Reduction of aromatic and aliphatic esters using the reducing systems MoO2(acac)2 or V(O)(OiPr)3 in combination with 1,1,3,3-tetramethyldisiloxane

Article abstract of DOI:10.1002/ejoc.201101016

An efficient reduction of aromatic and aliphatic esters with 1,1,3,3-tetramethyldisiloxane in combination with [MoO₂(acac) ₂] or [V(O)(OiPr)₃] is reported. In the former system, the presence of triphenylphosphane oxide allows high conversion and good isolated yield to be reached. For the latter system, no ligand is necessary to obtain the corresponding alcohols with similar results. 1,1,3,3-Tetramethyldisiloxane in association with [MoO₂(acac)₂] or [V(O)(OiPr)₃] was found to efficiently reduce aliphatic and aromatic esters. Copyright

Full text of DOI:10.1002/ejoc.201101016

FULL PAPER
DOI: 10.1002/ejoc.201101016
Reduction of Aromatic and Aliphatic Esters Using the Reducing Systems
MoO (acac) or V(O)(OiPr) in Combination with
2
2
3
1
,1,3,3-Tetramethyldisiloxane
[
a]
[a]
[a]
[a]
Leyla Pehlivan, Estelle Métay, Stéphane Laval, Wissam Dayoub,
[b]
[c]
[a]
Dominique Delbrayelle, Gérard Mignani, and Marc Lemaire*
Keywords: Synthetic methods / Reduction / Esters / Siloxanes / Molybdenum / Vanadium
An efficient reduction of aromatic and aliphatic esters with
,1,3,3-tetramethyldisiloxane in combination with [MoO
acac) ] or [V(O)(OiPr) ] is reported. In the former system, the
sion and good isolated yield to be reached. For the latter sys-
tem, no ligand is necessary to obtain the corresponding
alcohols with similar results.
1
(
2
-
2
3
presence of triphenylphosphane oxide allows high conver-
Introduction
some fatty esters is practiced industrially at relatively high
temperatures (200–300 °C) and high hydrogen pressures
[
9]
The reduction of esters is an important step in the syn- (200–300 atm) using transition-metal catalysts. The most
thesis of aldehydes, alcohols and ethers. This transforma- common catalyst used in this case is copper chromite. How-
[
10]
tion is important because esters are present in a large vari- ever, palladium over zinc oxide and ruthenium–platinum
[
11]
ety of natural products, and because alcohols are vital prod- over boehmite
have also been explored. Homogeneous
ucts in the chemical industry, where they have numerous systems with ruthenium complexes have also been em-
[
12–15]
uses such as in solvents, fuels, reagents and antifreeze.
ployed for this transformation.
Silicon chemistry combined with the use of organometal-
The most common approach to the preparation of
[
16]
alcohols from esters is the utilization of boron or aluminum lic complexes appears to be a good alternative.
hydride. Sodium borohydride can be used alone or with a and siloxanes have been employed with different metal
Silanes
[
1]
catalytic amount of cobalt.[
2–5]
Narasimhan et al. described sources such as Sb,
[17]
[18]
[19]
[20]
[21,22]
[23]
Rh,
Ru,
Mn,
Ti,
In,
[
24]
[25]
the reduction of esters with Zn(BH ) in the presence of Mo,
and Zn to afford alcohols, ethers, or aldehydes.
cyclohexene. The system LiBH /BH -N(iPr) has been Fluoride salts were also used to prepare alcohols.
4
2
[
6]
[26,27]
4
2
2
Un-
[
7]
used to reduce methyl benzoate and methyl octanoate.
fortunately, several silanes have been demonstrated to be
Brown et al. tested the reduction of esters with LiBH and harmful because they generate pyrophoric and toxic
4
[
28]
Ca(BH ) and found that, in both cases, good yields de- SiH4 gas.
4
2
pended on the nature of the solvent.[8] However, these hy-
drides are not appropriate for industry: they are expensive,
highly reactive with air and water, require careful handling,
and produce hydrogen gas in the reaction that increase the
risk of explosive ignition.
As a consequence, hydrosiloxanes (Si–O–Si) are consid-
ered to be interesting because the final waste material is
silica. Among these derivatives, polymethylhydrosiloxane
PMHS), as a 40-unit polymeric chain, was used with tita-
nium complexes by Buchwald and Lawrence. According to
(
An alternative reducing system involves the association
of hydrogen and a metal. Heterogeneous hydrogenation of
[29]
studies by Buchwald, the reduction of lactones to lactols
can be performed with [Cp TiX ] or [Cp Ti(OPh) ], and
2
2
2
2
[
30]
alcohols can be prepared from esters
with good selectivity toward alkenes, epoxides, and halides.
Chimie et Biochimie Moléculaires et Supramoléculaires The latter process was studied in stoichiometric quantities
ICBMS),
with [Ti(OiPr)4]
[a] Laboratoire de Catalyse et Synthèse Organique, Institut de
(
by Lawrence. The author commented on the similar reactiv-
CNRS, UMR 5246, Université Lyon 1,
[
31]
ity of [Zr(OEt)4],
which was found three years before,
4
6
3 boulevard du 11 novembre 1918, bat. CPE,
9622 Villeurbanne, France
and its ability to associate PMHS and a fluoride source to
reduce esters. PMHS was also employed with zinc com-
plexes by Mimoun; under these conditions, the use of so-
dium borohydride allows the formation of active zinc spe-
cies that are capable of reducing, for example, vegetal oils
Fax: +33-4-72431408
E-mail: marc.lemaire@univ-lyon1.fr
b] Minakem SAS,
[32]
[
[
1
45 Chemin des Lilas, 59310 Beuvry la Foret, France
c] Rhodia, Lyon Research Center,
5 Avenue des Frères Perret, BP 62, 69192 Saint-Fons Cedex,
France
8
[
33]
into fatty alcohols.
