2
complexes can form some h -ketone complexes, 11, (metalla-
15. Thus, although 5 cannot be isolated, it is present as the first
intermediate in the reaction before the nucleophilic attack on the
carbonyl moiety occurs as described originally in Scheme 3.
In conclusion, the synthesis of exo-methylene-cyclopentane
and -cyclobutane has been achieved in a one-pot sequence from
oxiranes)13 which can further insert into an alkyne moiety to
give the same oxatitanacyclopentene derivatives 6. This
mechanism was already reported for the reaction of d-ynones
5 5 2 3 2
with [(C H ) Ti(PMe ) ] to form 3-bis(cyclopentadienyl)-
14
2
2
-oxa-3-titanabicyclo[3.3.0]oct-4-ene in good overall yield.
readily available starting material with diisopropoxy(h -pro-
Although the intramolecular addition to a substituted alkyne to
form the unsaturated oxatitanacycle worked well, here again the
reaction on a terminal alkyne gives a low isolated yield (35%)
of the cyclic product after hydrolysis, as described in Scheme
pene)titanium. The mechanism of this reaction has been
investigated and is composed by a carbometalation reaction of
the monosubstituted-unactivated alkyne followed by intra-
molecular nucleophilic acyl substitution.
4.
I. M. is a Ygal Alon fellow. This research was supported in
part by The Israel Science Foundation founded by The
Academy of Sciences and Humanities (No. 060-471) and by the
fund for the promotion of research at the Technion. Acknow-
ledgement is also made to the donors of The Petroleum
Research Fund, administered by the ACS, for partial support of
this research (PRF#33747-AC1).
Notes and references
1
2
3
K. Harada, H. Urabe and F. Sato, Tetrahedron Lett., 1995, 36, 3203.
C. Averbuj, J. Kaftanov and I. Marek, Synlett, 1999, 1939.
O. G. Kulinkovitch, A. I. Savchenko, S. V. Sviridov and D. A.
Vasilevski, Mendeleev Commun., 1993, 230.
Scheme 4
4
C. M. Williams, V. Chaplinski, P. R. Schreiner and A. de Meijere,
Tetrahedron Lett., 1998, 39, 7695.
So, in order to check if the first step of the reaction of 1 with
or 4 was a reaction at the alkynyl (Scheme 3) or at the carbonyl
centers (Scheme 4), we decided to investigate the behavior of 1
with cyclohexanone as described in Scheme 5.
3
5 R. Mizojiri, H. Urabe and F. Sato, Tetrahedron Lett., 1999, 40, 2557.
6 K. L. Lee, S. I. Kim and J. K. Cha, J. Org. Chem., 1998, 63, 9135.
7 For pertinent references on the intramolecular nucleophilic acyl
substitution, see: S. Okamoto, A. Kasatkin, P. K. Zubaidha and F. Sato,
J. Am. Chem. Soc., 1996, 118, 2208.
4
Treatment of 1 eq. of Ti(OiPr) with 2 eq. of iPrMgX in the
presence of 1 eq. of cyclohexanone leads to two products, 12
and 13, in a respectively 5 to 1 ratio and in quantitative yields.
The major product 12 results from the reaction of diisopro-
8
A. Kasatkin and F. Sato, Tetrahedron Lett., 1995, 36, 6079; A. Kasatkin,
K. Kobayashi, S. Okamoto and F. Sato, Tetrahedron Lett., 1996, 37,
1
3
849; R. Mizojiri, H. Urabe and F. Sato, Angew. Chem., Int. Ed., 1998,
7, 2666.
2
poxy(h -propene)titanium 1 with the carbonyl moiety which
can further react with iodine to give 14 whereas 13 is formed
from the direct attack of the Grignard reagent on the
cyclohexanone.15 No trace of cyclohexanol was detected after
hydrolysis in the crude reaction mixture which clearly indicates
that the reaction does not proceed through the oxametallacycle
9
O. G. Kulinkovich, S. V. Sviridov, T. S. Vasilevski and T. S. Pritskaya,
Zh. Org. Khim., 1989, 25, 2245; O. G. Kulinkovich and T. S. Pritskaya,
J. Org. Chem. USSR (Engl. Transl.), 1990, 25, 2027; O. G.
Kulinkovitch, S. V. Sviridov and D. A. Vasilevski, Synthesis, 1991, 234;
J. Lee, J. D. Ha and J. K. Cha, J. Am. Chem. Soc., 1997, 119, 8127; J.
Lee and J. K. Cha, J. Org. Chem., 1997, 62, 1584; S. Y. Cho, J. Lee,
R. K. Lammi and J. K. Cha, J. Org. Chem., 1997, 62, 8235; V.
Chaplinski and A. de Meijere, Angew. Chem., Int. Ed. Engl., 1995, 34,
2
1
545; V. Chaplinski, H. Winsel, M. Kordes and A. de Meijere, Synlett,
997, 111; C. M. Williams and A. de Meijere, J. Chem. Soc., Perkin
Trans. 1, 1998, 3699.
1
1
1
1
0 I. Marek and J. F. Normant, Carbometalation reactions in Metal-
catalyzed Cross-coupling Reactions, ed. F. Diederich and P. J. Stang,
Wiley-VCH, 1998, 271.
1 E.-I. Negishi, S. J. Holmes, J. M. Tour, J. A. Miller, F. E. Cederbaum,
D. R. Swanson and T. Takahashi, J. Am. Chem. Soc., 1989, 111,
3
336.
2 The synthesis of a 6-membered ring was also performed successfully
but for unknown reasons, the expected product was not stable during the
purification by chromatography.
3 G. Erker and F. Rosenfeldt, J. Organomet. Chem., 1982, 224, 29; R. M.
Waymouth, K. R. Clauser and R. H. Grubbs, J. Am. Chem. Soc., 1986,
1
08, 6385; G. Fachinetti, C. Birani, C. Floriani, A. Chiesi-Villa and C.
Guastini, J. Am. Chem. Soc., 1978, 100, 1921; E.-I. Negishi and T.
Takahashi, Bull. Chem. Soc. Jpn., 1998, 71, 755.
1
1
4 D. F. Hewlett and R. J. Whitby, J. Chem. Soc., Chem. Commun., 1990,
1
684.
5 The fact that iPrMgX reacts faster with Ti(OiPr)
4
than with a ketone has
been successfully used for the synthesis of functionalized alkynyl
titanium derivatives: N. Morlender-Vais, J. Kaftanov and I. Marek,
Synthesis, 2000, 917.
Scheme 5
1850
Chem. Commun., 2000, 1849–1850