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ChemComm
ESI).
50 This work was supported by the ANR program (ANR-12-BS07-
0011 “IRONHYC”), the CNRS, the UnDivOeIr:s1i0ty.10R39e/nCn4eCsC10,55t1h7eA
Ministère de l’Enseignement Supérieur et de la Recherche and Axa
Scheme 1. Methylation of imine in an one-pot sequence
Research Funds (PhD grant to JZ)
5
Notes and references
55 a UMR 6226 CNRS-Université Rennes 1, Institut des Sciences Chimiques
de Rennes, Team Organometallics: Materials and Catalysis, Centre for
Catalysis and Green Chemistry Campus de Beaulieu, 263 av. du Général
Leclerc, 35042 Rennes Cedex, France Fax: (+) 33 2 23 23 69 39 E-mail:
60
10 Interestingly, this methodology can be applied for the direct one
pot reduction-methylation of imines (Scheme 1): N-
benzylideneaniline can be methylated in the presence of
[CpFe(CO)2(IMes)]I 3 (5 mol%), PhSiH3 (7 equiv.) in 0.5 mL
DMC at 100 C in 48 h under visible light irradiation without
15 isolation of N-benzylaniline intermediate (50% 1H NMR yield with
pyridine as internal standard, 42% isolated yield).
1
(a) M.G. Knize and J. S. Felton, Heterocyclic Amines, in Bioactive
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o
65
70
2
In order to gain insights into the reaction pathway, control
experiments were carried out under neat conditions in the absence
of DMC as C1 source (Scheme 2). The reduction of methyl N-
20 methyl-N-phenylcarbamate led after 24 h to the formation of N,N-
dimethylaniline as the sole product in only 43% conversion
according to crude 1H NMR. Interestingly, the addition of 1 equiv.
of N-methylaniline to the same reaction mixture, and under the
same conditions, led to an increased yield of 72% with a recovery
25 of the secondary amine of 75%. This seems to indicate that the
carbamate is a less reactive intermediate than N,N’-dimethyl-N,N’-
diphenylurea which can be formed in the presence of N-
methylaniline. Indeed, under the standard optimised conditions
without DMC, the reduction of the urea proceeds smoothly with a
30 full conversion: N,N-dimethylaniline can be obtained in 93% yield
and N-methylaniline in 78%. It should be noticed that ureas have
also been considered as intermediates by Beller for the methylation
of amines with CO2 in the presence of hydrosilanes under
ruthenium catalysis.3b,11 It is also noteworthy that, under iron
35 catalysis, organic urea have been reduced to formamidines in the
presence of hydrosilanes which is in contrast with the present
case.12
3
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(a) O. Jacquet, X. Frogneux, C. D. N. Gomes and T. Cantat, Chem.
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Selected reviews: (a) P. Tundo and M. Selva, Acc. Chem. Rev., 2002,
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85
7
8
Selected reviews: (a) B. Schäffner, F. Schäffner, S. P. Verevkin and
A. Börner, Chem. Rev. 2010, 110, 4554; (b) C. Fischmeister and H.
Doucet, Green Chem., 2011, 13, 741.
(a) L. C. Misal Castro, J.-B. Sortais and C. Darcel, Chem. Commun.,
2012, 48, 151; (b) J. Zheng, C. Darcel and J.-B. Sortais,
ChemCatChem, 2013, 5, 2861; (c) B. Li, J.-B. Sortais and C. Darcel,
Chem. Commun., 2013, 49, 3691; (d) H. Jaafar, H. Li, L. C. Misal
Castro, J. Zheng, T. Roisnel, V. Dorcet, J.-B. Sortais and C. Darcel
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90
Scheme 2. Control experimentsa
95
9
(a) F. Jiang, D. Bézier, J.-B. Sortais and C. Darcel, Adv. Synth. Catal.,
2011, 353, 239; (b) D. Bézier, G. T. Venkanna, L. C. Misal Castro, J.
Zheng, J.-B. Sortais and C. Darcel, Adv. Synth. Catal., 2012, 354,
1879; (c) D. Bézier, F. Jiang, T. Roisnel, J.-B. Sortais and C. Darcel,
Eur. J. Inorg. Chem., 2012, 1333; (d) J. Zheng, L. C. Misal Castro, T.
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ChemCatChem, 2011, 3, 1747.
100
105
110
115
40 a Yields were determined by 1H NMR using pyridine as internal standard after workup.
10 (a) H. Li, L. C. Misal Castro, J. Zheng, T. Roisnel, V. Dorcet, J.-B.
Sortais and C. Darcel, Angew. Chem. Int. Ed., 2013, 52, 8045; (b) J.
Zheng, J.-B. Sortais and C. Darcel, ChemCatChem, 2014, 6, 763; (c)
S. Warratz, L. Postigo and B. Royo, Organometallics, 2013, 32, 893.
11 Using the present catalytic system, the methylation of N-methylaniline
with CO2 (3 atm.) at 100 °C with PhSiH3 afforded N,N-dimethylaniline
in 10 % conversion.
In conclusion, an alternative methodology for the methylation of
secondary amines, under hydrosilylation conditions, has been
developed using well-defined iron catalyst and DMC or DEC as
45 the C1 source. This reaction is achieved under milder conditions
than the classical ones involving DMC. It is noteworthy that, in the
present contribution, the C1 building block is the carbonyl moieties
of the carbonate.
12 J. Pouessel, O. Jacquet and T. Cantat, ChemCatChem, 2013, 5, 3552.
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