Cyclopentadienone iron tricarbonyl complexes-catalyzed hydrogen transfer in water

Article abstract of DOI:10.3390/molecules25020421

The development of efficient and low-cost catalytic systems is important for the replacement of robust noble metal complexes. The synthesis and application of a stable, phosphine-free, water-soluble cyclopentadienone iron tricarbonyl complex in the reduction of polarized double bonds in pure water is reported. In the presence of cationic bifunctional iron complexes, a variety of alcohols and amines were prepared in good yields under mild reaction conditions.

Full text of DOI:10.3390/molecules25020421

molecules
Communication
Cyclopentadienone Iron Tricarbonyl
Complexes-Catalyzed Hydrogen Transfer in Water
Daouda Ndiaye 1,2, Sébastien Coufourier 1 , Mbaye Diagne Mbaye 2, Sylvain Gaillard 1 and
Jean-Luc Renaud 1,
*
1
Normandie Univ., LCMT, ENSICAEN, UNICAEN, CNRS, 6 boulevard du Maréchal Juin,
14050 Caen, France; daouda.ndiaye79@gmail.com (D.N.); coufourier.sebastien@gmail.com (S.C.);
sylvain.gaillard@ensicaen.fr (S.G.)
Université Assane Seck de Ziguinchor, BP 523, Ziguinchor, Senegal; mmbaye@univ-zig.sn
Correspondence: jean-luc.renaud@ensicaen.fr; Tel.: +33-231-452842
2
*
ꢀꢁꢂꢀꢃꢄꢅꢆꢇ
Academic Editor: Hans-Joachim Knölker
Received: 30 December 2019; Accepted: 17 January 2020; Published: 20 January 2020
ꢀꢁꢂꢃꢄꢅꢆ
Abstract: The development of efficient and low-cost catalytic systems is important for the replacement
of robust noble metal complexes. The synthesis and application of a stable, phosphine-free,
water-soluble cyclopentadienone iron tricarbonyl complex in the reduction of polarized double
bonds in pure water is reported. In the presence of cationic bifunctional iron complexes, a variety of
alcohols and amines were prepared in good yields under mild reaction conditions.
Keywords: iron complexes; hydrogen transfer; reductive amination; alcohols; amines
1. Introduction
The reduction of polarized C=X bonds is an important process, both in industry and in academia,
for the synthesis of fine chemicals, perfumes, agrochemicals, and pharmaceuticals [
use of stoichiometric amounts of borohydrides or aluminium hydrides, metal-catalyzed pathways
to amines and alcohols have been introduced [ 14]. These procedures consist of hydrogenation,
hydrosilylation, and transfer hydrogenation (with iso-propanol or formic acid) and involve mainly
platinum complexes [ 10], but recent contributions highlighted the rise of Earth-abundant metals
for such reductions [11 14]. Hydrogenation is the most atom economical approach, but requires
1–8]. To avoid the
9
–
9
,
–
hydrogen gas handling and consequently implies some safety issues. Hydrogen transfer (TH) is an
alternative pathway and a more practical tool. Alcohols and formic acid (or formates) are among the
most advantageous hydride donors.
