Manganese catalyzed reductive amination of aldehydes using hydrogen as a reductant

Article abstract of DOI:10.1039/c8cc01787e

A one-pot two-step procedure was developed for the alkylation of amines via reductive amination of aldehydes using molecular dihydrogen as a reductant in the presence of a manganese pyridinyl-phosphine complex as a pre-catalyst. After the initial condensation step, the reduction of imines formed in situ is performed under mild conditions (50-100 °C) with 2 mol% of catalyst and 5 mol% of tBuOK under 50 bar of hydrogen. Excellent yields (>90%) were obtained for a large combination of aldehydes and amines (40 examples), including aliphatic aldehydes and amino-alcohols.

Full text of DOI:10.1039/c8cc01787e

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Bruneau-Voisine, D. A. Valyaev, N. Lugan and J. Sortais, Chem. Commun., 2018, DOI:
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Manganese Catalyzed Reductive Amination of Aldehydes using
Hydrogen as Reductant
Duo Wei,a Antoine Bruneau-Voisine,a,b Dmitry A. Valyaev,b Noël Luganb and Jean-Baptiste
Sortais*b,c
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
A one-pot two-steps procedure was developed for the alkylation methanol/amines,18 and multi-component synthesis of
of amines via reductive amination of aldehydes using molecular quinolines,19 pyrroles20 and pyrimidines.21
dihydrogen as reductant in the presence of manganese pyridinyl- Reductive amination22 is one of the chemical reaction in the
phosphine complex as pre-catalyst. After the initial condensation chemist tool-box for the preparation of amines.23 It relies on
step, the reduction of the imines formed in situ is applied under the in situ condensation of a ketone or aldehyde with an amine
mild conditions (50-100 °C) with 2 mol% of catalyst and 5 mol% of to form the corresponding imine, which is subsequently
tBuOK under 50 bar of hydrogen. Excellent yields (> 90%) were reduced to the desired amine. When using molecular
obtained for a large combination of aldehydes and amines (38 hydrogen as reductant, it appears that the key step in the
examples), including aliphatic aldehydes and amino-alcohols.
reaction sequence is the hydrogenation of the intermediate
imine.
In the last two years, the use of manganese as a sustainable
alternative to precious transition metals in hydrogenation and
hydrogen borrowing reactions has achieved an impressive
explosion.1 Starting from the hydrogenation of aldehydes,
ketones and nitriles,2 the scope of reducible functional group
was rapidly enlarged to esters,2d, 3 amides,3c, 4 and CO2.5 Soon
after, hydrogen transfer reactions using isopropanol as
reductant 6 and asymmetric reduction2d, 7 have been disclosed.
In the field of hydrogen borrowing reactions, the first
manganese-catalyzed dehydrogenative coupling of alcohols
and amines to form imines8 was rapidly complemented by the
synthesis of esters9 from alcohols, and amides10 from alcohols
In line with our previous work on manganese catalyzed
reactions24 and catalytic amines synthesis using first-row
transition metals complexes,25 we report thereafter the first
alkylation of amines via reductive amination of aldehydes
using molecular hydrogen as reductant and well-defined
manganese complexes as pre-catalysts.
We have selected complexes 1-4 as candidates for this study
(Scheme 1) as we recently demonstrated that manganese (I)
bromo-tricarbonyl complexes bearing bidendate pyridinyl-
phosphine ligands were good catalysts for the hydrogenation
of carbonyl derivatives, and especially complex
diphenyl-(2-aminopyridinyl)-phosphine ligand.26
2 featuring
and amines. In the field of C-C bond formation reactions,
α-
alkylation of ketones with alcohols,11 and olefination of
nitriles12 were also achieved. Interestingly, the upgrading of
ethanol in butanol,13 the dehydrogenation of methanol14 to H2
and CO2, or the deoxygenation of alcohols15 were also found to
be catalyzed by manganese complexes. Finally, the access to
various higher amine derivatives using alcohols as alkylating
reagents was developed,16 including the N-monomethylation
of amines,16-17 aminomethylation of [hetero]arenes with
Br
Br
Br
Br
N
N
N
N
CO
CO
CO
CO
CO
CO
CO
CO
Mn
Mn
Mn
Mn
HN
HN
P
P
Ph2
P
Ph2
P
Ph2
iPr2
CO
CO
CO
CO
1
2
3
4
Scheme 1. Manganese complexes used in this study.
