Journal of the American Chemical Society
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As is well known, longer-chain alcohols like 1-hexanol and 1-
1
2
3
4
5
6
7
8
octanol are more similar to gasoline than 1-butanol, and have
higher energy densities (see SI). To obtain higher conversion
to longer-chain alcohols, more EtONa was used, with results
shown in Table 2. Obviously, more EtONa helps increasing
the conversions of ethanol and the yields of hexanols and
octanols. Thus, using 20 mol% of EtONa, 28.2 % yield of hex-
anol (C6) and 9.4 % yield of octanol (C8) were obtained, to-
gether with 35.8% yield of 1-butanol (Table 2). With these
results, this reaction system can be counted as the most effi-
cient process for making hexanol and octanol directly from
ethanol through a Guerbet-type reaction.
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(5) (a) Weizmann, C. GB 191504845 A, 1919 (b) Jin, C.; Yao, M.; Liu,
H.; Lee, C.-F.; Ji, J. Renewable Sustainable Energy Rev. 2011, 15,
4080−4106.
In conclusion, we have developed a very efficient pincer-
ruthenium catalyzed Guerbet-type process for production of
biofuel from ethanol with the highest TON (18209; 86.1%
selectivity to 1-butanol) of a Guerbet-type reaction. By in-
creasing the amount of catalytic base, the amount of C6 and
C8 alcohols increases substantially, reaching a record total
conversion of 73.4% (37.6% selectivity to C6+C8 alco-
hols) .Our mechanistic studies, including complex isolation
from the catalytic reaction, show that the likely actual cata-
lyst is the dearomatized [Ru]-7, and indicate that the major
deactivation pathway is consumption of the strong base by
catalytic reaction of the formed water with ethanol and
EtONa to form inactive NaOAc.
(6) (a) Guerbet, M. C. R. Acad. Sci. Paris 1899, 128, 1002−1004; (b)
Guerbet, M. M. C. R. Acad. Sci. Paris 1909, 149, 129−132; (c) Veibel, S.;
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D.; Shou, H.; Davis, R. J. ACS Catal. 2015, 5, 1737−1746; (h) Gabriels,
D.; Hernandez, W. Y.; Sels, B.; Van Der Voort, P.; Verberckmoes, A.
Catal. Sci. Technol. 2015, 5, 3876−3902.
(7) For ruthenium catalyzed upgrading of ethanol see: (a) Dowson,
G. R. M.; Haddow, M. F.; Lee, J.; Wingad, R. L.; Wass, D. F. Angew.
Chem., Int. Ed. 2013, 52, 9005−9008; (b) Wingad, R. L.; Gates, P. J.;
Street, S. T. G. Wass, D. F. ACS Catal. 2015, 5, 5822−5826; (c) Tseng,
K. T.; Lin, S.; Kampf, J. W.; Szymczak, N. K. Chem. Commun., 2016,
52, 2901-2904; (d) Wingad, R. L.; Bergstrom, E. J. E.; Everett. M.;
Pellow, K. J.; Wass, D. F. Chem. Commun., 2016, 52. 5202−5204.
(8) For iridium catalyzed upgrading of ethanol see: (a) Koda, K.;
Matsu-ura, T.; Obora, Y.; Ishii, Y. Chem. Lett. 2009, 38, 838-839; (b)
Xu, G.; Lammens, T.; Liu, Q.; Wang, X. Dong, L.; Caiazzo, A.; Ashraf,
N.; Guan, J.; Mu, X. Green Chem., 2014, 16, 3971–3977; (c)
Chakraborty, S.; Piszel, P. E.; Hayes, C. E.; Baker, R. T.; Jones, W. D. J.
Am. Chem. Soc. 2015, 137, 14264−14267.
(9) A review of heterogeneously catalyzed upgrading of ethanol:
Galadima, A.; Muraza, O. Ind. Eng. Chem. Res. 2015, 54, 7181−7194.
(10) (a) Zhang, J; Leitus, G; Ben-David, Y; Milstein, D. J. Am. Chem.
Soc. 2005, 127, 10840-10841; (b) Gunanathan, C; Ben-David, Y; Mil-
stein, D. Science 2007, 317, 790-792; (c) Gunanathan, C.; Shimon, L. J.
W.; Milstein, D. Angew. Chem. Int. Ed. 2008, 47, 8861-8864; (d )
Gunanathan, C.; Shimon, L. J. W.; Milstein, D. J. Am. Chem. Soc.
2009, 131, 3146–3147; (e) Gnanaprakasam, B.; Balaraman, E.; Ben-
David, Y.; Milstein, D. Angew. Chem. Int. Ed. 2011, 50, 12240–12244; (f)
Balaraman, E.; Khaskin, E.; Leitus, G.; Milstein, D. Nat. Chem. 2013, 5,
122-125; (g) Khusnutdinova, J. R.; Ben-David, Y.; Milstein, D. J. Am.
Chem. Soc. 2014, 136, 2998−3001; (h) Fogler, E.; Garg, J.; Hu, P.; Leitus,
G.; Shimon, L. J. W.; Milstein, D. Chem. Eur. J. 2014, 20, 15727-15731. (i)
Gellrich, U; Khusnutdinova, J. R.; Leitus, G. M.; Milstein, D. J. Am.
Chem. Soc. 2015, 137, 4851−4859.
We believe that our findings contribute significantly to the
development of superior biofuel, based on long-chain alco-
hols, from ethanol. Experiments are underway aimed at fur-
ther mechanistic insight and improvements.
ASSOCIATED CONTENT
Supporting Information Available:
Experimental details –catalysts, kinetic plots, monitoring
experiments, spectra. This material is available free of charge
AUTHOR INFORMATION
Corresponding Author
Author Contributions
The manuscript was written through contributions of all
authors. / All authors have given approval to the final version
of the manuscript.
(11) (a) Zhang, J; Leitus, G; Ben-David, Y; Milstein, D. Angew.
Chem., Int. Ed. 2006, 45, 1113-1115; (b) Balaraman, E.; Gnanaprakasam,
B.; Shimon, L. J. W.; Milstein, D. J. Am. Chem. Soc. 2010, 132, 16756–
16758; (c) Balaraman, E; Ben-David, Y; Milstein, D. Angew. Chem., Int.
Ed. 2011, 50, 11702-11705.
ACKNOWLEDGMENT
This work was supported by the Israel Science Foundation
and by the Bernice and Peter Cohn Catalysis Research Fund.
D. M. holds the Israel Matz Professorial Chair of Organic
Chemistry. Y.X. thanks the Alternative Sustainable Energy
Research Initiative (AERI) of the Weizmann Institute for a
postdoctoral fellowship.
(12) For selected reviews see: Gunanathan, C.; Milstein, D. Science
2013, 341, 1229712; (b) Gunanathan, C.; Milstein, D. Chem. Rev. 2014,
114, 12024−12087
.
(13) For DFT calculations for the mechanism of aldehyde for-
mation, see: Ye, X.; Plessow, P. N.; Brinks, M. K.; Schelwies, M.;
Schaub, T.; Rominger, F.; Paciello, R.; Limbach, M.; Hofmann , P. J.
Am. Chem. Soc. 2014, 136, 5923−5929.
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