A Versatile Iridium(III) Metallacycle Catalyst for the Effective Hydrosilylation of Carbonyl and Carboxylic Acid Derivatives

Article abstract of DOI:10.1002/ejoc.201700801

A versatile iridium(III) metallacycle catalysed rapidly and selectively the reduction of a large array of challenging esters and carboxylic acids as well as various ketones and aldehydes. The reactions proceeded in high yields at room temperature by hydrosilylation followed by desilylation. Although the reactions of various aldehydes and ketones resulted exclusively in alcohols, the hydrosilylation of esters led to alcohols or ethers, depending on the type of substrate. Regarding the carboxylic acids, again the nature of the reagent controlled the outcome of the hydrosilylation reaction, either alcohols or aldehydes being formed.

Full text of DOI:10.1002/ejoc.201700801

A Journal of
Accepted Article
Title: A versatile iridium(III) metallacycle catalyst for the effective
hydrosilylation of carbonyl and carboxylic acid derivatives
Authors: Christophe Michon, Francine Agbossou-Niedercorn, Xavier
Trivelli, Vincent Rysak, and Yann Corre
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201700801
Link to VoR: http://dx.doi.org/10.1002/ejoc.201700801
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10.1002/ejoc.201700801
European Journal of Organic Chemistry
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A versatile iridium(III) metallacycle catalyst for the effective
hydrosilylation of carbonyl and carboxylic acid derivatives.
Yann Corre,[a,b] Vincent Rysak,[a,b] Xavier Trivelli,[c] Francine Agbossou-Niedercorn*[a,b] and Christophe
Michon*[a,b]
Abstract: A versatile iridium(III) metallacycle catalyses rapidly
and selectively the reduction of a large array of challenging
esters and carboxylic acids as well as various ketones and
aldehydes. Reactions proceed with high yields at room
temperature through hydrosilylation followed by desilylation.
Whether the reaction of various aldehydes and ketones results
exclusively in alcohols, the hydrosilylation of esters leads to
alcohols or ethers depending on the type of substrate.
Regarding the carboxylic acids, the nature of the reagent
controls also the outcome of the hydrosilylation reaction, either
alcohols or aldehydes being formed.
previous studies on hydrosilylation reactions of unsaturated
carbon-carbon and carbon–heteroatom compounds using
iridium(III) metallacycle catalysts,[13] we have recently reported
on the challenging hydrosilylation of amides[13e] and esters.[13d] In
the latter case, the combination of a cationic iridium(III)
metallacycle and 1,3,5-trimethoxybenzene allows the rapid and
selective reduction of esters to aldehydes at room temperature
with high yields through hydrosilylation followed by hydrolysis
(Scheme 1). The ester reduction involves the trapping of
transient silyl cations by the 1,3,5-trimethoxybenzene co-
catalyst, supposedly by formation of an arenium intermediate
whose role was addressed by DFT calculations. Herein, we
report the same accessible iridium(III) metallacycle catalyses
rapidly and selectively the reduction of a large array of
carboxylic acids, esters, ketones and aldehydes with high yields
at room temperature through hydrosilylation followed by
desilylation (Scheme 1).
Introduction
The use of hydrosilanes as reductants is an area of growing
interest for the mild and selective reduction of carboxylic acid
derivatives by using transition metal or Lewis acid catalysts.[1,2]
Indeed, hydrosilylation, which operates without any high
pressure equipment and high temperature, can be an interesting
alternative to hydrogenation, provided that inexpensive and
abundant hydrosilanes are used. Because the reactivity of such
reagents and related reaction intermediates is modular and
depends on the substituents of the silicon atoms, the
hydrosilylation reaction can become a highly chemo- and
regioselective reduction method which tolerates various other
reducible functional groups.[2] However, whereas several
organometallic or organic catalysts were shown to hydrosilylate
aldehydes and ketones,[2-5] the hydrosilylation of less reactive
substrates like hindered ketones,[6] carboxylic acids[7] and
esters[8,9] remains challenging (Scheme 1). Whether several
iridium catalysts were effective for the hydrosilylation of carbonyl
compounds (e.g. aldehydes and ketones)[3] and carbon-carbon
multiple bonds,[10] their applications in the reduction of carboxylic
[12]
acid derivatives[11] and CO2
remain almost unexplored.