7400
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2011, 7400–7406

Reduction of Aromatic and Aliphatic Esters
1
,1,3,3-Tetramethyldisiloxane (TMDS; Scheme 1) also Table 1. Screening of catalysts for the reduction of methyl benzoate
1a).[
a]
(
constitutes a safe siloxane that is generated as a by-product
from industry and can be recycled for the water-repellent
treatment of materials.
Entry Metal
Catatyst loading Siloxane
Conv.[b]
[%]
[mol-%]
Scheme 1. 1,1,3,3-Tetramethyldisiloxane.
1
2
3
4
5
6
7
8
9
1
Mo(CO)
6
5
5
5
10
10
5
10
5
TMDS
PMHS
12
Ͼ99
0
34
Ͼ99
77
Ͼ99
Ͼ99
Ͼ99
0
MoO
MoO
2
(acac)
(acac)
2
To the best of our knowledge, TMDS has never been
used as a hydride source for the reduction of esters.
Whereas vanadium complexes have never been used in asso-
ciation with silanes for the reduction of organic functions,
2
2
W(CO)
6
Nb(OEt)
Nb(OEt)
V(O)(OiPr)
V(O)(OiPr)
V(O)(OiPr)
5
5
TMDS
PMHS
[
24,34,35]
Fernandes
MoO Cl ] with silanes. Aldehydes, ketones, imines, and es-
has studied the scope of the use of
3
3
3
[
2
2
10
5
ters have all been reduced to alcohols or amines. Since then,
other molybdenum complexes have been employed for
0
2 3 3
RuCl (PPh )
[
36,37,38]
[a] Reagents and conditions: 1a (2 mmol), 8 SiH (0.71 mL of
TMDS or 0.24 mL of PMHS), 1 m in toluene, 100 °C. [b] Deter-
mined by H NMR spectroscopic analysis after 24 h.
hydrosilylation.
In our laboratory, TMDS has already been employed to
efficiently reduce a range of functions such as phosphane
1
[
39]
[40]
[41]
[42]
[43]
oxides,
nitriles,
amides,
nitro,
acetals,
and
[
44]
ketones
depending on the nature of the metal catalyst.
plex (Table 1, entry 10). Further studies with PMHS were
We report herein a new method for the reduction of aro-
matic or aliphatic esters into alcohols using TMDS as re-
ducing agent in association with two different metal sources
to compare their reactivity.
[
45]
not pursued because of the formation of gels, which com-
plicated the clean isolation of the alcohol. TMDS was
therefore used as the hydride source.
The influence of the solvent was then examined with
5
mol-% [MoO (acac) ] (Table 2). Reactions were per-
2 2
formed at 100 °C for 18 h with an excess of hydride. The
best results were obtained with toluene, anisole, and cy-
Results and Discussion
At the beginning of our investigation, several catalysts clopentyl methyl ether (Table 2, entries 1, 5, and 7), whereas
were screened with TMDS or PMHS as reducing agent in either tetrahydrofuran (THF) or 2-methyltetra-
using methyl benzoate (1a) as a model substrate. When the hydrofuran (MeTHF), conversions were low (Table 2, en-
reactions were performed with [Co(acac) ], [Co(CN) ], tries 2 and 3). No conversion was observed in tert-butyl
3
6
[
[
[
Fe(OAc) ], [Fe(acac) ], [Mn(OAc) ], [Mn(acac) ], Pd/C, alcohol. Moderate conversions were observed with methyl-
2 3 2 3
PdCl (PPh ) ], [Pd(PPh ) ], [Pd (dba) ], [RhCl(PPh ) ], or cyclohexane and dimethyl carbonate (Table 2, entries 4 and
2
3 2
3 4
2
3
3 3
NiCl (PPh ) ] and either PMHS or TMDS, only starting 8).
2
3 2
materials were recovered; however the use of Mo, W, Nb,
V, and Ru complexes revealed some interesting results
Table 2. Influence of the solvent.[a]
(Table 1).
After 24 h reaction time, hexacarbonyl metal complexes
Table 1, entries 1 and 4) with TMDS or PMHS afforded
(
low conversions. However, because of their toxicity due to
the release of carbon monoxide, other molybdenum
catalysts were explored. The utilization of 5 mol-%
Entry
Solvent
Conv.[b] [%]
1
2
3
4
5
6
7
8
toluene
MeTHF
THF
methylcyclohexane
cyclopentyl methyl ether
tBuOH
anisole
dimethyl carbonate
Ͼ99
32
29
77
Ͼ99
0
[
MoO (acac) ] with TMDS allowed complete conversion to
2 2
be achieved, whereas when TMDS was replaced by PMHS
only starting material was recovered (Table 1, entries 2 and
3
). This result is remarkable considering that the Fernandes
[24]
Ͼ99
69
complex is known to reduce esters with PMHS.
Total
conversion into the corresponding alcohol was also ob-
[
%
a] Reagents and conditions: 1a (2 mmol), [MoO
2
(acac)
2
] (5 mol-
tained with 10 mol-% [Nb(OEt) ] with TMDS, and with
5
1
), 1 m solvent, 100 °C, 18 h. [b] Determined by H NMR spectro-
[
V(O)(OiPr) ] with both TMDS and PMHS (Table 1, en-
3
scopic analysis.
tries 5, 7, and 9). No effect on conversion was observed
when the amount of [V(O)(OiPr) ] was decreased (Table 1,
3
entry 8), however, the conversion reached only 77% with
Toluene was thus chosen as solvent, and the same
5
mol-% [Nb(OEt) ] (Table 1, entry 6). No conversion was [MoO (acac) ] catalyst was then employed to determine the
5
2
2
observed with PMHS in the presence of a ruthenium com- number of hydride equivalents required to reduce 1a.
