evaporated in vacuo and 3 was obtained as a pale yellow oily liquid by
distillation at 55 °C and 1 mmHg (377 mg, 81%).
PPh3 dissociation induced by high temperature and concomitant
reaction of the phosphine with EDA. In fact, it is known that
EDA and PPh3 give in an equilibrium reaction the phosphazine
EtOCOCHN2NPPh3, and traces of this product were always
found in our reaction mixtures. Furthermore, solutions contain-
ing equimolar amounts of EDA and PPh3 and 1 as catalyst do
not show dinitrogen evolution at 65 °C. At 90 °C only traces of
diethyl maleate ( < 1%) are detected after 2 h reaction, the ylide
EtOCOCHNPPh3 being the major product present in solution.
As stated above, the indenyl complex 7 decomposes EDA at
a lower temperature (45 °C) then 1 (65 °C), and this result is
consistent with the kinetic studies of Gamasa et al.,8 who found
that complex 7 dissociates PPh3 an order of magnitude faster
Compounds 2–6 gave satisfactory analytical and spectroscopic (1H and
13C NMR and MS) data.
1 (a) M. P. Doyle, Chem. Rev., 1986, 86, 919; (b) H. Bock and H. P. Wolf,
J. Chem. Soc., Chem. Commun., 1990, 690; (c) J. P. Collman, E. Rose
and G. D. Venburg, J. Chem. Soc., Chem. Commun., 1993, 934; (d)
W. J. Seitz, A. K. Saha and M. M. Hossain, Organometallics, 1993, 12,
2604; (e) T. Ye and M. A. McKervey, Chem. Rev., 1994, 94, 1091; (f)
A. Demonceau, C. A. Lemoine, A. F. Noels, I. T. Chizhevsky and
P. V. Sorok`ın, Tetrahedron Lett., 1995, 36, 8419; (g) M. P. Doyle, in
Comprehensive Organometallic Chemistry II, ed. L. S. Hegedus,
Pergamon Press, New York, 1995, vol. 12, ch. 5.1 and 5.2; (h)
M. P. Doyle, A. V. Kalinin and D. G. Ene, J. Am. Chem. Soc., 1996, 118,
8837; (i) A. F. Noels and A. Demonceau, in Applied Homogeneous
Catalysis by Organometallic Complexes, ed. B. Cornil and W. A.
Herrmann, Verlag Chemie, Weinheim, Germany, 1996.
2 H. Nishiyama, Y. Itoh, H. Matsumoto, S.-B. Park and K. Itoh, J. Am.
Chem. Soc., 1994, 116, 2223; P. Schwab, M. B. France, J. W. Ziller and
R. H. Grubbs, Angew. Chem., Int. Ed. Engl., 1995, 34, 2039.
3 A. Padwa and D. J. Austin, Angew. Chem., Int. Ed. Engl., 1994, 33,
1797; M. P. Doyle, C. S. Peterson, Q.-L. Zhou and H. Nishiyama, Chem.
Commun., 1997, 211; M. P. Doyle and M. A. McKervey, Chem.
Commun., 1997, 983.
4 The synthesis of cis-enediones have been previously described through
oxidative opening of furans: P. D. Williams and E. LeGoff, Tetrahedron
Lett., 1985, 26, 1367; C. Dom`ınquez, A. G. Csa´ky and J. Plumet,
Tetrahedron Lett., 1990, 31, 7669; B. M. Adger, C. Barrett, J. Brennan,
M. A. McKervey and R. W. Murray, J. Chem. Soc., Chem. Commun.,
1991, 1553.
5 L. K. Woo and D. A. Smith, Organometallics, 1992, 11, 2344.
6 B. M. Trost, G. Dyker and R. J. Kulawiec, J. Am. Chem. Soc., 1990, 112,
7809; B. M. Trost and R. J. Kulawiec, J. Am. Chem. Soc., 1992, 114,
5579; B. M. Trost and J. A. Flygare, J. Am. Chem. Soc., 1992, 114, 5476;
B. M. Trost, R. J. Kulawiec and A. Hammes, Tetrahedron Lett., 1993,
34, 587; B. M. Trost and J. A. Flygare, J. Org. Chem., 1994, 59, 1078;
B. M. Trost and J. A. Flygare, Tetrahedron Lett., 1994, 35, 4059.
7 Y. Kayama, M. Oda and Y. Kitahara, Chem. Lett., 1974, 345.
8 M. P. Gamasa, J. Gimeno, C. Gonzalez-Bernardo, B. M. Martin-Vaca,
D. Monti and M. Bassetti, Organometallics, 1996, 15, 302.
9 T. Braun, O. Gevert and H. Werner, J. Am. Chem. Soc., 1995, 117,
7291.
5
than 1 to form [RuCl(h -ligand)(PPh3)].
In the proposed catalytic cycle a neutral RuII cyclopenta-
dienyl carbene complex is involved, which is similar to
5
[RuCl(h -C5H5)(CPh2)(PPh3)], recently reported by Braun
et al.9 The high stereoselectivity observed for the nucleophilic
attack of the a-diazo carbonyl compound on the coordinated
carbene is probably related to the preferred orientation of the
carbene moiety caused by the cyclopentadienyl ligand.10
5
Furthermore, the steric constraint of the RuCl(h -C5H5)(PPh3)
fragment may favour the formation of the less sterically
demanding cis alkene.11
The extension of this research towards the synthesis of
unsymmetrical cis-enediones by using two different a-diazo-
carbonyl compounds is in progress. In particular, decomposi-
tion of a 1:1 mixture of EDA and N2CHCOMe yields 2, 3 and
cis-EtOCOCHNCHCOMe in ca. 1:1:3 molar ratio, respec-
tively. The double coupling between carbene units derived from
mono- and a,w-bis-diazo carbonyl compounds is also under
investigation and seems to give promising results.
This work was supported by the Italian Ministero dell’U-
niversita` e della Ricerca Scientifica e Tecnologica (Rome). The
authors thank Professor Giancarlo Verardo of the Dipartimento
di Scienze e Tecnologie Chimiche, Universita` di Udine, for
recording the mass spectra.
10 B. E. R. Schilling, R. Hoffmann and J. W. Faller, J. Am. Chem. Soc.,
1979, 101, 592; V. C. Gibson, Angew. Chem., Int. Ed. Engl., 1994, 33,
1565.
11 G. G. A. Balavoine, T. Boyer and C. Livage, Organometallics, 1992, 11,
456.
Footnotes and References
* E-mail: inorg@dstc.uniud.it
† The typical procedure adopted for the synthesis of cis-enediones 2–6 is
described here in detail for 3. A solution of 1-diazopropan-2-one (700 mg,
8.33 mmol) in 5 ml of toluene was added dropwise to a solution of 1 (6 mg;
8 mmol) in 10 ml of toluene, at 65 °C under Ar atmosphere. The solvent was
Received in Cambridge, UK, 4th September 1997; 7/06459D
2164
Chem. Commun., 1997