Table 3 Semihydrogenation of other (hetero)aromatic and aliphatic
alkynesa
under mild and base-free conditions tolerating several functional
groups.
Notes and references
1 J. Scheirs and D. B. Priddy, Modern Styrenic Polymers: Polystyrenes
and Styrenic Copolymers, John Wiley, Chichester, 2003.
2 J. Seayad, A. Tillack and M. Beller, Angew. Chem., Int. Ed., 2004,
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3 H.-J. Arpe, Industrial Organic Chemistry, Wiley-VCH, Weinheim,
2010.
Entry Substrate
1
Catalyst [mol%] Conv. [%] Yieldb [%]
0.75
499
96
4 F. Kerins and D. F. O’Shea, J. Org. Chem., 2002, 67, 4968.
5 (a) S. E. Denmark and C. R. Butler, J. Am. Chem. Soc., 2008,
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A. N. Ntepe and L. Ricard, J. Am. Chem. Soc., 2003, 125, 6070;
(c) R. F. Heck, Org. React., 1982, 27, 345.
2
3
1
499
499
0.75
2
2
6 H. Lindlar, Helv. Chim. Acta, 1952, 35, 446.
7 For reviews, see: (a) S. Gladiali and E. Alberico, Chem. Soc. Rev.,
4
5
0.75
1
499
499
97
96
2006, 35, 226; (b) J. S. M. Samec, J.-E. Backvall, P.-G. Andersson
¨
and P. Brandt, Chem. Soc. Rev., 2006, 35, 237.
8 H. S. La Pierre, J. Arnold and F. D. Toste, Angew. Chem., Int Ed.,
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6c
7
3
3
499
499
96
97
10 (a) M. A. Esteruelas, I. Gonzalez, J. Herrero and L. A. Oro,
´
a
Reaction conditions: 0.5 mmol substrate, catalyst (ratio 1 : 1):
Fe(BF4)2Á6H2O/PP3, 1 mL dry THF, 2 equiv. formic acid, 40 1C, 5 h.
J. Organomet. Chem., 1998, 551, 49; (b) R. R. Schrock and
J. A. Osborn, J. Am. Chem. Soc., 1976, 98, 4450.
11 M. A. Esteruelas, A. M. Lopez, L. A. Oro, A. Perez, M. Schulz and
H. Werner, Organometallics, 1993, 12, 1823.
b
Determined by GC using n-hexadecane as an internal standard.
3 equiv. formic acid.
c
12 C. Belger, N. M. Neisius and B. Plietker, Chem.–Eur. J., 2010,
16, 12214.
13 (a) K. Junge, K. Schroder and M. Beller, Chem. Commun., 2011,
¨
47, 4849; (b) C.-L. Sun, B.-J. Li and Z.-J. Shi, Chem. Rev., 2011,
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K. Junge and M. Beller, Angew. Chem., Int. Ed., 2008, 47, 3317;
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14 C. Bianchini, A. Meli, M. Peruzzini, P. Frediani, C. Bohanna,
M. A. Esteruelas and L. Oro, Organometallics, 1992, 11, 138.
15 For an iron-catalyzed hydrosilylation of internal alkynes, see:
(a) S. Enthaler, M. Harberberger and E. Irran, Chem.–Asian J.,
2011, 6, 1613; (b) S. C. Bart, E. Lobkovsky and P. J. Chirik, J. Am.
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16 For recent examples, see: (a) S. Zhou, S. Fleischer, K. Junge and
M. Beller, Angew. Chem., Int. Ed., 2011, 50, 5120; (b) K. M. Driller,
S. Prateeptongkum, R. Jackstell and M. Beller, Angew. Chem., Int.
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¨
X. Ribas, M. Costas and M. Beller, Angew. Chem., Int. Ed., 2011,
50, 1425; (d) C. Federsel, A. Boddien, R. Jackstell, R. Jennerjahn,
P. J. Dyson, R. Scopelitti, G. Laurenczy and M. Beller, Angew.
Chem., Int. Ed., 2010, 49, 9777; (e) K. Junge, B. Wendt, N. Shaikh
and M. Beller, Chem. Commun., 2010, 46, 1769; (f) A. Boddien,
F. Gartner, R. Jackstell, H. Junge, A. Spannenberg, W. Baumann,
¨
Scheme 1 Proposed catalytic cycle and experiments using deuterated
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(g) S. Prateeptongkum, K.-M. Driller, R. Jackstell and M. Beller,
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K. Junge, S. Das, D. Addis and M. Beller, Angew. Chem., Int.
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formic acid as reducing agent.
an inner-sphere hydrogenation mechanism. Additionally, the
deuterium is non-selectively distributed between the a- and
b-positions of the styrene. This result is in agreement with the
formation of an active iron dihydrido species [(HD)FeF(PP3)]+
from the corresponding formate complex by elimination of
carbon dioxide.17
17 G. Wienhofer, I. Sorribes, A. Boddien, F. Westerhaus, K. Junge,
¨
H. Junge, R. Llusar and M. Beller, J. Am. Chem. Soc., 2011, 133, 12875.
18 (a) P. O. Lagaditis, A. J. Lough and R. H. Morris, J. Am. Chem.
Soc., 2011, 133, 9662; (b) T. Ohkuma, M. Koizumi, K. Muniz,
G. Hilt, C. Kabuto and R. Noyori, J. Am. Chem. Soc., 2002,
124, 6508.
19 A. Boddien, D. Mellmann, F. Gartner, R. Jackstell, H. Junge,
¨
P. J. Dyson, G. Laurenczy, R. Ludwig and M. Beller, Science,
2011, 333, 1733.
In summary, we have developed the first iron-based catalytic
system for the selective transfer hydrogenation of alkynes.
Applying formic acid as a hydrogen donor a broad range of
aromatic and aliphatic terminal alkynes is selectively reduced
c
This journal is The Royal Society of Chemistry 2012
Chem. Commun., 2012, 48, 4827–4829 4829