Eur. J. Org. Chem. 2011, 7400–7406
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
7401

M. Lemaire et al.
FULL PAPER
In our previous investigation, the conversion was found entry 16). The use of a ruthenium complex in association
to be complete when 4 equiv. of TMDS (8 hydrides per ester with TMDS afforded 40% conversion into the alcohol, and
function) were utilized (Table 1 and Table 2). In theory, less the presence of added triphenylphosphane only slightly im-
hydride should be necessary to reduce an ester function into proved the conversion (Table 4, entries 17 and 18).
an alcohol. Thus, several experiments were conducted in
Table 4. Influence of the ligand.[a]
which the quantity of TMDS was reduced (Table 3). It was
found that, after 24 h, 40% of substrate 1a was converted
into the expected product with 0.5 equiv. of TMDS (1 hy-
dride; Table 2, entry 4). When the number of TMDS equiv-
alents were increased to 1.5 equiv. (3 hydrides; Table 2, en-
try 3), the conversion rate increased to 71%, and the con-
Entry
Metal
Cat. loading Ligand
T
Conv.
version was finally complete with 2 equiv. of TMDS
Table 2, entry 2). During these experiments, the formation
[°C] [%][
b]
[mol-%]
[mol-%]
(
1
2
3
4
5
6
7
8
9
MoO
MoO
MoO
MoO
MoO
MoO
MoO
MoO
MoO
MoO
MoO
MoO
Nb(OEt)
Nb(OEt)
V(O)(OiPr)3
V(O)(OiPr)
2
(acac)
(acac)
(acac)
(acac)
(acac)
(acac)
(acac)
(acac)
(acac)
(acac)
(acac)
(acac)
2
5
5
–
–
100
70
70
70
70
70
70
Ͼ99
29
56
of intermediates was never observed.
2
2
Table 3. Study on the number of necessary hydrides.[a]
2
2
5
5
5
PPh
PPh
PPh
3
(5)
(10)
(15)
2
2
3
71
Entry
TMDS [equiv.]
Conv.[b] [%]
2
2
3
Ͼ99
Ͼ99
Ͼ99
58
40
79
2
2
5
P(p-tolyl)
3
(15)
1
2
3
4
4
2
1.5
0.5
Ͼ99
Ͼ99
71
2
2
5
OPPh (10)
3
2
2
5
OPHCyPh (10) 70
2
2
5
dpppO (5)
70
70
100
100
70
40
1
0
2
2
2
1
OPPh
–
3
(4)
(2)
(4)
[
%
a] Reagents and conditions: 1a (2 mmol), [MoO
2
(acac)
2
] (5 mol-
11
12
13
2
2
48
), toluene (1 m), 100 °C. [b] Determined by 1H NMR spectro-
1
10
2
OPPh
–
Ͼ99
Ͼ99
11
Ͼ99
Ͼ99
40
2
2
3
scopic analysis.
5
14
5
OPPh
3
70
To achieve a decrease the required catalyst loading, the 15
effect of the ligand was examined (Table 4). No conversion 16
10
1
5
–
–
–
100
100
100
100
3
1
7
RuCl
RuCl
2
(PPh
(PPh
3
)
3
of 1a into 1b was observed when molybdenum derivatives
were mixed with urea, benzonitrile, pyridine, bipyridine, or
dimethylethylenediamine. However, with the molybdenum
complex (Table 4, entries 1–12), the presence of a phospho-
rus ligand allowed a reduction of the temperature from
18
2
3
)
3
5
3
PPh (10)
54
[
a] Reagents and conditions: 1a (2 mmol), TMDS (2 equiv.), tolu-
1
ene (1 m), 100 °C, 24 h. [b] Determined by H NMR spectroscopic
analysis.
100–70 °C when 5 mol-% catalyst was employed. Optimal
Based on these results, the two optimal conditions
conversion was obtained with 15% triphenylphosphane (cf. (1 mol-% [MoO (acac) ] or [V(O)(OiPr) ]) were considered
2
2
3
Table 4, entries 3, 4, and 5). Phosphorus NMR analysis of for the reduction of aromatic and aliphatic substrates. Both
the reaction mixture containing PPh , [MoO (acac) ], and systems {[MoO (acac) ]/OPPh /TMDS (conditions A) and
3
2
2
2
2
3
TMDS revealed the formation of triphenylphosphane ox- [V(O)(OiPr) ]/TMDS (conditions B)} were applied to aro-
3
ide. Based on this observation, this compound was consid- matic esters to give the corresponding alcohols. These two
ered as a ligand. The reduction of triphenylphosphane ox- systems of reduction were both found to efficiently reduce
ide in the presence of Si–H has already been reported, how- methyl benzoate with total conversion into the alcohol after
ever, the formation of triphenylphosphane was controlled 18 h; benzyl alcohol (1b) was isolated with 90% yield
and was not detected when triphenylphosphane oxide was (Table 5, entry 1). The presence of a donating group in the
mixed with TMDS and [MoO (acac) ]. The utilization of para-position did not affect the efficiency of the reaction;
2
2
more basic phosphanes seems not to be a decisive param- the reduction of esters 2a and 3a was complete after 16 h
eter (Table 4, entries 6 and 7). Moreover, the use of a biden- with [MoO (acac) ] (Table 5, entries 2 and 3). We noticed,
2
2
tate ligand was less favorable (Table 4, entry 9). When the however, that the use of [V(O)(OiPr) ] was less efficient for
3
quantity of [MoO (acac) ] was decreased to 2 mol-%, 79% the reduction of methyl p-methoxybenzoate (2a) and that
2
2
conversion of 1b was observed (Table 4, entry 10). Further conversion was not complete after 16 h. With an electron-
studies revealed that conducting the reaction at 100 °C, withdrawing group such as Br or CF , present in the sub-
3
with 1 mol-% [MoO (acac) ] in the presence of OPPh is strate, total conversion into the corresponding benzyl
2
2
3
sufficient to reduce 1a (Table 4, entry 12). Performing the alcohols 4b and 6b was obtained after 19 and 24 h, respec-
reduction with [Nb(OEt) ] gave less satisfactory results be- tively (Table 5, entries 4 and 6). Conditions A and B were
5
cause total conversion was only obtained with 5 mol-% cat- then applied to methyl p-nitrobenzoate (5a). It was interest-
alyst; when the catalyst loading was decreased to 2 mol-% ing to note that Conditions A were not suitable for the re-
with the addition of OPPh , the conversion rate was low duction of the ester function but, instead, allowed the par-
3
(Table 4, entries 13 and 14). Finally, it was found that the tial reduction of the nitro function into the corresponding
use of 1 mol-% [V(O)(OiPr) ] gave results that were similar amine, which was isolated with 53% yield. The result ob-
3
to those obtained with [MoO (acac) ] but, in this case, no tained in this case with the molybdenum complex can be
2
2
[
24]
ligand was necessary to reduce methyl benzoate 1a (Table 3, compared to results obtained by Fernandes . Under Con-
7402
www.eurjoc.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2011, 7400–7406

Reduction of Aromatic and Aliphatic Esters
2 2 3
Table 5. Reduction of aromatic esters. Conditions A: substrate (8 mmol), [MoO (acac) ] (1 mol-%), OPPh (2 mol-%), TMDS (2 equiv.),
toluene (2 m). Conditions B: substrate (8 mmol), [V(O)(OiPr) ] (1 mol-%), TMDS (2 equiv.), toluene (2 m).