We initially focused on the direct hydrogenation of N-
benzylideneaniline c1 as model substrate, using catalyst and
2
a base, under 50 bar of H2, based on previously optimized
conditions for the hydrogenation of ketones. First, we found
that alcohols, and notably ethanol, were suitable solvents for
the hydrogenation step (See Table S1 in S.I.) as a green solvent
alternative to toluene. It then appeared that the nature of the
base had little influence on the reaction, NaOtBu, KOtBu,
KHMDS, or Cs2CO3 leading to satisfactory conversions (2 (1
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mol%), base (2 mol%), 100 °C, EtOH, 22h, 41% to 64% yield, used to ensure the full conversion of the aldehyde
see Table S2 in S.I.). The activity of complexes was imines before the hydrogenation step (Table 2). We next
compared at 80 °C with 1 mol% catalyst and 2 mol% of tBuOK probe the scope of this first manganese catalyzed reductive
(Table 1, entries 1-4) and complex appeared to be the most amination system thus defined.
a into the
1-4
c
2
active one. Increasing the catalyst loading to 2 mol% led to a
full conversion (entry 5). Interestingly, the temperature could
be decreased to 50 °C without any detrimental effect on
activity (entry 6), and even to 30 °C where a decent conversion
still occurred (76%, entry 7).
2
(2 mol%),
OH
O
tBuOK (5 mol%)
NH2
H
N
N
+
+
+
H2 (50 bar)
EtOH
a1
b1
c1
d1
e1
Conditions A:
38
29
18
44
Conditions B:
Conditions C:
7
61
11
Table 1. Optimization of the reactions conditions of the hydrogenation of
2
87
benzylideneaniline c1 with manganese catalysts 1-4.
Scheme 2. Optimization of the procedure for reductive amination of
benzaldehyde with aniline under the catalysis of manganese complex . See
main text for conditions definition and SI Table S4 for experimental details.
2
In general, as far as the formation of the imines is not a
limiting step,27 the subsequent hydrogenation proceeds well
for a wide variety of aldehydes and amines (Table 2). First,
benzaldehydes derivatives bearing either electron donating or
electron withdrawing groups both react with anilines to afford
in fine the corresponding amines in good yield (entries 1-16).
Entry[a]
Catalyst
(mol%)
Temperature
(°C)
Time (h)
Yield (%)[c]
1[a]
2[a]
3[a]
4[a]
5[b]
6[b]
7[b]
1
2
3
4
2
2
2
(1)
(1)
(1)
(1)
(2)
(2)
(2)
80
80
80
80
80
50
30
19
24
19
19
17
17
24
40
74
17
Noticeably, halogen substituents (d6-d10), including iodo
substituent, were well tolerated with less than 10%
1
deiodination in the cases of d9 and d10. Esters and amides
> 98
> 98
76
moieties were not reduced under these conditions (d12-d13).
Interestingly, starting from 4-formylacetophenone a14 in the
presence of 2 equivalent of aniline b1, only the aldimine
moieties was reduced in the transient di-imine intermediate
c14 affording the corresponding amino-ketimine d14,28 while
in the presence of 1 equivalent of b1, amino-ketone d15 was
[a] Conditions: an autoclave was charged in a glovebox with, in this order,
c1 (181 mg, 1.0 mmol), EtOH (4.0 mL), Mn-complex (1 mol%), tBuOK (2.2
mg, 2 mol%), and then pressurized with H2 (50 bar) and heated. [b] c1 (91
obtained in good yield.
In the same vein, the reductive
mg, 0.5 mmol), EtOH (2.0 mL),
mol%). [c] Yield was determined by H NMR spectroscopy and GC on the
crude mixture.
2 (5.0 mg, 2 mol%), tBuOK (2.8 mg, 5
1
amination of benzaldehyde a1 with 4-acetyl-aniline b16 led
selectively to the corresponding 4-acetylamine d16 leaving the
ketone
functionality
untouched.
Organometalllic
ferrocenylaldehyde a17 was also suitable for this protocol.
Several heterocycles, including pyrrole, furane, pyridine,
thiophene, and thiazole were well tolerated by the catalytic
system (entries 18-23). It is noteworthy that this reductive
amination protocol is not limited to aniline derivatives, as
sulfonylamide b24 as well as aliphatic primary b25-b27 and
secondary amines b28-b30 were also successfully coupled.
