ACS Catalysis
Letter
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(13) The product N-ethylaniline (2a) could not convert to
N-phenylacetamide (1a) with one equivalent H2O under the reaction
conditions in 24 h.
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(15) In the hydrogenation of 4-acetamidobenzoate, the deoxygena-
tive reduction product, methyl 4-(ethylamino)benzoate was obtained
in 15% yield; the main byproduct was the ester reduction product,
N-(4-(hydroxymethyl)phenyl)acetamide (80%).
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(16) B(C6F5)3 is known to be able to abstract hydrides from some
organometallic species; for ref see: Yang, X.; Stern, C. L.; Marks, T. J.
Angew. Chem., Int. Ed. Engl. 1992, 31, 1375−1377 The chloroiridium
hydride complex 6b and its corresponding iridium dihydride
complexes reacted with B(C6F5)3 in toluene-d8 at 120 °C for 4 h,
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1
and no change was observed in both H and 31P NMR spectra..
(17) For the mechanism study of the ruthenium-catalyzed hydro-
(6) For selected examples, see: (a) Ito, M.; Sakaguchi, A.; Kobayashi,
C.; Ikariya, T. J. Am. Chem. Soc. 2007, 129, 290−291. (b) Ito, M.; Koo,
L. W.; Himizu, A.; Kobayashi, C.; Sakaguchi, A.; Ikariya, T. Angew.
Chem., Int. Ed. 2009, 48, 1324−1327. (c) Ito, M.; Kobayashi, C.;
Himizu, A.; Ikariya, T. J. Am. Chem. Soc. 2010, 132, 11414−11415.
(d) Balaraman, E.; Gnanaprakasam, B.; Shimon, L. J. W.; Milstein, D. J.
Am. Chem. Soc. 2010, 132, 16756−16758. (e) John, J. M.; Bergens, S.
H. Angew. Chem., Int. Ed. 2011, 50, 10377−10380. (f) Kita, Y.;
Higuchi, T.; Mashima, K. Chem. Commun. 2014, 50, 11211−11213.
(g) Cabrero-Antonino, J. R.; Alberico, E.; Drexler, H.-J.; Baumann, W.;
Junge, K.; Junge, H.; Beller, M. ACS Catal. 2016, 6, 47−54.
(7) (a) Magro, A. A. N.; Eastham, G. R.; Cole-Hamilton, D. J. Chem.
Commun. 2007, 43, 3154−3156. (b) Coetzee, J.; Dodds, D. L.;
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Junge, K.; Junge, H.; Beller, M. Chem. Sci. 2016, 7, 3432−3442. (e)
Recently, Beller reported a reductive coupling of acids and amines to
produce amines using H2 and the Ru-triphos catalysts. Catalytic
hydrogenation of amide formed in situ is suggested as one of the
pathways for the reaction, see: Sorribes, I.; Cabrero-Antonino, J. R.;
Vicent, C.; Junge, K.; Beller, M. J. Am. Chem. Soc. 2015, 137, 13580−
13587.
genation of amides, see ref 7b.
(18) When heating the mixture of N-phenylacetamide and one
equivalent B(C6F5)3 mixed in toluene-d8 at 120 °C for 10 h, server
rotational isomers of the boron-amide adduct were observed by
carefully checking the NMR spectrum.
(19) For other iridium-catalyzed hydrogenation involving hetero-
cleavage of the coordinated H2, see: (a) Dobereiner, G. E.; Nova, A.;
Schley, N. D.; Hazari, N.; Miller, S. J.; Eisenstein, O.; Crabtree, R. H. J.
Am. Chem. Soc. 2011, 133, 7547−7562. (b) Manas, M. G.; Graeupner,
J.; Allen, L. J.; Dobereiner, G. E.; Rippy, K. C.; Hazari, N.; Crabtree, R.
H. Organometallics 2013, 32, 4501−4506.
(20) Using catalytic amount of B(C6F5)3 was tested. When 10 mol%
B(C6F5)3 and 20 mol% scavengers to remove the formed water was
used in the iridium-catalyzed hydrogenation of N-phenylacetamide
(1a), moderate conversion (31−64%) and selectivity (4:1−30:1) were
achieved. For details, see SI, Table S4.
(8) (a) Liu, C.; Xie, J.-H.; Li, Y.-L.; Chen, J.-Q.; Zhou, Q.-L. Angew.
Chem., Int. Ed. 2013, 52, 593−596. (b) Yang, X.-H.; Xie, J.-H.; Liu,
W.-P.; Zhou, Q.-L. Angew. Chem., Int. Ed. 2013, 52, 7833−7836. (c) Li,
W.; Xie, J.-H.; Yuan, M.-L.; Zhou, Q.-L. Green Chem. 2014, 16, 4081−
4085. (d) Liu, C.; Xie, J.-H.; Tian, G.-L.; Li, W.; Zhou, Q.-L. Chem. Sci.
2015, 6, 2928−2931.
(9) For other applications of the complexes 4−6, see refs 8c, 8d, and:
(a) Gupta, M.; Hagen, C.; Kaska, W. C.; Cramer, R. E.; Jensen, C. M.
J. Am. Chem. Soc. 1997, 119, 840−841. (b) Gottker-Schnetmann, I.;
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White, P.; Brookhart, M. J. Am. Chem. Soc. 2004, 126, 1804−1811.
(c) Gottker-Schnetmann, I.; Brookhart, M. J. Am. Chem. Soc. 2004,
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126, 9330−9338. (d) Morales-Morales, D.; Redon, R. o.; Yung, C.;
Jensen, C. M. Inorg. Chim. Acta 2004, 357, 2953−2956. (e) Tanaka,
R.; Yamashita, M.; Nozaki, K. J. Am. Chem. Soc. 2009, 131, 14168−
14169.
(10) Lewis acids promote nucleophilic additions of amides by
organometallic reagents; for ref see: Pace, V.; Holzer, W.; Olofsson, B.
Adv. Synth. Catal. 2014, 356, 3697−3736. Amide can form a stable
boron-amide adduct with B(C6F5)3; for ref see: Parks, D. J.; Piers, W.
E.; Parvez, M.; Atencio, R.; Zaworotko, M. J. Organometallics 1998, 17,
1369−1377.
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ACS Catal. 2016, 6, 3665−3669