3
1
[
a] Determined by H NMR spectroscopic analysis (n.d.: not determined). [b] Crude product obtained under Conditions A were purified
by flash chromatography. [c] Isolated as the hydrochloride salt. [d] After 60 h with 10% catalyst, only 47% conversion was observed.
ditions B, neither ester nor nitro function was reduced reached 48%; the corresponding alcohol was not isolated.
(Table 5, entry 5).
From these results, it is difficult to conclude anything con-
The presence of a nitrogen atom in the substrate seems cerning the efficiency of these two conditions. Indeed, sim-
to block the reduction of esters. The application of p-cya- ilar results were obtained for the reduction of aromatic es-
nomethylbenzoate (7a) confirmed that no reduction oc- ters with molybdenum or vanadium complexes.
curred under either conditions when a nitrogen atom is
To increase the scope of this methodology, the reduction
present on the substrate (Table 5, entry 7). Furthermore, of aliphatic esters was studied. Initial tests were conducted
reduction of an ester containing an aminothiophene moiety on aliphatic substrates containing an aromatic ring. Sur-
also failed, and no reduction occurred. With substrates con- prisingly, the reaction progressed slowly under Condi-
taining a ketone group in the para-position, no reduction tions A [MoO (acac) ] (Table 6, entries 10 and 11). For
2
2
was observed under Conditions B [V(O)(OiPr) ], whereas methyl 3-thiopheneacetate (10a) and methyl phenylacetate
3
reduction of the ketone was predominant under Condi- (11a), alcohols were obtained with total consumption of the
tions A (Scheme 2).
esters after 48 h, whereas reduction with vanadium complex
required 22–26 h reaction time. However, tridecanol (12b)
was obtained faster, with 20 h of reaction time being suf-
ficient to completely convert the ester under both condi-
tions (Table 6, entry 12). These results can be compared to
those obtained using the Fernandes method in which 80%
yield of decanol was isolated in 20 h. Reaction with methyl
oleate (13a) was also efficient, giving the corresponding
Scheme 2. Reduction of a ketone under Conditions A.
Finally, the vanadium complex showed a slight improve- oleic alcohol (13b) after 24 h in good isolated yield. The
1
ment over the use of the molybdenum catalyst for the re- double bond was not reduced, but H NMR and GC-MS
duction of ethyl p-hydroxybenzoate (9a). Under Condi- analyses revealed that an isomerization took place, with
tions A, less than 5% of the desired alcohol was detected, 55% Z and 45% E isomer being obtained. It was noticed,
whereas Conditions B allowed a conversion of 21% to be however, that in the presence of 5 mol-% molybdenum cata-
achieved (Table 4, entry 9). By increasing the catalyst load- lyst, a greater degree of isomerization occurred [20% Z and
ing as well as the reaction time, the conversion still only 80% E]. A test of the reduction conditions with racemic
Eur. J. Org. Chem. 2011, 7400–7406
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
7403

M. Lemaire et al.
2 2 3
Table 6. Reduction of aliphatic substrates. Conditions A: substrate (8 mmol), [MoO (acac) ] (1 mol-%), OPPh (2 mol-%), TMDS
FULL PAPER
3
(2 equiv.), toluene (2 m). Conditions B: substrate (8 mmol), [V(O)(OiPr) ] (1 mol-%), TMDS (2 equiv.), toluene (2 m).
1
[
a] Determined by H NMR spectroscopic analysis (n.d: not determined). [b] Crude product obtained under Conditions A were purified
by flash chromatography. [c] Crude product obtained under Conditions B were purified by flash chromatography.
methyl mandelate (14a) was conducted, however, the reac- on the molecule. However, both aliphatic and aromatic es-
tion is very slow; only 48% conversion into the alcohol was ters can be reduced with good to high yields. The mecha-
observed after 18 h reaction. Conversion with vanadium nism of the reaction will be investigated in due course.
was not determined because of difficulties in its evaluation
1
by H NMR spectroscopy. The reduction of ethyl cinna-
mate (15a) required 72 h to obtain the corresponding Experimental Section
alcohol 15b with [MoO (acac) ] and 48 h with [V(O)(OiPr)
2
2
General Information: All reagents were obtained commercially.
3]
. With aliphatic substrates, the difference between both
TMDS (97%) was purchased from Aldrich, and [MoO
2 2
(acac) ] and
catalysts was more pronounced, with the reaction appar-
ently proceeding faster in the presence of vanadium com-
plex.
