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COMMUNICATION
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a) R. Grigg, T. R. B. Mitchell, S. Sutthivaiyakit and N. Tongpenyai, J.
observation is consistent with the necessary D–H exchange
and micro reversible nature of the proposed HAT/borrowing
hydrogen mechanism. The intermolecular competitive
reactions between 1a, [D2]-1a and 2a gave kCHH/kCDH =
1.72 on the basis of H NMR analysis. These experimental
findings further confirm that benzylic C−H bond cleavage
Tsuji and Y. Ohsugi, Tetrahedron Lett., 1981, 22, 2667–2670.
DOI: 10.1039/C9CC04120F
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taking part in the rate determining step.
H
D
H
H
Ph
Ph
D
D
+
Ph
[D1]-3a, 8%
Ph
N
Ph
N
Standard Conditions
80% overall yield
+
H
Ph NH2
H
(a)
Ph
OH
[D2]-1a
3a, 0.5%
D
D
2a
3
+
Ph
N
H
[D2]-3a, 91.5%
4
a) H. G. Franck and J. W. Stadelhofer, Industrial Aromatic Chemistry;
Springer-Verlag: Berlin,1988; b) H. Surburg, J. Panten, Common
Fragrance and Flavor Materials, 5th ed., Wiley-VCH: Weinheim, 2006.
M. Christina White, Adv. Synth. Catal., 2016, 358, 2364-2365.
G. A. Filonenko , R. van Putten , E. J. M. Hensena and E. A. Pidko ,
Chem. Soc. Rev., 2018, 47, 1459 - 1483.
H
D
H
H
H
H
Ph
Ph
+
Ph
[D1]-3a, 32%
Ph
N
Ph
OH
Ph
N
H
H
1a
Standard Conditions
78% overall yield
5
6
3a, 55%
(b)
+
Ph NH2
D
D
+
D
D
2a
Ph
N
H
[D2]-3a, 13%
1.00 : 0.58 : 0.24
Ph
OH
KCHH / KCHD = 1.72
7
8
9
For selected reviews, see: a) A. Quintard and J. Rodriguez,
ChemSusChem., 2016, 9, 28−30; b) T. Zell and R. Langer,
ChemCatChem., 2018, 10, 1930−1940; c) F. Kallmeier and R. Kempe,
Angew. Chem. Int. Ed., 2018, 57, 46−60.
[D2]-1a
Scheme 1. Deuterium labelling Studies
For selected Mn-Catalysed processes, see: a) S. Elangovan, J. Neumann,
J.-B. Sortais, K. Junge, C. Darcel and M. Beller, Nat. Commun., 2016, 7,
12641; b) M. Peña-Loṕez, P. Piehl, S. Elangovan, H. Neumann and M.
Beller, Angew. Chem. Int. Ed., 2016, 55, 14967−14971.
For the practical applications of heterogeneous catalysts,
the lifetime of the catalyst and its level of reusability are
key factors. To examine this, the recyclability of nano-Fe2O3
was investigated under the standard reaction conditions
(Table S2, ESI). The cycle was repeated five times and the
isolated yields of the amine products were determined by
column chromatography. Even after five cycles, the
recovered catalyst maintained its catalytic reactivity and the
amine product was obtained above 75% yield (Table S2, entry
5). Thus, the nano-Fe2O3 catalyst could be used at least 5
times without significant changes in its activity. Also, a Hot
filtration test for catalyst leaching was performed for a
standard N-alkylation (Table S3, ESI). The catalyst was
filtered off at 14 h when the product 3a was observed in 43%
yield by gas chromatography. Continuing the reaction in the
absence of the catalyst for the full optimized reaction time,
24 h yielded no significant increase in the yield of the
product (44%). This confirms the true heterogeneous nature
of this catalyst and rules out any catalyst leaching.
Furthermore, we found that this methodology is scalable as
demonstrated by the gram scale synthesis of 3a, 5a and 8a
with 67%, 91% and 92% yields respectively (Table S4, ESI).
In conclusion, by using a commercially available nano-Fe2O3,
we have developed efficient heterogeneous iron catalysed
direct N- and C-alkylation reactions with alcohols via
hydrogen autotransfer for the synthesis of aniline and ketone
derivatives. We have also demonstrated the utility of this
transformation in the synthesis of highly valuable quinoline
systems. Deuterium labeling studies have confirmed that the
present reaction proceeds through hydrogen autotransfer
pathway. Further studies for extending the use of this nano-
Fe2O3 catalyst to other HAT methodologies is currently
underway.
For selected Fe-Catalysed processes, see: a) T. Yan, B. L. Feringa and K.
Barta, Nat. Commun., 2014, 5, 5602; b) A. J. Rawlings, L. J. Diorazio
and M. Wills, Org. Lett., 2015, 17, 1086−1089; c) H. J. Pan, T. W. Ng
and Y. Zhao, Chem. Commun., 2015, 51, 11907−11910; d) S. Elangovan,
J. B. Sortais, M. Beller and C. Darcel, Angew. Chem. Int. Ed., 2015, 54,
14483−14486; e) T. Yan, B. L. Feringa, and K. Barta, ACS Catal., 2016,
6, 381−388; f) 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; g) B. Emayavaramban, M. Sen and B. Sundararaju, Org. Lett.,
2017, 19, 6–9; h) T. Yan, B. L. Feringa and K. Barta, Sci. Adv., 2017, 3,
eaao6494.
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For selected Co-Catalysed processes, see: a) S. Rösler, M. Ertl, T.
Irrgang and R. Kempe, Angew. Chem, Int. Ed., 2015, 54, 15046−15050;
b) N. Deibl and R. Kempe, J. Am. Chem. Soc., 2016, 138, 10786−10789;
c) Z. Yin, H. Zeng, J. Wu, S. Zheng, and G. Zhang, ACS Catal., 2016, 6,
6546−6550.
For selected Ni-Catalysed processes, see: a) F. lonso, , P. Riente and M.
Yus, Synlett., 2007, 12, 1877–1880; b) M. Vellakkaran, K. Singh and D.
Banerjee, ACS Catal., 2017, 7, 8152−8158; c) J. Das, K. Singh, M.
Vellakkaran and D. Banerjee, Org. Lett., 2018, 20, 5587−5591.
D. J. Cole-Hamilton and R. P. Tooze, Catalyst Separation, Recovery and
Recycling, Springer, Dordrecht., 2006.
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a) C. M. Friend and B. Xu, Acc. Chem. Res., 2017, 50 (3), 517–521; b) L.
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Chem., Vol. 50, Springer, 2015; d) R. Shang, L. Illies and E. Nakamura,
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A. Piontek, E. Bisz and M. Szostak,Angew. Chem. Int. Ed., 2018, 57,
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J.J. Sattler, J. Ruiz-Martinez, E. Santillan-Jimenez and B.M.
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Conflicts of interest
There are no conflicts to declare.
Notes and references
4 | J. Name., 2012, 00, 1-3
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