10.1002/cctc.201700545
ChemCatChem
COMMUNICATION
In the plot of conversion vs. time shown in Figure 2 (trace ) it
can be noted that the reaction has a long induction time (about 3
h). Notably, this induction period remained the same
independent of the complexation time of (S,S)-L with
RuCl3(H2O)x under Ar atmosphere preceding the introduction of
H2 in the reaction vessel. However, the induction time
disappeared when RuCl3(H2O)x was pre-treated with refluxing
[1]
[2]
Asymmetric Catalysis on Industrial Scale, 2nd ed. (“Challenges,
approaches, Solutions”) (Eds.: H.-U. Blaser, H.-J. Federsel), Wiley-
VCH, Weinheim, 2010.
For
a comprehensive review of the topic, see: a) Handbook of
Homogeneous Hydrogenation (Eds.: J. G. de Vries, C. J. Elsevier),
Wiley-VCH, Weinheim, 2007. b) D. J. Ager, A. H. M. de Vries J. G. de
Vries, Chem. Soc. Rev., 2012, 41, 3340–3380.
iPrOH (i.e.,
a reducing agent), before carrying out the
[3]
For contributions from our research groups, see: a) P. Gajewski, M.
Renom-Carrasco, S. Vailati Facchini, L. Pignataro, L. Lefort, J. G. de
Vries, R. Ferraccioli, U. Piarulli, C. Gennari, Eur. J. Org. Chem. 2015,
5526-5536; b) P. Gajewski, M. Renom-Carrasco, S. Vailati Facchini, L.
Pignataro, L. Lefort, J. G. de Vries, R. Ferraccioli, A. Forni, U. Piarulli,
C. Gennari, Eur. J. Org. Chem. 2015, 1887-1893; c) P. Gajewski, A.
Gonzalez-de-Castro, M. Renom-Carrasco, U. Piarulli, C. Gennari, J. G.
de Vries, L. Lefort, L. Pignataro, ChemCatChem 2016, 8, 3431-3435.
For selected examples from the literature, see: a) R. H. Morris, Acc.
Chem. Res. 2015, 48, 1494-1502, and references therein; b) T. Zell, D.
Milstein, Acc. Chem. Res. 2015, 48, 1979-1994, and references
therein; c) Y.-Y. Li, S.-L. Yu, W.-Y. Shen, J.-X. Gao, Acc. Chem. Res.
2015, 48, 2587-2598, and references therein; d) R. Hodgkinson, A. Del
Grosso, G. Clarkson, M. Wills, Dalton Trans. 2016, 45, 3992-4005 and
references therein; e) J. P. Hopewell, J. E. D. Martins, T. C. Johnson, J.
Godfrey, M. Wills, Org. Biomol. Chem. 2012, 10, 134-145; f) A.
Berkessel, S. Reichau, A. von der Hꢀh, N. Leconte, J.-M. Neudꢀrfl,
Organometallics 2011, 30, 3880-3887; g) M. Shevlin, M. R. Friedfeld,
H. Sheng, N. A. Pierson, J. M. Hoyt, L.-C. Campeau, P. J. Chirik, J.
Am. Chem. Soc. 2016, 138, 3562-3569; h) J. M. Hoyt, M. Shevlin, G.
W. Margulieux, S. W. Krska, M. T. Tudge, P. J. Chirik, Organometallics
2014, 33, 5781-5790; i) A. Naik, T. Maji, O. Reiser, Chem. Commun.
2010, 46, 4475-4477.
hydrogenation under the optimized conditions (Figure 2, trace
). This finding suggests that formation of the hydrogenation
catalyst occurs after reduction of RuCl3(H2O)x to a lower-valent
species, probably Ru(II). The conversion plot appears to obey to
a zero-order kinetic law in the 0-75% conversion range.
Unfortunately, our attempts to isolate and/or characterize the
active complex were unsuccessful due to its high sensitivity.
In summary, we have described a new ruthenium-catalyzed
AH of ketones based on the use of the Trost ligand (S,S)-L,
which had so far never found application in metal-catalyzed
reductions. The new RuCl3(H2O)x/(S,S)-L catalytic system can
be readily prepared in situ and provides access to a range of
chiral alcohols with good conversions and high enantioselectivity
(up to 96% ee). Kinetic studies demonstrate that formation of the
catalytically active species takes place slowly in the presence of
H2. Compared to numerous other known methodologies for
ketone AH,[10] the one described in this paper has the advantage
of employing a commercially available chiral ligand (L) and a Ru
source [RuCl3(H2O)x] which is the cheapest available on the
market. Therefore, our new methodology represents a step
forward to address the catalyst cost issues that often discourage
the industrial use of asymmetric catalysis.
[4]
[5]
[6]
a) J. G. de Vries, A. H. M. de Vries, Eur. J. Org. Chem. 2003, 799-811;
b) H.-U. Blaser, Chem. Commun. 2003, 293-296.
a) B. M. Trost, D. L. Van Vranken, Angew. Chem. Int. Ed. 1992, 31,
228-230; Angew. Chem. 1992, 104, 194-196; c) B. M. Trost, D. L. Van
Vranken, C. Bingel, J. Am. Chem. Soc. 1992, 114, 9327-9343.