In terms of practical and economical synthesis, direct reductive
amination of aldehydes is more desirable than hydrogenation
of corresponding isolated imines. Hence, we turned our
attention towards the direct synthesis of benzylaniline d1 from
benzaldehyde a1 and aniline b1. In a first attempt, all the
components, i.e. 2, a1, b1, tBuOK, and H2, were introduced in
an autoclave being heated at 80 °C overnight (Scheme 2,
conditions A). Disappointingly, a mixture of benzylalcohol e1
(44%), imine c1 (38%), and the desired amine d1 (18%) was
obtained, showing that the hydrogenation of benzaldehyde
occurred faster than the condensation with aniline. In a second
strategy, the condensation step was carried out in the
presence of the catalyst and the base at 80 °C for 5 h, then the
reaction mixture was pressurized under H2 and stirred at 80 °C
overnight (conditions B). Unfortunately, the main products
were again alcohol e1 (61%) and imine c1 (29%). Finally, we
decided to perform first the condensation of the aldehyde
with the amine in EtOH, imine c1 being formed in 90% yield
after 24 h at 100 °C, and then to add the precatalyst, the base,
and H2 to the crude imine before heating under stirring at 80
°C overnight (Conditions C). To our delight, under these
conditions, the desired N-benzylaniline d1 was obtained in
Ethylenediamine
dibenzylethylenediamine d31, without formation of
imidazolines.29 Remarkably, the amino-alcohols b32
b34 were
b31
afforded
the
N,N’-
-
alkylated to afford selectively the corresponding
hydroxyamines, the pending hydroxy group not entering into a
potentially competitive N-alkylation process.16 To complete
the series of amines amenable for this transformation,
amino-esters b35 b36 were alkylated with success. A series of
aliphalic aldehydes (a37 a40), including butanal (a37), readily
α-
-
-
available by hydroformylation or bio-sourced aldehydes such
cinnamaldehyde (a40), were also successfully engaged in the
present reductive amination protocol. Non-conjugated C=C
were typically not reduced in the course of the reaction, while
conjugated C=C bonds were reduced under harsher
conditions,30 which is in line with the selectivity observed for
the reduction of α,β
-unsatured ketones.26
high yield (87%). Here after, 1.2 equivalent of amines
b were
2 | J. Name., 2012, 00, 1-3
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Table 2. Scope of the reductive amination of aldehydes with amines in presence
of
as precatalyst.[a] ([a] Typical reaction conditions: a solution of aldehyde
(0.5 mmol), amine (0.6 mmol) and anhydrous EtOH (2.0 mL) was stirred at
100 °C for 24h, then transferred to a 20 mL autoclave followed by (5.0 mg, 2
2
a
b
2
mol%) and tBuOK (2.8 mg, 5 mol%). The autoclave was subsequently charged
with H2 (50 bar) and heated. [b] Isolated yield after purification. [c] a1 (4.3
mmol), condensation: 2 h, r.t. [d] c.a. 10% of deiodination product. [e] b1 (100
ꢀ
L, 1.1 mmol). [f] a1 (122 ꢀL, 1.2 mmol). [g] 2 (5 %mol), tBuOK (10 mol%).
Finally, it has to be noted that a few functional groups such as
terminal alkyne, nitro group, or unprotected pyrrole were not
tolerated.
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9. D. H. Nguyen, X. Trivelli, F. Capet, J.-F. Paul, F. Dumeignil and
R. M. Gauvin, ACS Catal., 2017, , 2022-2032.
In conclusion, we have shown that a well-defined manganese
pre-catalyst featuring a readily available bidendate diphenyl-
(2-aminopyridinyl)-phosphine ligand catalyzes efficiently the
reductive amination of aldehydes using H2 as reductant with a
wide functional group tolerance. This higher amines synthesis
protocol significantly enlarges the scope of reactions catalyzed
by manganese complexes and nicely complements a previous
approach based on alkylation of amines with alcohols.
7
10. (a) S. Chakraborty, U. Gellrich, Y. Diskin-Posner, G. Leitus, L.
Avram and D. Milstein, Angew. Chem. Int. Ed., 2017, 56, 4229-
4233; (b) N. A. Espinosa-Jalapa, A. Kumar, G. Leitus, Y. Diskin-
Posner and D. Milstein, J. Am. Chem. Soc., 2017, 139, 11722-
11725; (c) A. Kumar, N. A. Espinosa-Jalapa, G. Leitus, Y. Diskin-
Posner, L. Avram and D. Milstein, Angew. Chem. Int. Ed., 2017,
56, 14992-14996.
11. M. Peña-López, P. Piehl, S. Elangovan, H. Neumann and M.
Beller, Angew. Chem. Int. Ed., 2016, 55, 14967-14971.
12. S. Chakraborty, U. K. Das, Y. Ben-David and D. Milstein, J.
Am. Chem. Soc., 2017, 139, 11710-11713.
Conflicts of interest
13. S. Fu, Z. Shao, Y. Wang and Q. Liu, J. Am. Chem. Soc., 2017,
139, 11941-11948.