Moreover, to the best of our knowledge, only iridium(III) POCOP
(i.e. 2,6-bis(di-tert-butylphosphinito)phenyl) catalyst proved to be
versatile for the effective hydrosilylation of a large array of
carbonyl and carboxylic acid substrates.[3c,11b] Following our
Scheme 1. Hydrosilylation of carboxylic acid derivatives using an iridium(III)
metallacycle.
[a]
Dr. Y. Corre, V. Rysak, Dr. F. Agbossou-Niedercorn, Dr. C. Michon,
Univ. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181 -
UCCS - Unité de Catalyse et Chimie du Solide, F-59000 Lille,
France. E-mail: christophe.michon@ensc-lille.fr,
francine.agbossou@ensc-lille.fr
Results and Discussion
Hydrosilylation of aldehydes
Homepages: http://uccs.univ-lille1.fr/index.php/annuaire/15-fiches-
personnels/221-michon-christophe
http://uccs.univ-lille1.fr/index.php/annuaire/15-fiches-personnels/81-
agbossou-niedercorn-francine
Iridium(III)
metallacycle
pre-catalyst
[Ir],
sodium
tetrakis[(3,5-trifluoromethyl)phenyl]borate
(NaBArF24)
additive and reaction conditions (e.g. silane, solvent,
temperature) initially used for the reduction of esters into
aldehydes (Scheme 1) were applied for the hydrosilylation
of a series of aldehydes (Table 1). The corresponding
alcohols were recovered in excellent isolated yields from
the silylether products through desilylation with
tetrabutylammonium fluoride (TBAF). Catalyst and
[b]
[c]
ENSCL, UCCS-CCM-MOCAH, (Chimie-C7) CS 90108, 59652
Villeneuve d’Ascq Cedex, France
Dr. X. Trivelli, UGSF CNRS, UMR 8576, Université Lille Nord de
France, 59655 Villeneuve d'Ascq Cedex, France.
Supporting information for this article is given via a link at the end of
the document.
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10.1002/ejoc.201700801
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NaBArF24 loadings were decreased to respectively 0.1 and
0.2 mol% as the reactions were still performing well without
any decrease of activity. The hydrosilylation of aromatic
substrates 1a-b was completed with 5 minutes (entries 1,
2). Whether furan 2-carbaldehyde 1c reacted readily (entry
3), the hydrosilylation of thiophene 2-carbaldehyde 1d
required 2 hours to go to completion (entry 4). By
comparison, the more coordinating pyridine analogue 1e
reacted barely in 24 h (entry 5). Hydrosilylation of ortho-
yields after hydrolysis or desilylation with TBAF. At 2
exceptions, catalyst and additive loadings of 0.5 and 1
mol% allowed all reactions to proceed in few hours.
Benzophenone 3a, acetophenone 3b and acetonaphtone
3c were readily reduced in 2 hours (entries 1-3). However,
the hydrosilylation of 2-acetylpyridine 3d proved to be
harder most likely because of a possible catalyst inhibition
through substrate chelation (entry 4). Reactions of other
aromatic and alkyl ketones 3e-h proceeded also well in 2 to
4 hours (entries 5-8). Moreover, the hydrosilylation of more
challenging substrates like sterically hindered ketones[6]
and
para-
substituted
benzaldehydes
1f-i
was
straightforward independently of the substitution pattern of
the substrate (entries 6-9). Finally, alkyl aldehydes 1j-l were
also readily reduced in 5 to 60 minutes (entries 10-12).
was not
a
limitation. Indeed, the reductions of
3i 2-acetylmesitylene 3j and
pivalophenone
,
dicyclohexylmethanone 3h were still straightforward in few
hours (entries 9-11). However, the hydrosilylation of
diisopropylmethanone 3l proved to be harder requiring a
reaction temperature of 40°C and a longer reaction time to
go to completion (entry 12).