[
V(O)(OiPr) ] from Strem Chemicals. All reagents and reactants
3
were used without further purification. All reactions were per-
formed under an inert atmosphere (argon) in sealed tubes. All com-
The mechanism of the reduction of phosphane oxide in pounds were characterized by spectroscopic data. The NMR spec-
1
tra were recorded with a Bruker ALS or DRX 300 ( H: 300 MHz,
the presence of TMDS and [Ti(OiPr) ] was previously inves-
tigated. From the analysis, the formation of a silyl radical
4
1
3
[
39]
C: 75 MHz), chemical shifts are expressed in ppm, J values are
given in Hz; CDCl was used as solvent. GC-MS were measured
with a focus DSQ instrument using electronic ionization with a
DBS phase; column dimensions 30 mϫ0.25 mm (initial tempera-
ture 70 °C; initial time 2 min; rate 15 deg/min).
3
was proposed as a key step in the reduction. For this work,
and based on literature data,[
46]
the formation of a metal
hydride Mo–H from silane and molybdenum complex can
be postulated. This species could reduce the ester to the
aldehyde, which could then be further reduced to the
General Procedures
alcohol. Because, to the best of our knowledge, no vana- Procedure A: To a solution of ester (8 mmol) in anhydrous toluene
dium complex has previously been used with silane, to (1.5–2 m) were added [MoO (acac) (1 mol-%, 0.08 mmol,
(2 mol-%, 0.16 mmol, 44.5 mg), and TMDS
2 equiv., 16 mmol, 2.8 mL). The reaction mixture was stirred at
00 °C for 15–48 h, depending to the substrate. Thereafter, THF
10 mL) and TBAF (1 m in THF, 1 equiv., 8 mL) were added and
the mixture was stirred for 2 h. The organic phase was recovered
with dichloromethane and washed with water, dried with MgSO
2
2
]
3
(
1
2.6 mg), OPPh
3
understand the mechanism implied in these cases, a more
complete study is in progress.
(
Conclusions
4
,
and the solvents were removed in vacuo. The crude product was
purified by column chromatography on silica gel (cyclohexane/ethyl
acetate, 99.9:0.1 to 90:10) to yield the alcohol.
For the first time, a vanadium complex has been em-
ployed for the reduction of an organic function. We have
demonstrated that TMDS can be used for the reduction
of esters in the presence of catalytic quantities of metallic Procedure B: Same procedure as A was followed. [MoO
and OPPh were replaced by [V(O)(OiPr) ].
ployed for this transformation. To date, the only limitation Benzyl Alcohol (1b) [100-51-6]: Yellow oil. 1H NMR (300 MHz,
2 2
(acac) ]
complex. Both [MoO (acac) ] and [V(O)(OiPr) ] can be em-
3
3
2
3
3
1
3
that has been found was for substrates with nitrogen atoms CDCl
3
): δ = 7.38–7.29 (m, 5 H), 4.70 (s, 2 H) ppm. C NMR
7404
www.eurjoc.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2011, 7400–7406

Reduction of Aromatic and Aliphatic Esters
(
1
5
75 MHz, CDCl
3
): δ = 141.0 (CH), 133.3 (Cq), 128.5 (2ϫ CH),
27.6 (CH), 127.1 (2ϫCH), 64.8 (CH ) ppm. GC-MS: t
.32 min; m/z (%) = 108 (72) [M ], 137 (31), 79 (100), 77 (62)
Tridecanol (12b) [112-70-9]: Colorless oil. 1H NMR (300 MHz,
CDCl ): δ = 3.64 (t, J = 6.4 Hz, 2 H), 1.54–1.60 (m, 2 H), 1.19–
1.39 (m, 21 H), 0.88 (t, J = 6.4 Hz, 3 H) ppm. C NMR (75 MHz,
OH]. IR (ATR): ν˜ max = 3311, 3064, 3030, 2923, 285, CDCl3): δ = 62.9 (CH ), 33.0 (CH ), 32.2 (CH ), 30.0 (CH ), 29.7
), 22.9 (CH ), 14.3 (CH ) ppm. GC-MS: t
.49 min; m/z (%) = 183 (0.5) [M – OH], 140 (8), 111 (23), 97
37), 83 (54), 69 (60), 55 (57). IR (ATR): ν˜ max = 3329, 2921, 2852,
2
R
=
3
+
·
13
+
·
[M
– CH
2
2
2
2
2
–1
1
496, 1453, 1207, 1011, 911, 806, 732, 695 cm .
(CH
9
(
2
), 26.1 (CH
2
2
3
R
=
+
·
1
4
-Methoxybenzyl Alcohol (2b) [105-13-5]: Colorless oil. H NMR
(300 MHz, CDCl
3
): δ = 7.29 (d, J = 8.9 Hz, 2 H), 6.89 (d, J =
–
1
1466, 1056, 720 cm .
1
3
8
.7 Hz, 2 H), 4.62 (s, 2 H), 3.81 (s, 3 H), 1.58 (br. s, 1 H) ppm.
C
NMR (75 MHz, CDCl
3
): δ = 158.9 (Cq), 133.3 (Cq), 128.6 (2 CH), Oleyl Alcohol [143-28-2] and (E)-Octadec-9-enol (13b) [506-42-3]:
1
1
13.8 (2 CH), 64.3 (CH
m/z (%) = 138 (100) [M ], 137 (31), 109 (39), 107 (10) [M
CH OH], 77 (11). IR (ATR): ν˜ max = 3328, 2934, 2835, 1611, 1512,
2
), 55.1 (CH
3
) ppm. GC-MS: t
R
= 7.89 min;
3
Colorless oil. H NMR (300 MHz, CDCl ): δ = 5.34–5.47 (m, 2
+
·
+·
–
H), 3.63 (t, J = 6.6 Hz, 2 H), 1.92–2.09 (m, 3 H), 1.56 (t, J =
6.6 Hz, 2 H), 1.17–1.40 (m, 24 H), 0.88 (t, J = 6.4 Hz, 3 H) ppm.
C NMR (75 MHz, CDCl3): δ = 130.6 (CH), 130.1 (CH), 62.9
2
–1
13
1
243, 1172, 1030, 1003, 813 cm .