There are no conflicts to declare.
14. M. Andérez-Fernández, L. K. Vogt, S. Fischer, W. Zhou, H.
Jiao, M. Garbe, S. Elangovan, K. Junge, H. Junge, R. Ludwig and
M. Beller, Angew. Chem. Int. Ed., 2017, 56, 559-562.
15. J. O. Bauer, S. Chakraborty and D. Milstein, ACS Catal., 2017,
Notes and references
1. (a) D. A. Valyaev, G. Lavigne and N. Lugan, Coord. Chem. Rev.,
2016, 308, 191-235; (b) F. Kallmeier and R. Kempe, Angew.
Chem. Int. Ed., 2018, 57, 46-60; (c) G. A. Filonenko, R. van
Putten, E. J. M. Hensen and E. A. Pidko, Chem. Soc. Rev., 2018,
47, 1459-1483; (d) Y. Li, Y. Hu and X.-F. Wu, Chem. Soc. Rev.,
2018, 47, 172-194.
2. (a) S. Elangovan, C. Topf, S. Fischer, H. Jiao, A. Spannenberg,
W. Baumann, R. Ludwig, K. Junge and M. Beller, J. Am. Chem.
Soc., 2016, 138, 8809-8814; (b) F. Kallmeier, T. Irrgang, T. Dietel
and R. Kempe, Angew. Chem. Int. Ed., 2016, 55, 11806-11809; (c)
A. Bruneau-Voisine, D. Wang, T. Roisnel, C. Darcel and J.-B.
Sortais, Catal. Commun., 2017, 92, 1-4; (d) M. B. Widegren, G. J.
Harkness, A. M. Z. Slawin, D. B. Cordes and M. L. Clarke, Angew.
Chem. Int. Ed., 2017, 56, 5825-5828.
3. (a) S. Elangovan, M. Garbe, H. Jiao, A. Spannenberg, K. Junge
and M. Beller, Angew. Chem. Int. Ed., 2016, 55, 15364-15368; (b)
N. A. Espinosa-Jalapa, A. Nerush, L. J. W. Shimon, G. Leitus, L.
Avram, Y. Ben-David and D. Milstein, Chem. Eur. J., 2017, 23
5934-5938; (c) C. M. Kelly, R. McDonald, O. L. Sydora, M.
Stradiotto and L. Turculet, Angew. Chem. Int. Ed., 2017, 56
7
, 4462-4466.
16. S. Elangovan, J. Neumann, J.-B. Sortais, K. Junge, C. Darcel
and M. Beller, Nat. Commun., 2016, , 12641.
7
17. (a) A. Bruneau-Voisine, D. Wang, V. Dorcet, T. Roisnel, C.
Darcel and J.-B. Sortais, J. Catal., 2017, 347, 57-62; (b) J.
Neumann, S. Elangovan, A. Spannenberg, K. Junge and M. Beller,
Chem. Eur. J., 2017, 23, 5410-5413.
18. M. Mastalir, E. Pittenauer, G. Allmaier and K. Kirchner, J. Am.
Chem. Soc., 2017, 139, 8812-8815.
19. M. Mastalir, M. Glatz, E. Pittenauer, G. Allmaier and K.
Kirchner, J. Am. Chem. Soc., 2016, 138, 15543-15546.
20. F. Kallmeier, B. Dudziec, T. Irrgang and R. Kempe, Angew.
Chem. Int. Ed., 2017, 56, 7261-7265.
21. N. Deibl and R. Kempe, Angew. Chem. Int. Ed., 2017, 56
1663-1666.
,
22. S. Gomez, J. A. Peters and T. Maschmeyer, Adv. Synth.
Catal., 2002, 344, 1037-1057.
23. (a) B. Li, J.-B. Sortais and C. Darcel, RSC Adv., 2016, 6, 57603-
,
57625; (b) S. A. Lawrence, Amines: synthesis, properties and
applications, Cambridge University Press, Cambridge, 2004.
24. (a) J. Zheng, S. Chevance, C. Darcel and J.-B. Sortais, Chem.
Commun., 2013, 49, 10010-10012; (b) J. Zheng, S. Elangovan, D.
A. Valyaev, R. Brousses, V. César, J.-B. Sortais, C. Darcel, N. Lugan
and G. Lavigne, Adv. Synth. Catal., 2014, 356, 1093-1097; (c) D.
A. Valyaev, D. Wei, S. Elangovan, M. Cavailles, V. Dorcet, J.-B.
Sortais, C. Darcel and N. Lugan, Organometallics, 2016, 35, 4090-
4098.
25. (a) H. Jaafar, H. Li, L. C. Misal Castro, J. Zheng, T. Roisnel, V.