Water is a non-toxic, non-flammable, non-explosive and also an economically relevant
solvent [15
the environmentally acceptable process, the simple product separation and, in some reactions, the
possibility to control the selectivity by adjusting the pH [15 16]. Despite these advantages, the use of
water in catalysis, and more specifically, in reduction, still constitutes a challenge and is underexplored
compared to organic solvent [17 18]. Hydrogenation of ketones and imines [19], and reductive
,16]. Water-soluble organometallic complexes have attracted some interest because of
,
,
amination [20] in water have been reported with few iron complexes. As an example; our group has
disclosed the first water-soluble and well-defined cyclopentadienone iron complex able to catalyze the
reduction of aldehydes, ketones, and 2-substituted dihydroisoquinolines in pure water at 85–100 ◦C
under hydrogen pressure (Figure 1, for the first synthesis of a water-soluble cyclopentadienone iron
complex, see [19]). Little is known on the transfer hydrogenation with Earth-abundant complexes,
while formates are used by enzymes for enantioselective reduction. To the best of our knowledge,
excepted the hydrogen transfer reduction of heterocyclic compounds with formic acid catalyzed by
a cobalt-phosphines complex [20], no reduction of polarized C=X bonds (aldehydes, ketones, and
Molecules 2020, 25, 421; doi:10.3390/molecules25020421
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Molecules 2020, 25, 421
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imines) with formic acid derivatives has been yet reported. Toward this objective, we thought of
developing new water-soluble non-phosphine ligand iron complexes for the reduction of polarized
bonds in the presence of formates or formic acid in pure water.
Figure 1. Previous water-soluble cyclopentadienone iron complex and new complexes for
application reduction.
In 2015, we introduced in catalysis the tricarbonyl iron complex Fe2 bearing a
diaminocyclopentadienone ligand [21]. Compared to other cyclopentadienone iron carbonyl complexes,
this phosphine-free iron complex has, to the best of our knowledge, the highest catalytic activities to
date in reductive amination [21], in chemoselective reduction of
hydrogenation of carbon dioxide [23], in alkylation of ketones [24
indoles [25 30] and alcohols [31 32]. In our ongoing interest in reduction and alkylation, we thought that
α
,
β-unsaturated ketones [22], in the
–
27], amines [25 28], oxindoles [29],
,
,
,
a water-soluble analog of Fe2 would be more active than our previous water-soluble cyclopentadienone
iron complex Fe3 (Figure 1). In this work, we report on the synthesis and application of two
water-soluble cyclopentadienone iron complexes in the reduction of aldehydes and in reductive
amination in pure water.
2. Results and Discussion
2.1. Synthesis of Complexes
To develop water-soluble iron complexes, we selected a diaminocyclopentadienone ligand bearing
ammonium functionalities [33]. The tetraamines
2 and 4 were prepared from diethyloxalate and
N,N-dimethylpropylenediamine and N-aminopropylenemorpholine via an amidation followed by a
reduction in good overall yield (93 and 95%, respectively). The corresponding aminocyclopentadienone
ligands
1 and 2 were then prepared by reacting the amines 2 and 4 with the cyclopentatrienone in
refluxing methanol for 16 h and were isolated in moderate yield (62% and 88%, respectively, Scheme 1).
The complexes Fe6 and Fe7 were synthesized in 48% and 76% yield by simple heating of the
corresponding amino ligand with [Fe2(CO)9] in refluxing toluene (Scheme 1). Finally, the water-soluble
bifunctional iron complexes Fe4 and Fe5 bearing ionic frameworks were obtained in almost quantitative
yields after a subsequent alkylation of the pendant amines with iodomethane (Scheme 1) [33]. These
1
complexes were fully characterized by H-, 13C-NMR, and IR spectroscopies (see Supplementary
Materials). These analyses showed that complexes Fe2 and Fe4-Fe7 have similar features. The back
donation from the metal center to the CO ligands is more significant than in the Knölker’s complex
Fe1 [34,
35]. Thus, the CO stretching frequencies were at 2032, 1961, and 1919 cm−1 and at 2015 and
1967 cm−1 in the neutral complexes Fe6 and Fe7, respectively, at 2038 and 1955 cm−1 and at 2034 and
1957 cm−1 in the ionic complexes Fe4 and Fe5, respectively. These frequencies are comparable to those

Molecules 2020, 25, 421
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of the analog Fe2 (2027, 1962 and 1947 cm−1) and lower than those of the Knölker’s complex Fe1 (2061,
2053, and 1987 cm−1) or its water-soluble analog Fe3 (2066, 2016, and 1996 cm−1) [19].