Hydrosilylation of ketones
The same catalytic system was subsequently used for the
hydrosilylation of ketones 3a-l (Table 2). The resulting
alcohols 4a-l were retrieved in average to excellent isolated
Table 1. Hydrosilylation of aldehydes 1a-l.
Entry
Aldehyde
Time
(min)
Yield [%][a]
(isolated yield [%])[b]
1
2
5
5
2a 100 (99)
2b 99 (85)
3
15
2c 100 (71)
4
5
120
2d 100 (50)
2e 15 (-)
24 h[c]
6
7
8
9
5
5
5
5
2f 100 (83)
2g 100 (98)
2h 100 (92)
2i 100 (99)
10
11
15
60
2j 99 (83)
2k 100 (75)
12
5
2l 100 (94)
[a] Yield in silyl ether determined by 1H NMR. [b] Isolated yield in alcohols 2a-l after desilylation with TBAF and purification. [c] Temperature = 40 °C.
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Table 2. Hydrosilylation of ketones 3a-l into alcohols 4a-l.
Entry
Ketone
Time
(h)
Yield [%][a]
(isolated yield [%][b]
)
1
2
4a 100 (54)
2
3
2
4b 100 (55)
2
4c 100 (86)
4d 33 (-)
4[c]
10
5
3
4e 100 (99)
6
7
2
2
4
2
2
4f 100 (78)
4g 100 (89)
4h 89 (53)
4i 97 (87)
4j 77 (51)
8
9
10
11
12
3
4k 100 (64)
4l 100 (-)[d]
15
[a] Yield in silylether determined by 1H NMR. [b] Isolated yield in alcohols 4a-l, after hydrolysis or desilylation with TBAF and purification.
[c] Catalyst loading = 1 mol% and temperature = 40 °C. [d] at 40°C because no reaction in 3 hours at 25°C.
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Table 3. Hydrosilylation of esters 5a-p into alcohols 6a-p and ethers 7a-p.
Entry
Ester
Time
(h)
Yield
[%][a]
Selectivity [%][a]
(isolated yield [%])[b]
1
1
100
6a 100 (78)
7a 0 (-)
2
3
1
1
100
100
6b 92
7b 8
6b 73[c]
7b 19[c]
4
1
100
6c 100
7c 0
5
6
3
1
100
100
6d 100 (69)
6d 85 (-)
7d 0 (-)
7d 15 (-)
7
8
1
100
92
6e 89 (68)
6f 100 (68)
7e 11 (-)
7f 0 (-)
24
9
3
1
100
100
6g 79 (54) [d]
6h 99 (94)
7g 21 (-)[d]
7h 1 (-)
10
11
12
15
1
57[e]
6i 100 (38)
6j 100 (81)
7i 0 (-)
7j 0 (-)
100
13
1
100
6k 93 (82)
7k 7 (-)
14
15
1
8
100
100
6l 82 (79)
6m 25(18)
7l 18 (14)
7m 75 (53)
16
17
1
1
100
100
6n 12 (6)
6o 4 (-)
7n 88 (46)
7o 96 (92)
18
1
100
6p 60 (33)
7p 40 (22)
[a] Yield determined by 1H NMR. [b] Isolated yields in alcohols 6a-p or ethers 7a-p after desilylation with TBAF and purification. [c] for 2 eq. Et3SiH
with benzaldehyde (8%) as a side product. [d] Same ratio alcohol / ether at t = 6 hours. [e] Temperature = 60 °C and solvent = TCE.
Hydrosilylation of esters
substrate. Similarly to aldehydes and some ketones, the
alcohol products were obtained through desilylation of the
related silylethers with tetrabutylammonium fluoride (TBAF).
