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COMMUNICATION Journal Name
otherwise, the free hemiaminal would be dehydrated and
followed by hydrogenation to tertial amine.
ChemSusChem, 2017, 10, 1969; (f) MD. ORIa: u10s.e1r0,39R/.CE9CckCe0r6t3, 3M9K.
Gerbershagen and M. Niggemann, Angew. Chem. Int. Ed., 2019,
58, 6713.
Our system shows an exceedingly high selectivity towards
the formation of N-substituted lactams, with only a trace
amount of N-substituted pyrrolidine. The unique selectivity of
Ru-L1 catalytic system towards lactam formation probably
benefits from the supporting ligand L1, which brings several
advantages to the system: Firstly, the facial configuration of in-
4
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Crabtree, Organometallics, 2011, 30, 4174; (e) A. Nova, D.
Balcells, N. D. Schley, G. E. Dobereiner, R. H. Carbtree, and O.
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(b) A. J. A. Watson, A. C. Maxwell and J. M. J. Williams, J. Org.
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N. D. Scheley, G. E. Dobereiner and R. H. Crabtree,
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Milstein, J. Am. Chem. Soc., 2018, 140, 11931.
(a) N. A. E.-Jalapa, A. Kumar, G. Leitus, Y. D.-Posner and D.
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Janes, N. A. E.-Jalapa and D. Milstein, J. Am. Chem. Soc., 2018,
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Hong, Angew. Chem. Int. Ed., 2010, 49, 6391.
situ formed Ru-L1 complex provides
a relatively wide
coordination space around Ru,12 thus allowing for
accommodation of the substrates and ligands as geometrically
required. Especially, it may be capable of containing an aminal
alcohol as a ligand around the Ru-bound hemiaminal to
enhance its dehydrogenation to amide. It has been
demonstrated by Crabtree that incorporating a ligand with N-H
protons into the catalyst greatly accelerates amide formation
from the hemiaminal;4d,4e Secondly, the hemilability of the
phosphine moiety could promote both substrate binding, and
more importantly, it would provide the coordination site for cis
β-H elimination; Thirdly, the anchoring effect of the NHC moiety
can stabilize the catalytically active species at high temperature,
which is required for the β-H elimination.4e Furthermore, its
strong σ-donating ability also plays an important role in
facilitating the dehydrogenation of hemiaminal to amide over
the elimination of water,11b and the low product yield with
tripodal triphosphine L3 (entry 6 in Table 1), which has a similar
chelating model with L1 without NHC moiety, further supports
that.
5
6
7
8
9
In conclusion, we have developed the first Ru-catalyzed
synthesis of N-substituted lactams from diols and amines in one
step. The reaction is environmentally benign, with H2 and water
as only byproducts. A careful study on the reaction mechanism
reveals that the acceptorless dehydrogenation of diols might
involve successive N-alkylation and amidation processes to give
the desired products. Further investigations regarding the
reaction mechanism are ongoing.
(a) A. Nandakumar, S. P. Midya, V. G. Landge and E. Balaraman,
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11 (a) J. H. Dam, G. Osztrovszky, L. U. Nordstom, and R. Madsen,
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12 H.-M. Liu, L. Jian, C. Li, C.-C Zhang, H.-Y. Fu, X.-L. Zheng, H.
Chen, and R.-X. Li, J. Org. Chem., 2019, 84, 9151.
We thank the National Natural Science Foundation of China
(21572137 and 21871187) and the Key Program of Sichuan
Science and Technology Project (nos. 2018GZ0312,
2019YFG0146) for financial support. We also acknowledge
Comprehensive Training Platform of Specialized Laboratory,
College of Chemistry, Sichuan University, for HRMS analysis.
13 X.-J. Yu, H.-Y. He, L. Yang, H.-Y. Fu, X.-L. Zheng, H. Chen, R.-X.
Li, Catal. Commun., 2017, 95, 54.
Conflicts of interest
14 (a) M. Varyani, P. K. Khatri, S. L. Jain, Tetrahedron Lett., 2016,
57, 723; (b) J. W. Kim, K. Yamaguchi, and N. Mizuno, Angew.
Chem. Int. Ed., 2008, 47, 9249; (c) R. Ray, S. Chandra, V. Yadav,
P. Mondal, D. Maiti, and G. K. Lahiri, Chem. Commun., 2017,
53, 4006.
15 (a) C. Gunanathan, Y. B.-David and D. Milstein, Science, 2007,
317, 790; (b) M. H. S. A. Hamid, P. A. Slatford and J. M. J.
Williams, Adv. Synth. Catal., 2007, 349, 1555; (c) C.
Gunanathan and D. Milstein, Science, 2013, 341, 1229712.
There are no conflicts to declare.
Notes and references
1
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2
3
D. Astill and V. Boekelheide, J. Am. Chem. Soc., 1955, 77, 4079.
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4 | J. Name., 2012, 00, 1-3 This journal is © The Royal Society of Chemistry 20xx
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