Ph
HO
O
Me2N
Me2N
3
3
Ph
Ph
O
3
Ph
H
N
N
Ph
3
N
Fe2(CO)9 (2 equiv.)
N
NMe2
3
Me2N
N
O
O
CH3OH
H
toluene
reflux, 16 h
N
Ph
reflux, 16 h
3
Me2N
OC
Me2N
Fe
CO
CO
1, 62 %
Fe6, 48 %
3
I
Me2N
Me3N
Ph
Ph
CH3I (3 equiv.)
N
N
O
O
dichloromethane
r.t., 16 h
N
N
I
Ph
Ph
Me2N
Me3N
Fe
Fe
CO
CO
CO
OC
OC
CO
Fe6
Fe4, 98 %
Ph
HO
O
O
N
O
N
3
3
Ph
Ph
O
3
N
O
Ph
N
H
Ph
Fe2(CO)9 (2 equiv.)
3
N
N
3
O
O
N
N
N
CH3OH
reflux, 16 h
toluene
reflux, 16 h
H
Ph
N
O
3
N
O
N
Fe
CO
CO
OC
O
2, 88 %
4
Fe7. 76 %
O
I
O
N
N
3
3
N
Ph
Ph
O
N
CH3I (3 equiv.)
O
N
N
dichloromethane
r.t., 16 h
Ph
Ph
I
3
3
N
N
O
O
Fe
Fe
CO
CO
CO
CO
OC
OC
Fe5. quant.
Fe7
Scheme 1. Synthesis of the iron complexes Fe4, Fe5, Fe6, and Fe7.
2.2. Iron-Catalyzed Reduction of Carbonyl Compounds
With these complexes in hands, we evaluated their catalytic activities in the reduction of
4-methoxybenzaldehyde as a benchmark reaction. Various methods of activation can be used with
the cyclopentadienone iron carbonyl complexes [34–44]. We applied in this work the activation with
Me3NO as oxidant [34
–
42]. Our first attempt with formic acid, in the presence of 2 mol % of Fe4
◦
and 2.5 mol % of Me3NO at 100 C for 24 h in 2 mL of pure water (concentration of 0.5 M), was
unsuccessful as no reduction was noticed (entry 1, Table 1). In sharp contrast, in the same reaction
conditions, complete conversions were obtained with different formate salts (entries 2–5, Table 1).
Without a hydride donor or iron complex, no reduction occurred (entries 6–7, Table 1). Decreasing
the reaction time (entries 8 and 11, Table 1), the catalyst loading (entry 13) and the amount of formate
(entry 14) led to a drop in the conversion. No variation of the conversion was noticed by lowering the
temperature to 80 ◦C (entries 3 and 9, Table 1), while, at 60 ◦C, the conversion was only 75% (entry

Molecules 2020, 25, 421
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12). To our surprise, the first generation water-soluble cyclopentadienone iron complex Fe3 did not
catalyze the reduction of 4-methoxybenzaldehyde in these conditions, while Fe5 appeared as active as
Fe4 (entries 10–15, Table 1). Finally, the best conditions for the reduction of 4-methoxybenzaldehyde
into the corresponding alcohol 4a were: 1 mmol of aldehyde, in the presence of five equivalents of
sodium formate in 2 mL of water, 2 mol % of Fe4 or Fe5 and 2.5 mol % of Me3NO at 80 ◦C for 24 h.
Table 1. Optimization of the reaction conditions for the aldehyde reduction a.
