, 2H),
2.17e2.06 (m, 1H), 2.05e1.95 (m, 2H), 1.77e1.66 (m, 1H), 1.31 (t,
J ¼ 7.2 Hz, 3H), 13C NMR (125 MHz, CDCl3), 166.8, 146.7, 143.7, 121.3,
101.1, 73.6, 60.9, 27.7, 19.5, 14.6; HPLC e.r. ¼ 50:50, Chiracel OD-RH
column, 60e25% MeCN/H2O over 30 min., 0.5 mL/min;
tR1 ¼14.38 min, tR2 ¼14.90 min; MS (ESI, M þ Hþ) ¼ calcd’ for
C10H15O3 183.1, found 183.
In addition to Re, several other metals like Mo, Co, Rh, and Fe
[10], exhibit catalytic activity in similar reactions. These processes
are typically described as proceeding through generation of ylides
[9,11].
Getting access to chiral analogs of MTO (5) is a synthetically
challenging task [12]. An alternative Re complex, also shown by
Herrmann to be an efficient catalyst of olefination reactions, is
[(PPh3)2Re(O)Cl3] [9b,13] (4). A protocol for olefinations catalyzed
by [(PPh3)2Re(O)Cl3] (4) using (EtO)3P as the reducing agent instead
of PPh3 was shown to simplify the workup as the solvents and
byproducts of this procedure are either volatile or water-soluble
[14]. The high stability of 4, paired with good behavior in catalysis
including low catalyst loadings, simple workups, good yields and
geometric selectivities makes it an attractive catalyst.
We hypothesized that [(BINAP)Re(O)Cl3] (6) might serve as
a chiral homolog of 4 in asymmetric olefination reactions (Fig. 1).
This complex is a known, air and shelf stable compound, previously
shown to exhibit good catalytic activity in oxidations of sulfides to
sulfoxides [15], and more recently in hydrosilylations of aldehydes
[16]. The X-ray structure of rac-6 was published by Parr et al. in
2005 [17].
(2E)-Ethyl 3-(1-Tosylpiperidin-2-yl)acrylate (13). IR (film) 2942
(m), 1720 (s), 1446 (m), 1263 (m), 1155 (s); 1H NMR (500 MHz,
CDCl3) 7.72e7.66 (m, 2H), 7.32e7.27 (m, 2H), 6.77 (dd, J ¼ 15.8,
5.3 Hz, 1H), 5.90 (dd, J ¼ 15.8, 1.9 Hz, 1H major isomer), 4.79e4.29
(m, 1H), 4.19 (q, J ¼ 7.1, 2H), 3.80e3.75 (d, J ¼ 13.4 Hz, 1H),
3.06e2.96 (m, 1H), 2.43 (s, 3H), 1.80e1.68 (m, 2H), 1.64e1.40 (m,
An achiral complex with a bidentate phosphine ligand, [(DPPE)
Re(O)Cl3] (7) was previously shown to be inactive in olefination
reactions [18], but given that the electronic properties of 6 would
resemble those of 4 more closely than those of the bisphenyl-alkyl
ligands of 7, this precedent was not decisive.
4H) (t, J ¼ 7.1 Hz, 3H); 13C NMR (101 MHz, CDCl3)
d 165.9, 145.3,
143.3, 137.4, 129.6, 127.2, 123.3, 60.5, 53.9, 41.8, 29.6, 24.7, 21.5, 19.3,
14.2; HPLC e.r. ¼ 50:50, Chiracel, OD-J column, 3% iPrOH/Hexanes,
0.9 mL/min; tR1 ¼ 29.46 min, tR2 ¼ 35.76 min; MS (ESI, M þ Hþ)
calcd’ for C17H24NO4S 338.1, found 338.
2. Experimental
rac-[BINAP]Re(O)Cl3] (rac-6). Perrhenic acid (224 mg, 53% in
H2O, 0.537 mmol) was dissolved in HCl (200 mL, conc.), and the
2.1. General methodology
resulting solution was added dropwise to a stirred suspension of
BINAP (318 mg, 0.426 mmol) in AcOH (6 mL). The resulting mixture
immediately turned green and a dark green precipitate was formed.