We noticed the use of 3 equivalents of triethylsilane (entries
2, 3) or of a longer reaction time (entries 5, 6) could
enhance the reaction selectivity for alcohols by reducing
significantly the amount of formed alkyl ethers. Brookhart et
al. previously reported iridium(III) POCOP catalyst could
cleave alkyl ethers into silylated alcohols and alkanes using
triethylsilane.[14]
Next, the same catalytic system was applied for the
hydrosilylation of esters (Table 3). Though these reductions
were known to be more difficult,[8,9] most of the reactions
proceeded well with iridium(III) metallacycle pre-catalyst [Ir]
and NaBArF24 additive loadings respectively of 1 and 2
mol%. Alcohols 6a-p and/or alkyl ethers 7a-p were obtained
with variable selectivities and moderate to high isolated
yields depending on the molecular structure of the
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Table 4. Hydrosilylation of carboxylic acids 8a-p into alcohols 9a-p or aldehydes 10a-p.
Yield [%][a]
(isolated yield [%])[b]
Entry
Carboxylic acid
t (h)
T (°C)
1
15
40
9a 100 (67)
2
3
5
25
40
9b 100 (90)
9c 100 (68)
15
4
5
5
25
25
9d 100 (83)
9d 16 (-)
5[c]
6
7
15
15
25
25
9e 100 (84)
9f 100 (77)
8
9
5
25
40
10g 100 (83)
10h 100 (88)
15
10
11
12
13
14
15
16
15
15
15
15
15
15
40
40
40
40
40
40
40
40
10i 100 (83)
10j 100 (79)
10k 100 (79)
10l 100 (81)
9m 36 (26)
9n 100 (93)
9o 100 (74)
17
18
15
24
40
40
9p 100 (60)
0[d]
[a] Yield measured by 1H NMR. [b] Isolated yields in alcohols 9a-f and 9m-p or aldehydes 10g-l after hydrolysis and purification.
[c] with 4 eq. Et3SiH. [d] Same result in 24 hours at 80°C in TCE.
According the present results, iridium(III) metallacycles
catalysed a similar ether cleavage depending on the
substrate basicity. Although aromatic ethers 7b and 7d
were converted to alcohols 6b and 6d (entries 2,3,5,6),
alkyl ethers 7m and 7o remained unreacted (entries 15,17).
The reaction of benzoate derivatives 5a-c led to benzyl
alcohol independently of the nature of the R2 substituent
(entries 1-4). Hydrosilylation of ortho- and para- substituted
benzoates 5d-e and 5g-h was straightforward to the related
alcohols as the main products independently of the
substitution pattern of the reagent (entries 5-7,9-10).
However, the para- substitution by an ethoxy group led to a
less reactive substrate 5f which was fully reduced in 24
hours (entry 8).
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Similarly, the hydrosilylation of thiophene derivative 5i
proved to be difficult, a reaction of 15 hours being required
to obtain the related alcohol in an average yield (entry 11).
Interestingly, the reaction of lactone 5j led effectively to the
related diol (entry 12). Whether the hydrosilylation of
cyclohexyl and benzyl ethyl esters 5k-l afforded alcohols as
the major products (entries 13-14), the reaction of other
alkyl substrates 5m-o resulted predominantly in the related
ethyl ethers (entries 15-17), probably due to their longer
alkyl chains and their less sterically hindered structures.