HCO2X, Fe (2 mol%)
Me3NO (2.5 mol%)
OH
O
H2O, T (°C), t (h)
MeO
MeO
Temperature
Conv. (%) b
Entry
HCO2X
Fe
Time (h)
(◦C)
100
100
1
2
HCO2H
HCO2H/Et3N
(1/1)
Fe4
Fe4
24
24
0
100
3
4
5
6
7
HCO2Na
HCO2K
HCO2Cs
-
HCO2Na
HCO2Na
HCO2Na
HCO2Na
HCO2Na
HCO2Na
HCO2Na
HCO2Na
HCO2Na
Fe4
Fe4
Fe4
Fe4
-
Fe4
Fe4
Fe3
Fe4
Fe4
Fe4
Fe4
Fe5
100
100
100
100
100
100
80
80
80
60
80
24
24
24
24
24
16
24
24
16
24
24
24
24
100
100
100
0
0
83
8
9
100 (99%) c
10
11
12
13 d
14 e
15
0
81
75
53
86
80
80
100 (98%) c
a
General conditions: HCO2X (5 mmol, 5 equiv.), 4-methoxybenzaldehyde (1 mmol), pre-catalyst (2 mol %), Me3NO
(2.5 mol %), water (2 mL). b Conversion was determined by 1H-NMR spectroscopy analysis. Isolated yield in the
bracket. Fe 0(1 mol %), Me3NO (1.25 mol %) were used. HCO2Na (3 mmol, three equiv.) were used.
c
d
e
Having established the optimized conditions, we delineated the scope of the carbonyl derivatives
(Table 2). Both electron-donating (methoxy, methyl, acetal substituents) and electron-withdrawing
(nitro, nitrile, and ester substituents) groups were tolerated in this reduction. The corresponding
alcohols 4a
–
m
were isolated in excellent yields in all examples (91–99%, Table 2). No reduction
) was observed. Other
of halogen-carbon bonds in the substituted phenyl group (compounds 4i
–
j
reducible functions, such as ester or nitrile, were preserved in these conditions. Heteroaromatic
derivatives, such as pyridine or thiophene carboxaldehyde, furfural, did not impede the catalytic
activity and provided the alcohols 4n
aldehydes were also engaged in this reduction and the corresponding alcohols 4s
–
r
in 75–98%yield (Table 2). Finally, to extend the scope, aliphatic
were isolated in
–v
92–99% yield (Table 2). It is worth to mention that (i) ethanol was used as a co-solvent with some
substrates to facilitate the solubility and consequently enhanced the reactivity; and (ii) no reaction
occurred in a mixture of water and ethanol without sodium formate.

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Table 2. Iron-catalyzed reduction of aldehydes with sodium formate a.
HCO2Na (5 equiv.)
Fe4 (2 mol%)
Me3NO (2.5 mol%)
(Het)Aryl, Alkyl
(Het)Aryl, Alkyl
OH
O
H2O, 80 °C, 24 h
OCH3
OH
H3CO
O
O
OH
OH
OH
OH
H3CO
4a, 99 %
4b, 98 %
4c, 91 %
4d, 97 %b
4e, 95 %b
X
H3CO
OH
OH
OH
OH
OH
H3CO
OCH3
O2N
4g, 96 %b
4h, 99 %b
4i, X = Br, 75 %
4j, X = Cl, 92 %
4k, 96 %
4f, 99 %b
OH
OH
OH
OH
OH
N
N
NC
N
MeO2C
4l, 98 %
4n, 82 %
4o, 75 %
4p, 91 %
4m, 96 %
Y
OH
OH
OH
OH
OH
OH
4t, 99 %b
4q, Y = O, 98 %
4r, Y = S, 91 %
4s, 99 %b
4u, 98 %b
4v, 92 %b
a
General conditions: aldehyde (1 mmol), HCO2Na (5 mmol, 5 equiv.), pre-catalyst Fe4 (2 mol %), Me3NO (2.5 mol
%), water (2 mL). b H2O/EtOH 1/1.