(
(
1
3
CH
CH
2
), 33.0 (CH
), 23.0 (CH
2
), 32.2 (CH
2
), 30.0–29.4 (CH
2
), 27.5 (CH
= 13.75 (Z),
O]. IR (ATR): ν˜ max
2
), 26.1
4
-Methylbenzyl Alcohol (3b) [589-18-4]: White crystalline solid;
2
2
), 14.3 (CH
3
) ppm. GC-MS: t
R
1
m.p. 64 °C. H NMR (300 MHz, CDCl
H), 7.18 (d, J = 7.9 Hz, 2 H), 4.66 (s, 2 H), 2.37 (s, 3 H), 1.61
br. s, 1 H) ppm. 13C NMR (75 MHz, CDCl
): δ = 138.2 (Cq),
37.2 (Cq), 129.2 (2 CH), 127.2 (2 CH), 64.8 (CH
3
): δ = 7.27 (d, J = 7.9 Hz,
+·
3.78 min (E); m/z (%) = 250 (5) [M – H
328, 2921, 2852, 1465, 1056, 965 cm .
2
=
2
(
1
(
(
(
1
–1
3
), 21.3 1-Phenyl-1,2-ethanediol (14b) [93-56-1]: Yellow crystalline solid;
2
+
·
1
CH
20), 107 (100) [M – CH
70), 77 (32). IR (ATR): ν˜ max = 3347, 2921, 1517, 1444, 1340, OH) ppm. C NMR (75 MHz, CDCl
3
) ppm. GC-MS: t
R
= 6.38 min; m/z (%) = 122 (100) [M ], 121
], 93 (32), 91 (62) [M – CH OH], 79
3 2
m.p. 63 °C. H NMR (300 MHz, CDCl
3
): δ = 7.36–7.30 (m, 5 H),
+
·
+·
4.82 (dd, J = 3.6, 8.1 Hz, 1 H), 3.78–3.63 (m, 2 H), 2.49 (br. s, 2
1
3
3
): δ = 140.8 (Cq), 128.7 (2ϫ
CH), 128.1 (Cq), 126.4 (2ϫ CH), 75.0 (CH), 68.2 (CH ) ppm. GC–
–1
0207, 1453, 1027, 1012, 802 cm .
2
+
·
+·
MS: t
CH OH], 79 (100), 77 (72). IR (ATR): ν˜ max = 3199, 2932, 1148,
340, 1033, 1023, 747, 1027, 697 cm .
R
= 7.98 min; m/z (%) = 138 (6) [M ], 107 (88) [M
–
4
7
7
-Bromobenzyl Alcohol (4b) [873-75-6]: White crystalline solid; m.p.
2
1
7 °C. H NMR (300 MHz, CDCl
3
): δ = 7.48 (d, J = 8.3 Hz, 2 H),
–1
1
1
3
.24 (d, J = 7.9 Hz, 2 H), 4.66 (s, 2 H), 1.57 (br. s, 1 H) ppm.
C
1
Cinnamyl Alcohol (15b) [104-54-1]: Yellow oil. H NMR (300 MHz,
CDCl ): δ = 7.41–7.21 (m, 5 H), 6.63 (d, J = 16 Hz, 1 H), 6.42–
6.33 (m, 1 H), 4.33 (d, J = 7.2 Hz, 2 H), 1.55 (br. s, 1 OH) ppm.
NMR (75 MHz, CDCl
3
): δ = 140.0 (Cq), 131.9 (2ϫ CH), 128.9
(
(
2ϫ CH), 121.7 (Cq), 64.7 (CH
2
) ppm. GC-MS: t
R
= 8.36 min; m/z
3
%) = 186 (24) [M+· – H], 157 (8) [M – CH
+·
+·
2
OH], 107 (66) [M
–
1
3
C NMR (75 MHz, CDCl
3
): δ = 136.9 (Cq), 130.9 (CH), 128.8 (2
Br], 79 (100), 77 (70). IR (ATR): ν˜ max = 3260, 2921, 1591, 1486,
1
–1
CH), 128.5 (Cq), 127.7 (CH), 126.6 (2CH), 63.3 (CH ) ppm. GC-
MS: t
446, 1403, 1021, 1007, 827, 791 cm .
2
+
·
R
= 7.87 min; m/z (%) = 134 (82) [M ], 115 (50), 105 (50),
Methyl 4-Aminobenzoate Hydrochloride (5b) [619-45-4]: Beige solid.
9
1
2 (100), 91 (83), 78 (58). IR (ATR): ν˜ max = 3315, 2923, 2854, 1494,
448, 1091, 1008, 965, 732, 691 cm .
1
H NMR (300 MHz, CD
d, J = 8.9 Hz, 2 H), 3.94 (s, 3 H) ppm. C NMR (75 MHz,
CD OD): δ = 168.0 (Cq), 137.4 (Cq), 133.3 (Cq), 132.8 (2ϫ CH),
25.3 (2ϫ CH), 53.8 (CH
) ppm. IR (ATR): ν˜ max = 2849, 2551, Acknowledgments
725, 1611, 1557, 1507, 1436, 1279, 1110, 756 cm .
3
OD): δ = 8.13 (d, J = 8.9 Hz, 2 H), 7.37
–1
13
(
3
1
1
3
–1
1
This work was financially supported by The Fond Unique Inter-
ministériel (REDSUP). We thank F. Albrieux, C. Duchamp, and N.
Henriques (Centre Commun de Spectrométrie de Masse, ICBMS
UMR-5246) for assistance and access to the Mass Spectrometry
facilities.