For recent reviews on allylic alkylation reactions, see: a) B. M. Trost,
Tetrahedron 2015, 71, 5708-5733; b) J. Tsuji, Tetrahedron 2015, 71,
6330-6348.
Experimental Section
[7]
[8]
General Procedure for Hydrogenation.
For examples of use of the Trost ligand in reactions different from AAA,
see: a) J. M. Longmire, B. Wang, X. Zhang, J. Am. Chem. Soc. 2002,
124, 13400-13401; b) B. H. Lipshutz, K. Noson, W. Chrisman, A. Lower,
J. Am. Chem. Soc. 2003, 125, 8779-8789; c) T. Ireland, F. Fontanet,
G.-G. Tchao, Tetrahedron Lett. 2004, 45, 4383-4387; d) R. T. Stemmler,
C. Bolm, Adv. Synth. Catal. 2007, 349, 1185-1198; e) M. M. P. Grutters,
J. I. van der Vlugt, Y. Pei, A. M. Mills, M. Lutz, A. L. Spek, C. Müller, C.
Moberg, D. Vogt, Adv. Synth. Catal. 2009, 351, 2199-2208; f) A.
Faulkner, J. F. Bower, Angew. Chem. Int. Ed. 2012, 51, 1675-1679;
Angew. Chem. 2012, 124, 1707-1711; g) D. Huang, X. Liu, L. Li, Y. Cai,
W. Liu, Y. Shi, J. Am. Chem. Soc. 2013, 135 , 8101-8104.
For two unsuccessful attempts to use L as ligand for hydrogenation,
see: a) C. de Bellefon, T. Lamouille, N. Pestre, F. Bornette, H.
Pennemann, F. Neumann, V. Hessel, Catal. Today 2005, 110, 179-187;
b) C.-C. Tai, J. Pitts, J. C. Linehan, A. D. Main, P. Munshi, P. G.
Jessop, Inorg. Chem. 2002, 41, 1606-1614.
In a Schlenk vessel under argon atmosphere, a stock solution of
catalyst was prepared dissolving RuCl3(H2O)x (2.7 mg, 0.01
mmol), ligand (S,S)-L (6.9 mg, 0.01 mmol) and Na2CO3 (5.3 mg
0.05 mmol) in 5 mL of dry methanol. The solution was stirred for
45 min at room temperature, and then 0.5 mL-aliquots (each
corresponding to 0.001 mmol / 0.01 equiv of [Ru]) were
dispensed into vials containing the freshly distilled substrate(s)
(0.1 mmol, 1 equiv) placed into an argon-filled vessel. The vials
were transferred into an autoclave, which was purged three
times with H2 and then pressurized to 30 bar and magnetically
stirred at room temperature for 22 h. After venting H2,
hexadecane (0.1 mmol) was added in each vial and GC analysis
was performed. The ee values determined by chiral GC or HPLC
(see the Supporting Information for detail).
[9]
[10] For recent reviews on the asymmetric hydrogenation of ketones, see:
a) R. Noyori, Angew. Chem. Int. Ed. 2013, 52, 79-92; Angew. Chem.
2013, 125, 83-98; b) J.-H. Xie, D.-H. Bao, Q.-L. Zhou, Synthesis 2015,
47, 460-471; c) P.-G. Echeverria, T. Ayad, P. Phansavath, V.
Ratovelomanana-Vidal, Synthesis 2016, 48, 2523-2539; d) Refs. [4a,c].
[11] For recent examples of enantioselective ruthenium-catalyzed ketone
hydrogenations, see: a) R. J. Hamilton, S. H. Bergens, J. Am. Chem.
Soc. 2006, 128, 13700-13701; b) N. Arai, M. Akashi, S. Sugizaki, H.
Ooka, T. Inoue, T. Ohkuma, Org. Lett. 2010, 12, 3380-3383; c) B.
Stegink, L. van Boxtel, L. Lefort, A. J. Minnaard, B. L. Feringa, J. G. de
Vries, Adv. Synth. Catal. 2010, 352, 2621-2628; d) W. Li, G. Hou, C.
Wang, Y. Jiang, X. Zhang, Chem. Commun. 2010, 46, 3979-3981; e) Y.
Li, Y. Zhou, Q. Shi, K. Ding, R. Noyori, C. A. Sandoval, Adv. Synth.
Catal. 2011, 353, 495-500.
Acknowledgements
This project has received funding from the European Union’s
Horizon 2020 research and innovation programme under the
Marie Skłodowska-Curie Grant Agreement No. [ITN-EID
“REDUCTO” PITN-GA-2012-316371] and was also supported by
an Erasmus+ Placement predoctoral fellowship (to M. C.). L. P.
We thank the Dipartimento di Chimica, Università di Milano, for
financial support (Piano di Sviluppo dell’Ateneo 2015/2017-Linea
2/Azione B).
Keywords: ruthenium • hydrogenation • asymmetric catalysis •
[12] Several ruthenium-based catalysts have been reported to promote the
AH of aromatic ketones with >99% ee and low catalyst loadings (S/C
ketones • Trost ligand
This article is protected by copyright. All rights reserved.