2.3. Iron-Catalyzed Reductive Amination
Having established a simple protocol for the reduction of aldehydes in water, we thought to
extend this work to the synthesis of amines. Amines are usually prepared via the reduction of C=N
bonds either in catalytic conditions under hydrogen pressure or in stoichiometric conditions in the
presence of aluminum/boron hydride [45]. However, imines are not always easily prepared and cannot
be stable. Reductive amination of aldehydes constitutes a direct route to amines, without requiring any
purification of the imine intermediate. Many efforts have been devoted to the development of reductive
amination [46–48]. For example, in iron chemistry, Bhanage described that a combination of iron sulfate
and ethylenediaminetetraacetic acid (EDTA) catalyzed a reductive amination under hydrogen pressure
(400 psi) in water at elevated temperatures (150 ◦C) [20]. Beller reported a reductive amination with
anilines catalyzed by Fe2(CO)9 under high hydrogen pressure and elevate temperature [49]. We have
reported that cyclopentadienone iron tricarbonyl complexes [21,34,35] or cyclopentadienyl iron(II)
tricarbonyl complex [50] were able to catalyzed the reductive alkylation of various amines and carbonyl
derivatives under 5 bar of hydrogen, at 40–70 ◦C and even room temperature. To avoid the use of a
large amount of hydride (and the concomitant formation of wastes) or the handling of gas, hydrogen
transfer with formate derivatives appears as a simple and versatile procedure. The reductive alkylation
of N-methylbenzylamine with citronellal was chosen as a model reaction for the optimization of the
reaction conditions. Three formate salts were tested, and the cation appeared to be crucial for the
catalytic activity (entries 1–4, Table 3). Indeed, the ammonium favored both the condensation and the

Molecules 2020, 25, 421
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reduction (via the formation of an iminium intermediate). Fe4 and Fe5 provided the alkylated amines
with the same conversion and selectivities (entries 1–2, Table 3). Both water-soluble complexes Fe4 and
Fe5 could then be used in this reaction (as it was also mentioned in the reduction of aldehydes), but for
the rest of the study, we will use Fe5 as pre-catalyst as the overall conversion in reductive amination is
somewhat higher. Without a hydride donor, no reduction occurred (entries 5, Table 3), and only the
imine was obtained. Decreasing the temperature was detrimental to the catalytic activity as a drop
of the conversion in amine was noticed (entries 6–8, Table 3). Finally, an increase of the amount of
ammonium formate to 6.5 equivalent furnished the alkylated amine in 70% isolated yield (entry 9,
Table 3).
Table 3. Optimization of the reaction conditions for the reductive amination a.
HCO2X, [Fe], Me3NO
N
Ph
N
Ph
O
N
Ph
+
+
H
H2O, T(°C), 24 h
5a
5a'
Selectivity
Conv. (%) b
Entry
HCO2X (equiv.)
[Fe]
T (◦C)
(5a)/(5a’) b
1
2
3
4
5
6
7
8
9
HCO2NH4 (5)
HCO2NH4 (5)
HCO2K (5)
HCO2Cs (5)
-
HCO2NH4 (5)
HCO2NH4 (5)
HCO2NH4 (5)
HCO2NH4 (6.5)
Fe4
Fe5
Fe5
Fe5
Fe5
Fe5
Fe5
Fe5
Fe5
90
90
90
90
90
85
80
40
90
93
95
94
93
100
91
83
80
96
77/23
77/23
60/40
40/60
0/100
67/33
69/31
52.5/47.5
91/9 (70) c
a
General conditions: HCO2X (5 mmol, 5 equiv.), citronellal (1 mmol), N-methylbenzylamine (2 equiv.), pre-catalyst
Fe (2 mol %), Me3NO (2.5 mol %), water (2 mL). Conversion and selectivity were determined by 1H-NMR
spectroscopy analysis. Isolated yield in the bracket.
b
c
With the optimized conditions in hands, we evaluated some aliphatic and benzylic amines with
aromatic and aliphatic aldehydes (Table 4). Whatever the benzylic amine used with citronellal, the
isolated yield was good (5a
from the 2-phenylethylamine (Table 4). Amines 5d
benzaldehydes. First, as observed previously, no reduction of halogen-carbon bonds in the substituted
phenyl group was observed, and the corresponding alkylated amines 5f were obtained in around 50%
–b, 61–70%), while the alkylated amine 5c was obtained in a low yield (21%)
–
k
were prepared in 11–64% yield from various
–h
yield. The reductive alkylation of N-methylbenzylamine with thiophene carboxaldehyde furnished
the corresponding amine in a 64% yield. The reductive amination with electron-rich benzaldehyde
and N-methylbenzylamine led to the alkylated amine 5j in very modest yields (13%, Table 4).