Dorcet, J.-B. Sortais and C. Darcel, Eur. J. Inorg. Chem., 2012,
3546-3550; (b) B. Li, J.-B. Sortais, C. Darcel and P. H. Dixneuf,
ChemSusChem, 2012, 5, 396-399; (c) L. C. Misal Castro, J.-B.
Sortais and C. Darcel, Chem. Commun., 2012, 48, 151-153; (d) L.
,
15901-15904; (d) R. van Putten, E. A. Uslamin, M. Garbe, C. Liu,
A. Gonzalez-de-Castro, M. Lutz, K. Junge, E. J. M. Hensen, M.
Beller, L. Lefort and E. A. Pidko, Angew. Chem. Int. Ed., 2017, 56
7531-7534.
,
4. V. Papa, J. R. Cabrero-Antonino, E. Alberico, A. Spanneberg, K.
Junge, H. Junge and M. Beller, Chem. Sci., 2017, , 3576-3585.
5. (a) S. Kar, A. Goeppert, J. Kothandaraman and G. K. S. Prakash,
ACS Catal., 2017, , 6347-6351; (b) A. Dubey, L. Nencini, R. R.
Fayzullin, C. Nervi and J. R. Khusnutdinova, ACS Catal., 2017,
8
7
7,
3864-3868; (c) F. Bertini, M. Glatz, N. Gorgas, B. Stoger, M.
Peruzzini, L. F. Veiros, K. Kirchner and L. Gonsalvi, Chem. Sci.,
2017, 8, 5024-5029.
6. (a) M. Perez, S. Elangovan, A. Spannenberg, K. Junge and M.
Beller, ChemSusChem, 2017, 10, 83-86; (b) A. Bruneau-Voisine,
D. Wang, V. Dorcet, T. Roisnel, C. Darcel and J.-B. Sortais, Org.
Lett., 2017, 19, 3656-3659.
7. (a) A. Zirakzadeh, S. R. M. M. de Aguiar, B. Stöger, M. Widhalm
and K. Kirchner, ChemCatChem, 2017, 9, 1744-1748; (b) D.
Wang, A. Bruneau-Voisine and J.-B. Sortais, Catal. Commun.,
2018, 105, 31-36; (c) M. Garbe, K. Junge, S. Walker, Z. Wei, H.
Jiao, A. Spannenberg, S. Bachmann, M. Scalone and M. Beller,
Angew. Chem. Int. Ed., 2017, 56, 11237-11241.
8. (a) A. Mukherjee, A. Nerush, G. Leitus, L. J. W. Shimon, Y. Ben
David, N. A. Espinosa Jalapa and D. Milstein, J. Am. Chem. Soc.,
2016, 138, 4298-4301; (b) M. Mastalir, M. Glatz, N. Gorgas, B.
Stöger, E. Pittenauer, G. Allmaier, L. F. Veiros and K. Kirchner,
Chem. Eur. J., 2016, 22, 12316-12320; (c) U. K. Das, Y. Ben-David,
Y. Diskin-Posner and D. Milstein, Angew. Chem. Int. Ed., 2018,
DOI: 10.1002/anie.201712593.
P. Bheeter, M. Henrion, M. J. Chetcuti, C. Darcel, V. Ritleng and
J.-B. Sortais, Catal. Sci. Technol., 2013, 3, 3111-3116; (e) J. Zheng,
T. Roisnel, C. Darcel and J. B. Sortais, ChemCatChem, 2013,
5
,
2861-2864; (f) J. Zheng, C. Darcel and J.-B. Sortais, Chem.
Commun., 2014, 50, 14229-14232.
26. D. Wei, A. Bruneau-Voisine, T. Chauvin, V. Dorcet, T. Roisnel,
D. Valyaev, N. Lugan and J.-B. Sortais, Adv. Synth. Catal., 2018,
360, 676-681.
27.
For benzaldehydes derivatives with anilines, the
condensation may be carried out at r.t. in 1 h, see table 2, entry
4.
28. Ketimines are not reduced under these conditions, see Table
S5 in SI.
29. M. Ishihara and H. Togo, Tetrahedron, 2007, 63, 1474-1480.
30. Under standard conditions, c.a. 10% of unsatured amine
d40' was identified in the crude mixture.
4 | J. Name., 2012, 00, 1-3
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• A table of contents entry: graphic maximum size 8 cm x 4 cm and one
sentence of text, maximum 20 words, highlighting the novelty of the work
First alkylation of amines via reductive amination of aldehydes catalysed by manganese
bidendate pyridinyl-phosphine complex