After 1 h, the reaction mixture was filtered and the filtrate washed
repeatedly with Et2O (3x) and cold CH2Cl2 (2x) to give 6, as dark
green microcrystals (205 mg, 41%): IR (KBr) 3054 (m), 2954 (m),
2856 (m), 1722 (m), 1434 (s); 1H NMR (500 MHz, CDCl3) 7.80e7.73
(m, 3H), 7.71e7.59 (m, 5H), 7.56e7.39 (m, 11H), 7.36 (ddd, J ¼ 8.2,
6.8, 1.2 Hz, 1H), 7.30e7.18 (m, 4H), 7.09e7.03 (m, 1H), 6.90 (d,
J ¼ 8.7 Hz, 1H), 6.87e6.76 (m, 4H), 6.59 (dt, J ¼ 8.1, 2.4 Hz, 2H); 31P
NMR (202 MHz, CDCl3), ꢀ17.8, ꢀ21.0.
Tetrahydrofuran (THF) was distilled from sodium/benzophenone
under a nitrogen atmosphere. Dichloromethane (CH2Cl2) was
distilled form CaH2 under a nitrogen atmostphere. All reactions were
carried out in oven-dried glassware. Commercially available
O
ReCl3
Ph
P
Ph
O
ReCl3
O
ReCl3
Ph
Ph
Ph
Ph
Ph
Ph
P
P
P
Ph
Ph
Ph
Ph
P
P
Ph
(þ)-[BINAP]Re(O)Cl3 (6) [20]. To a stirred solution of [(AsPh3)2Re
(O)Cl3] (9) (590 mg, 0.643 mmol) in CH2Cl2 (5 mL) was added
(þ)-(R)-BINAP (405 mg, 0.650 mmol). The resulting bright green
solution was stirred for 3 h after which it was concentrated to
0.5 mL. Addition of hexanes (7 mL) resulted in precipitation of 6,
which was collected by filtration. The solid was washed repeatedly
Ph
[(PPh3)2Re(O)Cl3] (4) (+)-[(BINAP)Re(O)Cl3] (6) [(DPPE)Re(O)Cl3] (7)
Fig. 1. Re (V) complexes with phosphine ligands.

2222
D. Strand, T. Rein / Journal of Organometallic Chemistry 695 (2010) 2220e2224
acetic acid gave rac-[(BINAP)Re(O)Cl3] rac-(6) as dark green
microcrystals. Filtration and washing with a small amount of cold
CH2Cl2 gave rac-6, homogenous as judged by 1H and 31P NMR in
moderate yield (41%).
The synthesis of enantiopure 6 is challenging due to its high
solubility compared to the racemate. When formed from (þ)-BINAP
(6) is a non-crystalline light green amorphous powder that rapidly
dissolves even in cold CH2Cl2 which precludes purification by
repeated washing or recrystallization. Since our one-pot procedure
gave slightly impure material we instead opted to prepare (þ)-6
using the two-step protocol via [(AsPh3)2Re(O)Cl3] (9) developed by
Grubbs [20].
3.2. Optimization of the olefination reaction
Scheme 2. One-pot synthesis of rac-6 and preparation of (þ)-6.
(5x) with Et2O to give rac-6 as a light green powder (200 mg, 33%),
With convenient access to both enantiopure (þ)-6 and the
cheaper rac-6 we turned to developing a protocol for their use in
olefination of aldehydes (Table 1). As aldehyde substrates, we chose
acrolein dimer 10 and sulfonamide aldehyde 13 [21]. Both of these
are sterically congested, aliphatic aldehydes. Aliphatic substrates are
challenging compared to electron poor aromatic aldehydes in metal
catalyzed olefinations, due to their propensity to form azines, with
reduced yields as a consequence. Aldehydes 10 and 13 also display
a series of functional groups such as enolizable carbonyls, an elec-
tron-rich vinyl ether, and a sulfonamide functionality. These struc-
tural motifs are useful in further synthetic elaborations of the
products, and also serve to probe the functional group tolerance of
the reaction. Both aldehydes 10 and 13 carry a heteroatom
substituted stereogenic center in the alpha position, a feature
readily soluble in CH2Cl2, and indistinguishable from rac-6 by NMR.
20
[
a]
¼ þ178.5 (c ¼ 0.4, CH2Cl2).
D
3. Results and discussion
3.1. Synthesis of Re-catalysts
Previous syntheses of rac-6 and similar compounds relied on
ligand exchange of the toxic triaryl arsine ligands of [(AsPh3)2Re(O)
Cl3] (9) [16]. To avoid the use of arsines we developed a convenient
single pot preparation of rac-6 that should be amenable to other
complexes of this type as well (Scheme 2). Addition of a mixture of
HCl and perrhenic acid (aq) to a suspension of rac-BINAP in glacial
Table 1
Optimization of the olefination of aldehydes 10, and 13.