Finally, the hydrosilylation of methyllinoleate 5p was far less
selective resulting in the corresponding alcohol along with
significant amount of the methyl ether product (entry 18).
proved to be critical to allow the hydrosilylation to proceed
(entries 4,5). We noticed also an increase of the reaction
temperature to 40°C was often required to recover products in
high yields. Hydrolysis of the resulting silyl ethers or acetals to
the corresponding alcohols or aldehydes could be performed by
simple addition of water to the reaction mixture. Indeed,
hydration of the remaining 0.5 mol% of NaBArF24 resulted in a
catalysis producing
a Brønsted acid, which could cleave
chemoselectively the generated silyl acetals.[13d,15] On the whole,
we obtained selectively alcohols 9a-f,m-p or aldehydes 10g-l in
good to high isolated yields depending on the molecular
structure of the substrate. The hydrosilylation of benzoic acid 8a
and 2-thiophene acetic acid 8c required 15 hours of reaction at
40°C to afford the related alcohols (entries 1, 3). By comparison,
the reaction of phenylacetic acid 8b and 3-phenylpropionic acid
8d were faster, alcohols 9b and 9d being obtained in only 5
hours at 25°C (entries 2, 4). However, alkyl substrates 8e and 8f
needed 15 hours to lead to the corresponding alcohols (entries
6, 7). To our surprise, the hydrosilylation of 2-phenylpropanoic
acid 8g and diphenylacetic acid 8h afforded aldehydes 10g-h
(entries 8, 9). Whether a similar trend was observed for
halogenated benzoic acids 8i-l (entries 10-13),
Hydrosilylation of carboxylic acids
Since the catalytic system was found to be effective in the
hydrosilylation of esters, we subsequently studied the more
challenging reduction of carboxylic acids (Table 4).[7] Whether
iridium(III) metallacycle pre-catalyst and NaBArF24 additive
loadings were reduced to respectively 0.5 and 1 mol%, the
change of triethysilane for 1,1,3,3-tetramethyldisiloxane (TMDS)
Scheme 2. Reaction mechanism proposal.
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the reaction of other electron poor substrates like para-
nitrobenzoic acid 8m and 2-bromo-2-phenylacetic acid 8p led to
alcohols 9m and 9p (entries 14, 17). If the hydrosilylation of
para-methoxybenzoic acid 8n was rather straightforward to the
alcohol 9n (entry 15), ortho-methoxybenzoic acid 8o was far
less reactive probably due to its chelation to the catalyst (entry
16). Such inhibition effect was confirmed by the unreactivity of
the Supporting Information). At this stage, further investigations
on the reaction mechanism proved to be difficult.
Conclusions
To summarise, we have shown a versatile iridium(III)
metallacycle catalyses effectively the reduction of various
carbonyl and carboxylic acid derivatives with high yields at
room temperature through hydrosilylation followed by
desilylation or hydrolysis. The reaction of aldehydes and
ketones, including sterically hindered substrates, results
exclusively in alcohols. The hydrosilylation of more
challenging compounds like carboxylic acid derivatives
proceeds also well. Esters lead rapidly to either alcohols or
ethers depending on the substrate basicity. Similarly, the
nature of the carboxylic acid reagents controls also the
outcome of the hydrosilylation reaction, either alcohols or
aldehydes being formed. According our present and past
works, the reactivity of iridium(III) metallacycles is promising
in catalytic hydrosilylations of organic compounds.
pyridine-2-carboxylic acid 8q,
a
stronger chelate which
prevented any reaction to occur (entry 18).
Reaction mechanism
Regarding the reaction mechanism, an ionic hydrosilylation[14,16]
pathway could be presumed. Djukic et al. have already shown
through a combination of organometallic syntheses and DFT
calculations
a
cohesive
hydridoiridium(III)→silylium
donor−acceptor complex could exist.[17] Hence, we assumed our
reaction pathway could differentiate from the others involving
iridium catalysts[2,16] by the activation mode of the silane. At first,
precatalyst is dehalogenated by NaBArF24 to give a transient
cationic complex A (Scheme 2) which was observed by ESI-MS
while analysing a reaction crude mixture (Figure S1 in the
Supporting Information).[13a,e] The iridium catalyst activates the
silane reagent through the formation of a silane–iridium adduct
B.[16,17] Such an activation process would produce an iridium
hydride complex C[18] and a silyl cation.[19] The latter may
activate the carbonyl group of the substrate and generate a
silyloxy carbonium species D, which can be stabilised by the
electron-donating group R’. Reaction with a first equivalent of
the iridium hydride complex affords silyl intermediate E along
with the cationic iridium catalytic species A. At that stage,
several pathways are possible depending on the nature of the
substrate. In the case of aldehydes and ketones, a further
hydrolysis or desilylation of silyl ether E offers the alcohol
product. Concerning the hydrosilylation of carboxylic acids 8a-p
or esters 5a-p, the silyl intermediate E can react further through
activation of its ether or hydroxy groups by silyl cation and
formation of intermediates F. After reaction with a second
equivalent of iridium hydride complex C, alkylether, silylether or
acetal products are either formed along with the release of the
catalytic cationic iridium species A and a final hydrolysis or
desilylation step affords the organic product as an alcohol, ether
or aldehyde.
