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Table 2 Evaluation of 1a in RCM and CMa
proved highly efficient for very challenging substrates, including
in enyne metathesis. 1a was also shown active and selective in
cross-metathesis. In addition to these attractive features, 1a,
bearing a phosphite, is potentially more economically viable than
its congener G-II which bears tricyclohexylphosphine.13 Because
of such remarkable catalytic activity and lower production costs,
this new family of catalysts shows great promise. Studies aimed at
addressing synthetic and mechanistic issues of this NHC/P(OR)3
synergy are ongoing in our laboratories.
Pre-catalyst
(mol%)
Entry Substrate
1
Product
Yield (%)b
1a (0.025)
98 (97)
89
G-II (0.025)
2
1a (0.05)
1a (0.2)
1a (0.05)
1a (0.1)
99 (89)
78 (76)
97 (91)
499 (94)
The authors gratefully acknowledge the EaStCHEM School
of Chemistry and the EC (CP-FP 211468-2 EUMET) for
funding this project, and the EPSRC National Mass Spectro-
metry Centre (Swansea) for carrying out mass analyses.
3
4
5
6
Notes and references
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´
(b) R. H. Grubbs, P. L. Burk and D. D. Carr, J. Am. Chem. Soc.,
1975, 97, 3265; (c) R. R. Schrock, S. Rockluge, J. Wengrovius,
G. Rupprecht and J. Fellmann, J. Mol. Catal., 1980, 8, 73.
2 (a) R. H. Grubbs, in Handbook of Metathesis, Wiley-VCH, Weinheim,
vol. 1–3, 2003; (b) D. Astruc, New J. Chem., 2005, 29, 42;
(c) P. H. Deshmukh and S. Blechert, Dalton Trans., 2007, 2479;
(d) A. H. Hoveyda and A. R. Zhugralin, Nature, 2007, 450, 243.
3 (a) S. T. Nguyen, L. K. Johnson, R. H. Grubbs and J. W. Ziller,
J. Am. Chem. Soc., 1992, 114, 3974; (b) P. Schwab, M. B. France,
J. W. Ziller and R. H. Grubbs, Angew. Chem., Int. Ed. Engl., 1995,
34, 2039.
1a (0.025)
95 (91)
91
G-II (0.025)
7
8
1a (0.075)
1a (2)
96 (94)
63 (62)
4 (a) J. Huang, E. D. Stevens, J. L. Petersen and S. P. Nolan, J. Am.
Chem. Soc., 1999, 121, 2674; (b) M. Scholl, T. M. Trnka,
J. P. Morgan and R. H. Grubbs, Tetrahedron Lett., 1999, 40,
2247; (c) L. Ackermann, A. Furstner, T. Weskamp, F. J. Kohl and
¨
9
1a (5)
86 (86)
98 (91)
99 (78)
W. A. Herrmann, Tetrahedron Lett., 1999, 40, 4787;
(d) C. Samojlowicz, M. Bieniek and K. Grela, Chem. Rev., 2009,
109, 3708; (e) G. C. Vougioukalakis and R. H. Grubbs, Chem.
Rev., 2010, 110, 1746.
5 X. Bantreil, T. E. Schmid, R. A. M. Randall, A. M. Z. Slawin and
C. S. J. Cazin, Chem. Commun., 2010, 46, 7115.
6 (a) R. B. Bedford, C. S. J. Cazin and S. L. Hazelwood, Angew. Chem.,
Int. Ed., 2002, 41, 4120; (b) R. B. Bedford, S. L. Hazelwood and
M. E. Limmert, Chem. Commun., 2002, 2610; (c) C.-Y. Ho and
T. F. Jamison, Angew. Chem., Int. Ed., 2007, 46, 782; (d) O. Diebolt,
10
1a (0.05)
1a (0.1)
11
12
1a (5)
92 (87)
81
V. Jurcık, R. C. da Costa, P. Braunstein, L. Cavallo, S. P. Nolan, A.
´
G-II (5)
M. Z. Slawin and C. S. J. Cazin, Organometallics, 2010, 29, 1443.
7 (a) M. Gatti, L. Vieille-Petit, X. Luan, R. Mariz, E. Drinkel,
A. Linden and R. Dorta, J. Am. Chem. Soc., 2009, 131, 9498;
(b) K. M. Kuhn, T. M. Champagne, S. H. Hong, W.-H. Wei,
A. Nickel, C. W. Lee, S. C. Virgil, R. H. Grubbs and
R. L. Pederson, Org. Lett., 2010, 12, 984; (c) V. Sashuk,
L. H. Peeck and H. Plenio, Chem. Eur. J., 2010, 16, 3983;
(d) L. H. Peeck and H. Plenio, Organometallics, 2010, 29, 2761;
(e) X. Bantreil, R. A. M. Randall, A. M. Z. Slawin and S. P. Nolan,
Organometallics, 2010, 29, 3007.
8 M. S. Sanford, J. A. Love and R. H. Grubbs, Organometallics,
2001, 20, 5314.
9 X. Bantreil, A. Poater, C. A. Urbina-Blanco, A. M. Z. Slawin,
L. Cavallo, C. S. J. Cazin, manuscript in preparation.
10 J. A. Love, M. S. Sanford, M. W. Day and R. H. Grubbs, J. Am.
Chem. Soc., 2003, 125, 10103.
75 (72)
[420 : 1]d
72
1a (0.2)
13c
G-II (0.2)
91 (83)
[420 : 1]d
14c
1a (0.5)
a
Reaction conditions: substrate (0.25 mmol), pre-catalyst, MTBE
b
(0.5 mL), 50 1C, 8 h. Isolated yields in parentheses; average of at
least two runs. Methyl acrylate (5 equiv.) as coupling partner.
c
d
1
E/Z ratios in brackets determined by H NMR.
tested in olefin metathesis. This represents, to the best of our
knowledge, the first example of P(OR)3-containing ruthenium
benzylidene complexes fully characterised and shown efficient in
olefin metathesis reactions. Complex 1a, featuring a P(OiPr)3
ligand, proved superior to its PCy3 and P(OEt)3 analogues, in
particular for challenging substrates. 1a is efficient for RCM
reactions using catalyst loadings as low as 0.025 mol%, and
11 (a) S. P. Nolan and C. D. Hoff, J. Organomet. Chem., 1985, 290,
365; (b) S. A. Serron, E. D. Stevens, N. L. Jones, P. J. Fagan and
S. P. Nolan, Organometallics, 1996, 15, 5209.
12 J. Broggi, C. A. Urbina-Blanco, H. Clavier, A. Leitgeb,
C. Slugovc, A. M. Z. Slawin and S. P. Nolan, Chem.–Eur. J.,
2010, 16, 9215.
13 PCy3 is ca. 40 times more expensive than P(OiPr)3.
c
7062 Chem. Commun., 2011, 47, 7060–7062
This journal is The Royal Society of Chemistry 2011