4
-(Trifluoromethyl)benzyl Alcohol (6b) [349-95-1]: Colorless oil. H
NMR (300 MHz, CDCl
3
): δ = 7.62 (d, J = 8.1 Hz, 2 H), 7.48 (d,
J = 8.1 Hz, 2 H), 4.78 (s, 2 H), 1.75 (br. s, 1 H) ppm. 1 C NMR
3
(
(
(
(
(
8
75 MHz, CDCl
3
): δ = 144.9 (Cq), 129.7 (Cq, J = 32.1 Hz), 127.0
2ϫ CH), 125.5 (2ϫ CH), 124.1 (Cq, J = 218.2 Hz), 64.2
+
·
CH
2
) ppm. GC-MS: t
R
= 5.91 min; m/z (%) = 176 (100) [M ], 145
10) [M+ – CH
·
OH], 127 (76), 107 (100) [M – CF ], 79 (94), 77 [1] J. Seyden-Penne, Reductions by the Alumino- and Borohydrides,
+·
2
3
42). IR (ATR): ν˜ max = 3316, 2929, 1419, 1322, 1100, 1065, 1015,
Wiley-VCH, New York, 1991.
[2] S.-D. Cho, Y.-D. Park, J.-J. Kim, J. R. Falck, Y.-J. Yoon, Bull.
Korean Chem. Soc. 2004, 25, 407–409.
–1
16 cm .
3
-Thiopheneethanol (10b) [13781-67-4]: Yellow oil. 1H NMR
[
3] J. C. S. da Costa, K. C. Pais, E. L. Fernandes, P. S. M. de Ol-
iveira, J. S. Mendonça, M. V. N. de Souza, M. A. Peralta,
T. R. A. Vasconcelos, ARKIVOC (Gainesville, FL, U.S.) 2006,
1, 128–133.
(300 MHz, CDCl
3
): δ = 7.27 (d, J = 4.0 Hz, 1 H), 7.02 (s, 1 H),
6
6
.95 (d, J = 4.0 Hz, 1 H), 3.82 (t, J = 6.4 Hz, 2 H), 2.88 (t, J =
.20 Hz, 2 H), 1.47 (br. s, 1 H) ppm. 13C NMR (75 MHz, CDCl
):
),
3
[
[
[
[
[
[
4] J. Kim, K. A. De Castro, M. Lim, H. Rhee, Tetrahedron 2010,
δ = 139.0 (Cq), 128.4 (CH), 125.6 (CH), 121.5 (CH), 62.6 (CH
2
+
·
66, 3995–4001.
33.5 (CH
1
10 (3), [M+ – H
3329, 2929, 1409, 1044, 1018, 834, 769 cm .
2
) ppm. GC-MS: t
R
= 6.34 min; m/z (%) = 128 (28) [M ],
5] A. R. Jagdale, A. S. Paraskar, A. Sudalai, Synthesis 2009, 660–
·
O], 97 (100) [M+· – CH
2
2
–
OH]. IR (ATR): ν˜ max =
664.
1
6] S. Narasimhan, S. Madhavan, K. Ganeshwar Prasad, Synth.
Commun. 1997, 27, 385–390.
1
2
-Phenylethanol (11b) [60-12-8]: Orange oil. H NMR (300 MHz,
7] L. Pasumansky, D. Haddenham, J. W. Clary, G. B. Fisher, C. T.
Goralski, B. Singaram, J. Org. Chem. 2008, 73, 1898–1905.
8] H. C. Brown, S. Narasimhan, Y. M. Choi, J. Org. Chem. 1982,
CDCl
J = 6.6 Hz, 2 H), 1.45 (br. s, 1 H) ppm. C NMR (75 MHz,
CDCl ): δ = 138.6 (Cq), 129.4 (2ϫ CH), 128.9 (2ϫ CH), 126.8
3
): δ = 7.32–7.22 (m, 5 H), 3.87 (t, J = 6.6 Hz, 2 H), 2.88 (t,
13
3
47, 4702–4708.
(Cq), 64.0 (CH
2
·
), 39.5 (CH
122 (52) [M ], 92 (82), 91 (100) [M – CH
2
) ppm. GC-MS: t
R
= 6.16 min; m/z (%)
OH]. IR (ATR): ν˜ max
9] Y. Pouilloux, F. Autin, J. Barrault, Catal. Today 2000, 63, 87–
+
+·
=
=
2
100.
–1
3329, 3026, 2937, 2875, 1496, 1453, 1043, 745, 697 cm .
[10] P. S. Wehner, B. L. Gustafson, J. Catal. 1992, 135, 420–426.
Eur. J. Org. Chem. 2011, 7400–7406
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
7405

M. Lemaire et al.
FULL PAPER
[
11] Y. Zhou, H. Fu, X. Zheng, R. Li, H. Chen, X. Li, Catal. Com-
mun. 2009, 11, 137–141.
[30] a) K. J. Barr, S. C. Berk, S. L. Buchwald, J. Org. Chem. 1994,
59, 4323–4326; b) M. T. Reding, S. L. Buchwald, J. Org. Chem.
1995, 60, 7884–7890.
[12] J. Zhang, G. Leitus, Y. Ben-David, D. Milstein, Angew. Chem.
[
[
31] S. W. Breeden, N. J. Lawrence, Synlett 1994, 833–835.
2
006, 118, 1131; Angew. Chem. Int. Ed. 2006, 45, 1113–1115–
32] M. D. Drew, N. J. Lawrence, D. Fontaine, L. Sehkri, Synlett
1
133.
1997, 989–991.
[
13] S. Takebayashi, S. H. Bergens, Organometallics 2009, 28, 2349–
[
[
[
[
[
33] a) H. Mimoun, J. Org. Chem. 1999, 64, 2582–2589; b) H. Mim-
oun, Firmenich SA, Switzerland, Patent WO 2001/34110 A1.
