conformationally flexible dienes 12 and 14 to 16- and
18-membered cycloalkenes 13 and 15, respectively. The
hydrogenation of compound 13 under standard conditions leads
to the macrocyclic musk exaltolide,14 which is used as a
valuable perfume ingredient. Disaccharide 17 is an advanced
intermediate en route to tricolorin A, a carcinostatic resin
glycoside isolated from Ipomoea tricolor.2d The examples
summarized in Table 2 clearly highlight the excellent compati-
bility of the allenylidene catalyst 5a with various functional
groups, including even unprotected secondary hydroxy
groups.
Although the mode of action of these new metathesis
catalysts and the nature of the actual intermediates involved in
the catalytic cycle require further indepth studies, we have
shown that the addition of an excess of PCy3 strongly retards the
metathetic conversion.
Current work in our laboratories is aiming at investigating the
mechanism as well as to further explore the preparative scope of
these readily accessible and highly promising metathesis
catalysts, since they allow substantial possible variations of
their basic structural motive.
Table 2 Ring closing metathesis employing Ru-allenylidene catalyst 5aa
Substrate
Product
Yield
(%)
Ts
N
75
40
N
Ts
8
9
O
O
O
O
O
O
10
11
O
O
O
O
90
The authors are grateful to Deutscher Akademischer Aus-
tauschdienst (DAAD) for a stipend to M. P., covering his stay in
Mu¨lheim for a three month period. We also thank K.
Langemann and T. Mu¨ller, Mu¨lheim, for providing various
starting materials.
12
13
O
O
NH
NH
Notes and References
73
† E-mail: pierre.dixneuf@univ-rennes1.fr
14
15
1 K. J. Ivin and J. C. Mol, Olefin Metathesis and Metathesis Polymeriza-
tion, Academic Press, New York, 1997; R. H. Grubbs, S. J. Miller and
G. C. Fu, Acc. Chem. Res., 1995, 28, 446; M. Schuster and S. Blechert,
Angew. Chem., Int. Ed. Engl., 1997, 36, 2036; A. Fu¨rstner, Top. Catal.,
1997, 4, 285; S. K. Armstrong, J. Chem. Soc., Perkin Trans. 1, 1998,
371.
2 (a) A. Fu¨rstner and K. Langemann, Synthesis, 1997, 792; (b) A. Fu¨rstner
and K. Langemann, J. Org. Chem. 1996, 61, 8746; (c) A. Fu¨rstner and
K. Langemann, J. Org. Chem., 1996, 61, 3942; (d) A. Fu¨rstner and T.
Mu¨ller, J. Org. Chem., 1998, 63, 424.
O
O
O
O
O
85
O
O
Ph
O
O
O
O
O
O
O
O
O
Ph
O
O
OH
O
3 S. T. Nguyen, R. H. Grubbs and J. W. Ziller, J. Am. Chem. Soc. 1993,
115, 9858; P. Schwab, M. B. France, J. W. Ziller and R. H. Grubbs,
Angew. Chem., Int. Ed. Engl. 1995, 34, 2039; E. L. Dias, S. T. Nguyen
and R. H. Grubbs, J. Am. Chem. Soc., 1997, 119, 3887.
OH
O
4 T. E. Wilhelm, T. R. Belderrain, S. N. Brown and R. H. Grubbs,
Organometallics, 1997, 16, 3867.
16
17
5 A ruthenium allenylidene intermediate has been suggested in the
catalytic coupling of propy-2-yn-1-ols with allylic alcohols, cf B. M.
Trost and J. A. Flygare, J. Am. Chem. Soc., 1992, 114, 5476.
6 M. A. Bennett and A. K. Smith, J. Chem. Soc., Dalton Trans., 1974,
233; R. A. Zelonka and M. C. Baird, Can. J. Chem. 1972, 50, 3063.
7 C. Bruneau and P. H. Dixneuf, Chem. Commun., 1997, 507.
a All reactions using 5a were carried out in toluene at 80 °C using a catalyst
loading of 5 mol%.
previous observations with ruthenium-based initiators,3,8,9 their
catalytic activity decreases in the order PCy3 > PPri3 >> PPh3
(Table 1). With 5a (2.5 mol%) as the catalyst, diene 6 is
quantitatively cyclized to dihydropyrrole 7 after 4 h in toluene
at 80 °C (entry 5). Dichloromethane can also be used, although
the turnover frequency of 5 is slightly lower in this particular
reaction medium at 40 °C (cf. entries 2 and 3).
Having established the optimum reaction conditions, we
applied catalyst 5a to RCM of a set of representative diene
substrates. As can be seen from the results compiled in Table 2,
this catalyst nicely applies to the formation of essentially all ring
sizes ! 5, including macrocyclic and medium sized products.
The isolated yields obtained were found to be good to excellent
and are comparable to those previously obtained using the
Grubbs carbenes 1 [9: 75% vs. (68%);12 13: 90% vs. (79%);2c
15: 73% vs. 83%;2a 17: 85% vs. 77%2d]. Only in the case of the
10-membered ring of jasmine ketolactone 11, did the allenyli-
dene complex 5a turn out to be somewhat less efficient [11:
40% vs. (86%)13].
8
A. W. Stumpf, E. Saive, A. Demonceau and A. F. Noels, J. Chem.,
Soc. Chem. Commun., 1995, 1127; A. Demonceau, A. W. Stumpf, E.
Saive and A. F. Noels, Macromolecules, 1997, 30, 3127.
9 A. Hafner, A. Mu¨hlebach and P. A. van der Schaaf, Angew. Chem., Int.
Ed. Engl., 1997, 36, 2121.
10 P. H. Dixneuf and C. Bruneau, in Organic Synthesis via Organome-
tallics, OSM 5, ed. G. Helmchen, Vieweg, Wiesbaden, 1997, p. 1; D.
Pe´ron, A. Romero and P. H. Dixneuf, Organometallics, 1995, 14,
3319.
11 D. Pilette, L. Ouzzine, H. Le Bozec, P. H. Dixneuf, C. E. F. Rickard and
W. R. Roper, Organometallics, 1992, 11, 809.
12 M. S. Visser, N. M. Heron, M. T. Didiuk, J. F. Sagal and A. H. Hoveyda,
J. Am. Chem. Soc., 1996, 118, 4291.
13 A. Fu¨rstner and T. Mu¨ller, Synlett, 1997, 1010.
14 Exaltolide is a trademark of Firmenich SA, Geneva, Switzerland; for a
general review see: G. Ohloff, Riechstoffe und Geruchssinn, Springer,
Berlin, 1990.
Received in Cambridge, UK, 1st May 1998; 8/03286F
1316
Chem. Commun., 1998