Organometallics
Communication
reduce the reaction temperature, preferably to as low as 20−40
Paneque-Sosa, M.; Lopez-Poveda, M. J. Chem. Soc., Dalton Trans.
1
(
2
(
989, 489−495.
3) Zhang, J.; Leitus, G.; Ben-David, Y.; Milstein, D. J. Am. Chem. Soc.
005, 127, 10840−10841.
4) (a) Zhang, J.; Gandelman, M.; Shimon, L. J. W.; Milstein, D.
°C, and (b) reduce the catalyst loading, preferably to less than
0
4
.05 mol %. Guided by these considerations, we tested complex
in the hydrogenation of several benchmark substrates of
Scheme 3, all at 40 °C.
Dalton Trans. 2007, 107−113. (b) Zhang, J.; Balaraman, E.; Leitus, G.;
Milstein, D. Organometallics 2011, 30, 5716−5724. (c) Gunanathan,
C.; Shimon, L. J. W.; Milstein, D. J. Am. Chem. Soc. 2009, 131, 3146−
To our satisfaction, the results of the hydrogenation
experiments of Scheme 3 fully support the expectation behind
this work that an outstanding ethanol dehydrogenation catalyst
might also have superior efficiency in hydrogenation of
substrates with polar CX bonds. Catalyst 4 is particularly
successful for the reduction of alkanoates, giving an
unprecedented 20 000 turnovers in 16 h for ethyl acetate and
3
́
147. (d) del Pozo, C.; Iglesias, M.; Sanchez, F. Organometallics 2011,
30, 2180−2188. (e) Musa, S.; Shaposhnikov, I.; Cohen, S.; Gelman, D.
Angew. Chem., Int. Ed. 2011, 50, 3533−3537. (f) Nielsen, M.; Kammer,
A.; Cozzula, D.; Junge, H.; Gladiali, S.; Beller, M. Angew. Chem., Int.
Ed. 2011, 50, 9593−9597.
(5) (a) Kuriyama, W.; Matsumoto, T.; Ogata, O.; Ino, Y.; Aoki, K.;
1
8 800 turnovers in 18 h for methyl hexanoate, both at 40 °C.
The best TON reported to date for this type of substrate was
100 in 18 h at 100 °C for methyl hexanoate, using a ruthenium
Tanaka, S.; Ishida, K.; Kobayashi, T.; Sayo, N.; Saito, T. Org. Process
Res. Dev. 2012, 16, 166 −171. (b) Spasyuk, D.; Smith, S.; Gusev, D. G.
Angew. Chem., Int. Ed. 2012, 51, 2772−2775. (c) Nielsen, M.; Junge,
H.; Kammer, A.; Beller, M. Angew. Chem., Int. Ed. 2012, 51, 5711−
7
5b
dimer analogous to VI, {RuH(CO)[N(C H PiPr ) ]} . For
2
4
2 2
2
another comparison, the best Firmenich catalyst,
RuCl (H NC H PPh ) , would theoretically need 27 h to
5
713.
2
2
2
4
2 2
(6) (a) Bertoli, M.; Choualeb, A.; Gusev, D. G.; Lough, A. J.; Major,
produce 18 600 turnovers for methyl octanoate at 100 °C, on
Q.; Moore, B. Dalton Trans. 2011, 40, 8941 −8949. (b) Bertoli, M.;
Choualeb, A.; Lough, A. J.; Moore, B.; Spasyuk, D.; Gusev, D. G.
Organometallics 2011, 30, 3479 −3482.
−1
the basis of the reported TOF = 688 h over a 2.5 h reaction
1
2c
time. Complex 4 is also a competent imine hydrogenation
catalyst, giving a particularly high TON = 50 000 for N-
benzylaniline.
(7) Zhang, D. L.; Deng, Y. F.; Li, C. B.; Chen, J. Ind. Eng. Chem. Res.
2
(
008, 47, 1995−2001.
8) An equilibrium between ethanol, acetaldehyde, and 1-
ethoxyethanol is slow on the NMR time scale. We estimated K =
.6 ± 0.05 (ΔG = −0.3 kcal/mol) at room temperature, using a
sample of 63 mg of acetaldehyde in 727 mg of ethanol.