34] A. C. Fernandes, R. Fernandes, C. C. Romão, B. Royo, Chem.
Commun. 2005, 213–214.
2351.
[
14] L. A. Saudan, C. M. Saudan, C. Debieux, P. Wyss, Angew.
Chem. 2007, 119, 7617–7620; Angew. Chem. Int. Ed. 2007, 46,
7473–7476.
35] A. C. Fernandes, C. C. Romao, Tetrahedron Lett. 2005, 46,
[
15] W. Kuriyama, Y. Ino, O. Ogata, Takasago International Corpo-
ration, Japan, Patent US 2009-553544 A1.
16] a) G. L. Larson, J. L. Fry, Ionic and organometallic-catalyzed
organosilane reductions, John Wiley & Sons, Inc., Hoboken,
New Jersey 2010, pp. 265–300; b) D. Addis, S. Das, K. Junge,
M. Beller, Angew. Chem. Int. Ed. 2011, 50, 6004–6011; Angew.
Chem. 2011, 123, 6128–6135.
8881–8883.
36] M. Stosur, T. Szymanska-Buzar, J. Mol. Catal. A 2008, 286,
[
98–105.
37] E. Peterson, A. Y. Khalimon, R. Simionescu, L. G. Kuzmina,
J. A. K. Howard, G. I. Nikonov, J. Am. Chem. Soc. 2009, 131,
908–909.
[
38] J. E. Ziegler, G. Du, P. E. Fanwick, M. M. Abu-Omar, Inorg.
Chem. 2009, 48, 11290–11296.
[
[
[
17] K. Homma, H. Takenoshita, T. Mukaiyama, Bull. Chem. Soc.
Jpn. 1990, 63, 1898–1915.
[
39] a) M. Berthod, A. Favre-Réguillon, J. Mohamad, G. Mignani,
G. Docherty, M. Lemaire, Synlett 2007, 1545–1548; b) C. Petit,
A. Favre-Réguillon, B. Albela, L. Bonneviot, G. Mignani, M.
Lemaire, Organometallics 2009, 28, 6379–6382; c) C. Petit, A.
Favre-Réguillon, G. Mignani, M. Lemaire, Green Chem. 2010,
12, 326–330.
18] T. Ohta, M. Kamiya, K. Kusui, T. Michibata, M. Nobutomo,
I. Furukawa, Tetrahedron Lett. 1999, 40, 6963–6966.
19] a) M. Igarashi, R. Mizuno, T. Fuchikami, Tetrahedron Lett.
2
001, 42, 2149–2151; b) K. Matsubara, T. Iura, T. Maki, H.
Nagashima, J. Org. Chem. 2002, 67, 4985–4988.
[
[
[
[
[
[
[
20] Z. Mao, B. T. Gregg, A. R. Cutler, J. Am. Chem. Soc. 1995,
[40] a) S. Laval, W. Dayoub, A. Favre-Reguillon, M. Berthod, P.
Demonchaux, G. Mignani, M. Lemaire, Tetrahedron Lett.
2009, 50, 2092–2094; b) S. Laval, W. Dayoub, L. Pehlivan, E.
Métay, A. Favre-Réguillon, D. Delbrayelle, G. Mignani, M. Le-
maire, Tetrahedron Lett. 2011, 52, 4072–4075.
[41] S. Laval, W. Dayoub, A. Favre-Reguillon, M. Berthod, P. De-
monchaux, G. Mignani, M. Lemaire, Tetrahedron Lett. 2010,
51, 7005–7007.
117, 10139–10140.
21] M. Yato, K. Homma, A. Ishida, Tetrahedron 2001, 57, 5353–
359.
22] S. C. Berk, K. A. Kreutzer, S. L. Buchwald, J. Am. Chem. Soc.
991, 113, 5093–5095.
23] N. Sakai, T. Moriya, T. Konokahara, J. Org. Chem. 2007, 72,
920–5922.
5
1
5
24] A. C. Fernandes, C. C. Romao, J. Mol. Catal. A 2006, 253, 96– [42] a) L. Pehlivan, E. Métay, S. Laval, W. Dayoub, P. Demonchaux,
9
8.
25] S. Das, K. Möller, K. Junge, M. Beller, Chem. Eur. J. 2011, 17,
414–7417.
26] J. Boyer, R. J. P. Corriu, R. Perz, M. Poirier, C. Reye, Synthesis
981, 558–559.
G. Mignani, M. Lemaire, Tetrahedron Lett. 2010, 51, 1939–
1941; b) L. Pehlivan, E. Métay, S. Laval, W. Dayoub, P. De-
monchaux, G. Mignani, M. Lemaire, Tetrahedron 2011, 67,
1971–1976.
7
1
[43] Y. Shi, W. Dayoub, G.-R. Chen, M. Lemaire, Tetrahedron Lett.
2011, 52, 1281–1283.
[44] L. Pehlivan, E. Métay, O. Boyron, P. Demonchaux, G. Mig-
nani, M. Lemaire, Eur. J. Org. Chem. 2011, 4687–4692.
[45] B. H. Lipshutz, Synlett 2009, 509–524.
[27] Y. R. Dumond, A. G. Gum, Molecules 2003, 8, 873–881.
[28] S. C. Berk, S. L. Buchwald, J. Org. Chem. 1993, 58, 3221.
[29] a) X. Verdaguer, S. C. Berk, S. L. Buchwald, J. Am. Chem. Soc.
1
995, 117, 12641–12642; b) X. Verdaguer, M. C. Hansen, S. C.
Berk, S. L. Buchwald, J. Org. Chem. 1997, 62, 8522–8528; c) [46] J. Y. Corey, Chem. Rev. 2011, 111, 863–1071.
M. C. Hansen, X. Verdaguer, S. L. Buchwald, J. Org. Chem. Received: July 12, 2011
1998, 63, 2360–2361.
Published Online: October 26, 2011
7406
www.eurjoc.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2011, 7400–7406