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Table 4. Iron-catalyzed reductive amination with ammonium formate a.
HCO2NH4 (6.5 equiv.)
Fe4 or Fe5 (2 mol%), Me3NO (2.5 mol%)
R3
R2 R3
N
R1
N
R1
+
O
R2
H
H2O, 90 °C, 24-48 h
(2 equiv.)
5
N
N
N
N
H
S
5d, 64 %b
5a, 70 %
5b, 61 %
5c, 21 %
R = H, 5e, 53 %b
R = F, 5f, 51 %b
R = Br, 5g, 52 %
R = Cl, 5h, 53 %
R = CH3, 5i, 53 %
O
O
N
N
R
5j, 13 %
a
General conditions: aldehyde (1 mmol), amine (2 equiv.), HCO2NH4 (6.5 mmol, 6.5 equiv.), pre-catalyst Fe4 or Fe5
(2 mol %), Me3NO (2.5 mol %), water (2 mL), 90 ◦C for 24 h. for 48 h.
b
2.4. Recycling of the Water-Soluble Iron Complex
One of the main goals, when reactions are carried out in the water, is the study of the
recyclability of the complex used. Due to the high solubility of the iron complexes, Fe4–5 in water,
separation and recycling should be possible to perform. Fe5-catalyzed, the reductive alkylation of
N-methylbenzylamine with citronellal, was chosen as a model reaction for this study. At the end of the
first run, ethyl acetate was added under an argon atmosphere to extract the organic compounds, and
the aqueous phase was re-engaged directly in another run after the addition of ammonium formate,
amine, and aldehyde (Table 5). As showed in Table 5, catalytic activity was maintained after five runs
without any decrease in the conversion.
Table 5. Recycling of the pre-catalyst Fe5 a,b
.
Fe5 (2 mol%),
Me3NO (2.5 mol %)
HCO2NH4 (6.5 equiv.)
N
Ph
N
Ph
O
N
Ph
+
+
H
H2O, 90 °C, 24 h
5a
5a'
Entry
Run
Conv. (%) c
Selectivity (5a)/(5a’) c
1
2
3
4
5
1
2
3
4
5
96
95
95
96
98
91/9
96/4
96/4
97/3
96/4
a General conditions for the initial run: citronellal (1 mmol), N-methylbenzylamine (2 equiv.), HCO2NH4 (6.5 equiv.),
b
pre-catalyst Fe5 (2 mol %), Me3NO (2.5 mol %), water (2 mL), 90 ◦C for 24 h. General conditions for run 2–5:
citronellal (1 mmol), N-methylbenzylamine (2 equiv.), HCO2NH4 (6.5 equiv.) were added to the former solution, and
the mixture was heated to 90 ◦C. c Conversion and selectivity were determined by 1H-NMR spectroscopy analysis.
3. Materials and Methods
All air- and moisture-sensitive manipulations were carried out using standard vacuum line
Schlenk tubes techniques. All solvent and substrates were degassed prior to use by bubbling argon
gas directly in the reaction medium. Other solvents and chemicals were purchased from different

Molecules 2020, 25, 421
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suppliers and used as received. Deuterated solvents for NMR spectroscopy were purchased from
Sigma Aldrich (Saint-Quentin Fallavier, France) and used as received. NMR spectra were recorded
on a 500 MHz Bruker spectrometer. Proton (1H) NMR information is given in the following format:
multiplicity (s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet), coupling constant(s) (J) in Hertz
(Hz), number of protons, type. The prefix app is occasionally applied when the true signal multiplicity
was unresolved, and br indicates the signal in question broadened. Carbon (13C) NMR spectra are
reported in ppm (δ) relative to CDCl3 unless noted otherwise. Infrared spectra were recorded over a
PerkinElmer Spectrum 100 FT-IR Spectrometer using neat conditions. HRMS analyses were performed
by using the Laboratoire de Chimie Moléculaire et Thioorganique analytical Facilities.