Experimental Section
General Procedure for the catalysis
In a Schlenk tube, the reagent (0.15 mmol, 1 eq.) and
iridium (III) catalyst (0.1-1 mol%) are introduced. NaBArF24
salt (0.2-2 mol%) is then added in a glovebox. Under
nitrogen, dichloromethane (2 mL, dry) and the silane
reagent (0.18 mmol, 1.2-3.0 eq.) are subsequently added
by syringe and the reaction mixture is heated at 25°C under
stirring for a defined time (the Schlenk tube being closed
under N2). In order to follow the advancement of the
reaction, aliquots (0.1 mL) were taken at defined times.
They were filtered over Celite and washed with
dichloromethane (3 mL) before being analysed by GC.
1
Alternatively, H NMR analyses could be performed on the
samples after their evaporation under vacuum. At the end
of the hydrosilylation reaction, the crude reaction mixture is
hydrolysed or desilylated following method A, B, C or D.
Afterwards, the resulting solution is extracted with
diethylether and washed with brine. Organic phases are
then dried over MgSO4 and evaporated under vacuum. The
resulting solid or oily residue is then purified by flash
chromatography or preparative TLC.
Method A (for ketones 3f, 3k): After filtration of the crude
mixture over a pad of silica subsequently washed with
dichloromethane, solvents are evaporated under vacuum.
The resulting crude mixture is then dissolved in methanol
and an aqueous solution of acid chloride (1M, 1.5 mL) is
added. The resulting solution is vigorously stirred during 12
hours at room temperature. In some cases, a reaction time
of 24 to 48 hours is necessary to recover products in high
yields.
Method B (for ketones 3a, 3e, 3h, 3i, 3j): After filtration of
the crude mixture over a pad of silica subsequently washed
with dichloromethane, solvents are evaporated under
vacuum. The resulting crude mixture is then dissolved in
methanol and an aqueous solution of sodium hydroxide
(3M, 1.3 mL) is added. The resulting solution is vigorously
stirred during 12 hours at room temperature. In some
cases, a reaction time of 24 to 48 hours is necessary to
recover products in high yields.
Concerning the hydrosilylation of esters 5a-p, alcohols 6a-
p and/or ethers 7a-p are obtained depending on the nature of
the substrates and their steric hindrance. Although aromatic and
sterically hindered esters are mainly reduced to alcohols, linear
alkyl esters are converted to ethers. Moreover, iridium(III)
metallacycle catalyst can cleave alkyl ether[14] into silylated
alcohols and alkanes depending on the substrate basicity.
Although aromatic ethers 7b and 7d were converted to alcohol
6b and 6d, alkyl ethers 7m and 7o remained unreacted.