CO2Et
O
O
O
O
N
O
OEt
N
H
10
11
12
CO2Et
conditions
O
O
Ts
N
Ts
Ts
N
N
N
OEt
N
H
14
15
13
Entry
Aldehyde (equiv.)
Catalyst (mol%)
Reducing agent
Solvent
THF
CH2Cl2/THF (1:2)
CH2Cl2/THF (1:2)
THF
CH2Cl2/THF (1:2)
THF
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
Temp.
(E):(Z)a
e.r.b
Alkene (NMR yield %)c,d
Azine (NMR yield %)c,d
1
2
3
10 (1.0)
10 (1.0)
10 (1.0)
10 (3.0)
10 (3.0)
10 (3.0)
10 (3.0)
10 (3.0)
10 (3.0)
10 (3.0)
13 (3.0)
13 (3.0)
6 (1)
4 (1)
6 (1)
6 (1)
6 (5)
6 (5)
6 (5)
6 (5)
(þ)-6 (5)
(þ)-6 (5)
(þ)-6 (5)
(þ)-6 (5)
P(OEt)3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
rt
rt
rt
rt
rt
rt
rt
e
e
<5%
e
ef
85:15
83:17
82:18
82:18
82:18
75:25
67:33
82:18
58:42
98:2
e
11 (w20)e
11 (13)
e
12 (63)
12 (40)
12 (41)
12 (35)
12 (45)
12 (52)
12 (<5)
e
4g
5h
6h
7h
8h
9h
10h
11h
12h
e
11 (13)
11 (57)
11 (39)
11 (51)
e
e
e
0 ꢁ
C
e
11 (15)
40 ꢁC
40 ꢁC
40 ꢁC
40 ꢁC
50:50
50:50
50:50
50:50
11 (100), 84i
11 (29)
P(OEt)3
PPh3
P(OEt)3
14 (100), 72i
14 (33)
15 (<5)
e
CH2Cl2
98:2
General Conditions: To a stirred solution of aldehyde, reductant (1 equiv) and catalyst in the solvent indicated was added EDA dropwise at the temperature indicated.
a
Determined by 1H NMR of the crude reaction mixture.
Determined by chiral HPLC.
b
c
Based on the limiting component.
d
Determined by 1H NMR of the crude reaction mixture using 1-methoxynaphthalene added upon reaction completion as internal standard.
e
Estimated from crude 1H NMR.
Not measured.
f
g
EDA was added as a CH2Cl2 solution over 1 h.
EDA was added as a CH2Cl2 solution over 4 h.
Isolated yield.
h
i

D. Strand, T. Rein / Journal of Organometallic Chemistry 695 (2010) 2220e2224
2223
designedto serve asahandletofacilitateenantiotopic discrimination
when carrying out the reaction with an enantioenriched catalyst.
Initial experiments with 6 as catalyst and (EtO)3P as the stoi-
chiometric reductant gave no detected product formation in the
reaction with acrolein dimer 10 (entry 1, Table 1) [22]. One reason
could be that complex 6 has a very low solubility in THF.
Exchanging (EtO)3P for PPh3 and using a mixture of THF and CH2Cl2
as the reaction medium, we obtained the desired alpha-beta
unsaturated ester in fair yield, using either 4 or 6 as catalyst, along
with substantial amounts of azine side-products (entries 2 and 3).
This result prompted us to optimize the process aiming to increase
the yield and suppress azine formation.
Scheme 4. Proposed pathway for the olefination of aldehydes catalyzed by 6.
We found that slow addition of EDA over 4 h with 5 mol%
catalyst in refluxing CH2Cl2 gave an essentially quantitative yield,
determined by crude NMR using an internal standard as reference,
and pushed the formation of azines below detectable levels. The
geometric selectivity for reaction with 10 under these conditions
was (E):(Z) ¼ 82:18 (Table 1, entry 9). Under the same conditions,
the reaction with amino-aldehyde 13 also gave complete conver-
sion into the desired product with an excellent geometric selec-
tivity (E):(Z) ¼ 98:2 (Table 1, entry 11). In most reactions, an excess
of aldehyde was used with applications in kinetic resolutions in
mind [23]. The isolated yields of 11 and 14 (entries 9 and 11, Table 1)
were somewhat diminished by difficult separation from excess
starting material.