3.1. General Procedure for the Reduction of Aldehydes
In a dried flamed Schlenk tube under argon, the corresponding aldehyde (1 equiv.) and sodium
formate (5 equiv.) were mixed in water (0.5 M solution). The iron complex Fe4 (2 mol %) and Me3NO
(2.5 mol %) were then added. The mixture was stirred and heated at 80 ◦C for 24 h. After cooling
down to room temperature, the resulting solution was quenched with a saturated aqueous solution of
sodium bicarbonate and extracted three times with ethyl acetate. The organic phase was dried over
MgSO4, filtrated, and concentrated under vacuum to afford the crude product. Purification by flash
chromatography on silica gel furnished the alcohol.
3.2. General Procedure for the Reductive Amination of Aldehydes
In a dried flamed Schlenk tube under argon, the aldehyde (1 equiv.), the amine (2 equiv.) and
ammonium formate (6.5 equiv.) were mixed in water (0.5 M solution). The iron complex Fe5 (2 mol %)
and Me3NO (2.5 mol %) were then added. The mixture was stirred and heated at 90 ◦C for 24–48 h.
After cooling down to room temperature, the resulting solution was quenched with a saturated aqueous
solution of sodium bicarbonate and extracted three times with ethyl acetate. The organic phase was
dried over MgSO4, filtrated, and concentrated under vacuum to afford the crude product. Purification
by flash chromatography on silica gel furnished the amine.
4. Conclusions
In conclusion, we have described the application of water-soluble cyclopentadienone iron
tricarbonyl complexes in the reduction of aldehydes and in reductive amination under hydride transfer
conditions in pure water. Recyclability of iron complex Fe5 was also demonstrated in a model reductive
amination. This system tolerated a variety of functional groups such as halides, ethers, heteroaromatic
derivatives without impeding the chemical yields. These water-soluble iron complexes allow an
efficient, green, and practical procedure for the synthesis of amines and alcohols.
Supplementary Materials: The following are available online. Table S1: Optimization of the reaction conditions
for aldehyde reduction by hydride transfer. Table S2: Optimization of the reaction conditions for reductive
amination by hydride transfer. Figure S1–S64: The 1H, 13C, and 19F-NMR spectra of compounds.
Author Contributions: Conceptualization—J.-L.R. and S.C.; methodology—J.-L.R.; validation—J.-L.R., S.G. and
M.D.M.; formal analysis—S.C. and D.N.; investigation—S.C. and D.N.; resources—J.-L.R.; data curation—S.C.
and D.N.; writing—original draft preparation—J.-L.R.; writing—review and editing—J.-L.R., S.G. and
M.D.M.; visualization—J.-L.R., S.G. and M.D.M.; supervision—J.-L.R.; project administratio—J.-L.R.; funding
acquisition—J.-L.R. and M.D.M. All authors have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Acknowledgments: We gratefully acknowledge financial support from the “Minist
ère de la Recherche et
des Nouvelles Technologies”, Normandie Universit , CNRS, “R gion Normandie”, and the LABEX SynOrg
é
é
(ANR-11-LABX-0029). Ademe Agency is acknowledged for a grant to S. C. and Coopération Française-Sénégal for
a grant to D. N.
Conflicts of Interest: The authors declare no conflict of interest.

Molecules 2020, 25, 421
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Sample Availability: Samples of the compounds are available from the authors.
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