Regarding the hydrosilylation of carboxylic acids, alcohols
9a-f,m-p or aldehydes 10g-l are obtained selectively after a
subsequent hydrolysis, without any defined influence of the
substrates, that is to say the effect of the steric and electronic
parameters of the carboxylic acids (Table 4). As opposed to the
use of Lewis acid catalysts like tris(pentafluorophenyl)borane7d
or Gallium trichloride,7g the emission of hydrogen gas was not
observed along our iridium catalysed reactions. The use of 2
equivalents of 1,1,3,3-tetramethyldisiloxane (TMDS) does not
always allow the formation of a single acetal. If the reaction
selectivity depends on the molecular structure of the starting
substrate, a rationalisation based on electronic or steric effects
was not possible (Scheme 2, Schemes S1-S3, Figures S2-S5 in
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Method C (for aldehydes and esters, for ketone 3b, 3c,
3g): After filtration of the crude mixture over a pad of silica
subsequently washed with dichloromethane, solvents are
evaporated under vacuum. The resulting crude mixture is
then dissolved in distilled THF (5 mL) under nitrogen and
one equivalent of tetrabutylammonium fluoride (TBAF, THF,
1M) is added at room temperature. The resulting solution is
vigorously stirred during 12 hours at room temperature. In
some cases, a reaction time of 24 to 48 hours is necessary
to recover products in high yields.
Method D (for carboxylic acids): After full-conversion,
100 µL of water (1440 eq.) are added to the crude reaction
mixture in dichloromethane and the resulting solution is
vigorously stirred during 1 hour at room temperature. In
some cases, a reaction time of 4 hours is necessary to
recover products in high yields.
Shinohara, H. Nakamura, H. Teramoto, S. Sakaguchi, J. Mol. Cat. A:
Chem. 2016, 421, 138-145.
[4]
[5]
Hydrosilylation of aldehydes and ketones using coinage metals (Cu, Au,
Ag): a) S. Díez-González, S. P. Nolan, Acc. Chem. Res. 2009, 41, 349-
358; b) B. H. Lipshutz, Synlett 2009, 509–524; c) S. R. Roy, S. C. Sau,
S. K. Mandal, J. Org. Chem. 2014, 79, 9150-9160; d) E.
Vasilikogiannaki, I. Titilas, C. Gryparis, A. Louka, I. N. Lykakis, M.
Stratakis, Tetrahedron 2014, 70, 6106-6113; e) M. Teci, N. Lentz, E.
Brenner, D. Matt, L. Toupet, Dalton Trans. 2015, 44, 13991-13998.
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Acknowledgements
The University of Lille 1 and Région Hauts-de-France are
acknowledged for PhD fellowships (Y. C; V.R.). The CNRS, the
Chevreul Institute (FR 2638), the Ministère de l’Enseignement
Supérieur et de la Recherche, the Région Hauts-de-France and
the FEDER are acknowledged for supporting and funding
partially this work. Mrs Céline Delabre (UCCS) is thanked for GC
and GC-MS analyses. Mrs Nathalie Duhal, Mrs Céline Lenglart
and Dr Mostafa Kouach (Univ. of Lille) are thanked for HRMS
analyses.
Keywords: hydrosilylation; iridium; metallacycle; carbonyl
derivatives; carboxylic acid derivatives.
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10.1002/ejoc.201700801
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FULL PAPER
Hydrosilylation of carboxylic acid and carbonyl derivatives.
FULL PAPER
Hydrosilylation.
A
versatile
Yann Corre, Vincent Rysak, Xavier
Trivelli, Francine Agbossou-Niedercorn,*
Christophe Michon*
iridium(III) metallacycle catalyses
rapidly and selectively the reduction of
a large array of challenging esters and
carboxylic acids as well as various
ketones and aldehydes. Reactions
proceed with high yields at room
temperature through hydrosilylation
followed by desilylation. The reaction
of esters leads to alcohols or ethers
depending on the type of substrate.
Regarding carboxylic acids, the nature
of the reagent controls also the
Page No. – Page No.
A versatile iridium(III) metallacycle
catalyst for the effective
hydrosilylation of carbonyl and
carboxylic acid derivatives .
outcome
of
the
hydrosilylation
reaction, either alcohols or aldehydes
being formed.
This article is protected by copyright. All rights reserved.