9) (a) Blaquiere, N.; Diallo-Garcia, S.; Gorelsky, S. I.; Black, D. A.;
In conclusion, this paper presents the air-stable catalyst
RuCl (PPh )[PyCH NHC H PPh ] (4), which can be pre-
2
3
2
2
4
2
0
pared on a large scale from inexpensive and readily available
starting materials, following the methods developed in this
work. Complex 4 is an outstanding versatile catalyst for alcohol
dehydrogenation and for reduction of compounds with polar
CX bonds. Catalyst 4 has unprecedented efficiency for
acceptorless dehydrogenative coupling of ethanol under reflux
(
Fagnou, K. J. Am. Chem. Soc. 2008, 130, 14034−14035. (b) Conley, B.
L.; Guess, D.; Williams, T. J. J. Am. Chem. Soc. 2011, 133, 14212−
14215.
(10) Zweifel, T.; Naubron, J.-V.; Bu
H. Angew. Chem., Int. Ed. 2008, 47, 3245−3249.
11) (a) Zhang, J.; Leitus, G.; Ben-David, Y.; Milstein, D. Angew.
̈ ̈
ttner, T.; Ott, T.; Grutzmacher,
(
TON up to 17 000) and for hydrogenation of esters and
(
imines while using as low as 50 ppm [Ru] under mild
conditions.
Chem., Int. Ed. 2006, 45, 1113−1115. (b) Balaraman, E.; Gunanathan,
C.; Zhang, J.; Shimon, L. J. W.; Milstein, D. Nature Chem. 2011, 3, 609
−
614. (c) Fogler, E.; Balaraman, E.; Ben-David, Y.; Leitus, G.; Shimon,
ASSOCIATED CONTENT
Supporting Information
Text, figures, tables, and a CIF file giving experimental and
■
L. J. W.; Milstein, D. Organometallics 2011, 30, 3826−3833.
(d) Gunanathan, C.; Milstein, D. Acc. Chem. Res. 2011, 44, 588−602.
(12) (a) Saudan, L. A.; Saudan, C. M.; Debieux, C.; Wyss, P. Angew.
Chem., Int. Ed. 2007, 46, 7473−7476. (b) Saudan, L.; Dupau, P.;
Riedhauser, J.-J.; Wyss, P. (Firmenich SA) WO 2006106483, 2006.
*
S
(c) Saudan, L.; Dupau, P.; Riedhauser, J.-J.; Wyss, P. (Firmenich SA)
US 2010280273, 2010.
AUTHOR INFORMATION
■
(13) (a) Kuriyama, W.; Ino, Y.; Ogata, O.; Sayo, N.; Saitoa, T. Adv.
Synth. Catal. 2010, 352, 92−96. (b) Ino, Y.; Kuriyama, W.; Ogata, O.;
Matsumoto, T. Top. Catal. 2010, 53, 1019−1024. (c) Kuriyama, W.;
Matsumoto, T.; Ino, Y.; Ogata, O.; Saeki N. (Takasago Int. Co.) WO
*
Author Contributions
2
(
011048727, 2011.
14) (a) Sun, Y.; Koehler, C.; Tan, R.; Annibale, V. T.; Song, D.
The manuscript was written through contributions of both
authors. Both authors have given approval to the final version
of the manuscript.
Chem. Commun. 2011, 47, 8349−8351. (b) Stempfle, F.; Quinzler, D.;
Heckler, I.; Mecking, S. Macromolecules 2011, 44, 4159−4166.
(c) Hanton, M. J.; Tin, S.; Boardman, B. J.; Miller, P. J. Mol. Catal.
A 2011, 346, 70−78. (d) O, W. W. N.; Lough, A. J.; Morris, R. H.
Chem. Commun. 2010, 46, 8240−8242. (e) Touge, T.; Hakamata, T.;
Nara, H.; Kobayashi, T; Sayo, N.; Saito, T.; Kayaki, Y.; Ikariya, T. J.
Am. Chem. Soc. 2011, 133, 14960−14963. (f) Ito, M.; Ootsuka, T.;
Watari, R.; Shiibashi, A.; Himizu, A.; Ikariya, T. J. Am. Chem. Soc. 2011,
133, 4240−4242. (g) Takebayashi, S.; Bergens, S. H. Organometallics
2009, 28, 2349−2351. (h) Teunissen, H.; Elsevier, C. J. Chem.
Commun. 1988, 1367−1368.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We are grateful to the NSERC of Canada, the Ontario
Government, and Wilfrid Laurier University for financial
support.
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dx.doi.org/10.1021/om300670r | Organometallics 2012, 31, 5239−5242