When re-attempting the reaction under the optimized condi-
tions using triethyl phosphite instead of triphenylphosphine as
reducing agent (entries 10 and 12), we were able to obtain the
desired products 11 and 14 in fair yields albeit with considerably
diminished geometric selectivity for 11.
The catalytic performance in terms of yield using (þ)-[(BINAP)
Re(O)Cl3] (6) paralleled that of [(PPh3)2Re(O)Cl3] (4) with essen-
tially quantitative yields under the optimized conditions (e.g.
conditions used in entry 9). We note however that 4 is slightly more
active, resulting in less azine formation, under suboptimal condi-
tions (entries 2 and 3).
phosphine ligands. The lack of enantiodiscrimination in the reac-
tions catalyzed by (þ)-[(BINAP)Re(O)Cl3] (6) suggested to us that
the reaction proceeds through formation of an ylide, thus paral-
leling the mechanism proposed by Chen for [Re2O7(bipy)] catalysis
(Scheme 4). To gain further insight, a set of control experiments
were performed:
(i) A reaction in the absence of aldehyde resulted in formation of
a phosphonium ylide, Ph3P]CHCO2Et, as detected by crude 1H
NMR and ESI-MS.
(ii) Refluxing a mixture of 6 with a 100-fold excess of PPh3 in
CD2Cl2 for 4 h did not give detectable amounts of 4 (31P NMR).
(iii) A reaction in the absence of PPh3 using stochiometric amounts
of 6 or 4 gave no detected product formation.
(iv) Replicating the reactions in entries 9 and 11, Table 1, with
regards to solvent, concentration and temperature but using
Ph3PCHCO2Et instead of EDA/TPP gave, within limits of
detection, similar levels of geometric selectivity compared to
the metal catalyzed reactions.
It can be argued that trace amounts of 4, formed by ligand
exchange of BINAP with PPh3, can be the active catalyst in the
reaction. The combined observations that the catalytic performance
of 4 and 6 is within an order of magnitude (vide infra), and the
absence of significant formation of 4 upon prolonged heating of 6
with a 100-fold excess of PPh3, however supports 6 as an active
catalyst.
In addition, MTO (5) is known to olefinate aldehydes with
dimethyldiazomalonate as the carbene precursor [9a]. Reaction of
dimethyldiazomalonate (18) with 10 or 13 did not give any olefi-
nated product with 6 as the catalyst (Scheme 3). This result is in
agreement with what would be expected in a reaction that
generates an ylide, as (PPh3)]C(CO2Me)2 is known to be unreactive
towards aldehydes [9a].
Furthermore, the significant influence of the reductant (P(OEt)3
or PPh3) on the geometric selectivity in reactions with aldehyde 10
suggests that different reactive species (i.e., different ylides) are
involved in the two reactions [24].
Together, the results of these experiments are consistent with
a reaction proceeding through a metal catalyzed decomposition of
EDA and insertion into the phosphine (or phosphite) to generate an
ylide (Scheme 4). This is in contrast to the mechanism proposed for
the MTO-catalyzed reaction, but is in line with observations for
reactions catalyzed by many other metal complexes.
With an efficient olefination protocol at hand, we investigated
the possibility of using this reaction in a kinetic resolution of
racemic aldehydes 10 and 13 (entries 9e12). To this end, we were
not able to achieve any discrimination between the enantiomers of
either aldehyde, and all reactions using (þ)-[(BINAP)Re(O)Cl3] (6)
as catalyst gave racemic products regardless of aldehyde or
reductant. This result indicates that either the catalyst is not asso-
ciated with the reaction center in the stereo-discriminating step, or
that BINAP is replaced by achiral ligands on the metal center.
3.3. Mechanistic discussion
The mechanism of the olefination catalyzed by [(PPh3)2Re(O)
Cl3] (4) has not been discussed in detail previously. In the original
paper by Herrmann, it was assumed to proceed through a manifold
similar to that of the reaction catalyzed by MTO (5) through
a metallaoxedane (Scheme 1), via replacement of one of the
4. Conclusions
A convenient protocol for preparation of [(BINAP)Re(O)Cl3] (6)
was developed. This complex was found to be an efficient catalyst
for metal catalyzed olefination of aldehydes and constitute the first
example of a catalyst containing bis-phoshine ligands in this type of
Scheme 3. Unsuccessful olefination with 18 as the carbene precursor.

2224
D. Strand, T. Rein / Journal of Organometallic Chemistry 695 (2010) 2220e2224
[6] For lead examples see: (a) H.J. Bestmann, J. Lienert, Chem.-Ztg. (1970)
487e488;
(b) S. Arai, S. Hamaguchi, T. Shioiri, Tetrahedron Lett. 39 (1998) 2997e3000.
[7] A.M. Santos, C.C. Romao, F.E. Kuhn, J. Am. Chem. Soc. 125 (2003) 2414e2415.
[8] For review on metal catalyzed olefinations see: F.E. Kuhn, A.M. Santos Mini-
Rev. Org. Chem. 1 (2004) 55e64.
[9] (a) W.A. Herrmann, M. Wang, Angew. Chem. Int. Ed. 30 (1991) 1638e1641;
(b) W.A. Herrmann, P.W. Roesky, M. Wang, W. Scherer, Organometallics 13
(1994) 4531e4535 See also:
(c) X. Chen, X. Zhang, P. Chen, Angew. Chem., Int. Ed. 42 (2003) 3798e3801;
(d) X.Y. Zhang, P. Chen, Chem.dEur. J 9 (2003) 1852e1859.
[10] For lead references on various metals see: (a) X. Lu, H. Fang, Z. Ni, J. Orga-
nomet. Chem. 373 (1989) 77e84;
(b) M.Y. Lee, Y. Chen, X.P. Zhang, Organometallics 22 (2003) 4905e4909;
(c) G.A. Mirafzal, G.L. Cheng, L.K. Woo, J. Am. Chem. Soc. 124 (2002) 176e177;
(d) O. Fujimura, T. Honma, Tetrahedron Lett. 39 (1998) 625e626.
[11] For mechanistic discussions, see Ref. [8] and references cited therein.
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F.E. Kuhn, J. Organomet. Chem. 689 (2004) 3735e3740;
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3469e3479.
[13] (a) N.P. Johnson, C.J.L. Lock, G. Wilkinson, J. Chem. Soc. (1964) 1054e1066;
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transformation. Under optimized conditions, essentially quantita-
tive conversion into product in reactions with electron-rich alpha
substituted enolizable aliphatic aldehydes 10 and 13 was observed.
The described procedure using refluxing CH2Cl2 as reaction
medium with slow addition of EDA should be of value in similar
reactions where azine formation is a problem. The efficient product
formation in reactions with sensitive and reactive moieties such as
electron-rich vinyl ethers and sulphonamides suggests a wide
functional group tolerance. While the substrate scope was not
exhaustively studied, based on the proposed mechanism, we
expect the scope to parallel that of similar processes for less chal-
lenging substrates than 10 and 13.
The mechanistic investigation does not support using the title
reaction in kinetic resolutions of racemic aldehydes or desym-
metrizations of prochiral dialdehydes. However, the possibility of
using a chiral catalyst like (þ)-[(BINAP)Re(O)Cl3] (6) to deliver
a carbene to phosphines suggests opportunities in kinetic resolu-
tions of chiral (or prochiral) phosphines to form enantioenriched
ylides for use in e.g. asymmetric olefination reactions.
[14] B.E. Ledford, E.M. Carreira, Tetrahedron Lett. 38 (1997) 8125e8128.
[15] H.Q.N. Gunaratne, M.A. McKervey, S. Feutren, J. Finlay, J. Boyd, Tetrahedron
Lett. 39 (1998) 5655e5658.
[16] (a) R.H. Grubbs, F.D. Toste, Cal. Inst. Tech., USA, US 2002-16178, 2002. (b)
J.J. Kennedy-Smith, K.A. Nolin, H.P. Gunterman, F.D. Toste, J. Am. Chem. Soc.
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Acknowledgement
(c) For a review see W.R. Thiel, Angew. Chem., Int. Ed. 42 (2003) 5390e5392.
[17] M.L. Parr, C. Perez-Acosta, J.W. Faller, New. J. Chem. 29 (2005) 613e619.
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Chem.dEur. J. 10 (2004) 6313e6321.
We thank AstraZeneca Process R&D Södertälje, Sweden for
financial support.
[19] J. Adams, R. Frenette, M. Belley, F. Chibante, J.P. Springer, J. Am. Chem. Soc. 109
(2002) 5432e5437.
[20] A general procedure for the preparation of homochiral 6 was given by
Grubbs, but no analytical or experimental details were provided. See
Ref. [16a].
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more than trace amounts of olefinated products with despite varying the
source of this reagent. We are unable to explain this result.
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is 50% (conversion of 100% and 0% of each enantiomer, respectively), why at
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