Ogata et al.
SCHEME 3. Two Plausible Reaction Pathways
SCHEME 4. Reduction of the (Z)-Alkenyl Methyl Sulfone
allation or Grignard-type carbonyl addition of 9 produces 8.
Marek et al. reported the formation of alkenylzirconium species
by the reaction of both (E)- and (Z)-alkenyl sulfones with
zirconocene(II)-olefin complexes and their subsequent reactions
2d with 1
1
9
with electrophiles. When (Z)-alkenyl methyl sulfone 2d was
treated with 1 at 0 °C for 5 min, the terminal olefin 12 was
produced in 20% yield with the saturated sulfone 13 (Scheme
4
). The yield of 12 increased with increasing reaction time.20
Deuteration of the organotitanium intermediate produced the
deuterated olefin d-12 and dideuterated sulfone d-13 (Scheme
5).
SCHEME 5. Formation of the Deuterio Olefin d-12 and the
Dideuterio Sulfone d-13
Although there is no decisive experimental evidence that
clarifies the mechanism for the formation of the trans-deuteriated
olefin d-12, the above results might support the alkenylationvia
the formation of the alkenyltitanium species 9 (path B). Such
alkenylation of alkynes and aldehydes with the alkenyltitanium
species generated by the tertiary alkylation of titanium vinyl-
21
carbene complexes was reported by us. Indeed, the conjugated
diene 5j was obtained in good yields by the reaction of 3a with
(18) For the reactions via titanacycles, see: (a) Suzuki, D.; Urabe, H.;
(
E)-configuration in good yields (Table 3). Treatment of the
Sato, F. J. Am. Chem. Soc. 2001, 123, 7925. (b) Suzuki, D.; Tanaka, R.;
Urabe, H.; Sato, F. J. Am. Chem. Soc. 2002, 124, 3518. (c) Tanaka, R.;
Nakano, Y.; Suzuki, D.; Urabe, H.; Sato, F. J. Am. Chem. Soc. 2002, 124,
R,â-unsaturated ketone 4o with 2c also formed the R-alkenyl
allylic alcohol 6r with complete stereoselectivity (entry 9,
9682. (d) Mitsui, K.; Sato, T.; Urabe, H.; Sato, F. Angew. Chem., Int. Ed.
Table 3).
2004, 43, 490. (e) Tanaka, R.; Yuza, A.; Watai, Y.; Suzuki, D.; Takayama,
Y.; Sato, F.; Urabe, H. J. Am. Chem. Soc. 2005, 127, 7774. For the reactions
via zirconacycles, see: (f) Takahashi, T.; Tsai, F.; Kotora, M. J. Am. Chem.
Soc. 2000, 122, 4994. (g) Takahashi, T. Pure Appl. Chem. 2001, 73, 271.
(h) Takahashi, T.; Ishikawa, M.; Huo, S. J. Am. Chem. Soc. 2002, 124,
Reaction Pathway. As we described in the previous paper,7
the titanocene(II)-promoted cross-coupling of unsaturated com-
pounds is expected to proceed via the formation of five-
membered titanacycles (path A in Scheme 3). Compounds 2
react with unsaturated compounds 3 or 4 in the presence of 1
to form two titanacycle intermediates 7a and 7b, which exist
in equilibrium. The subsequent elimination of the methylsulfonyl
group via 7b produces the dienyltitaniums or titanium alkoxides
of allylic alcohols 8 that produce the conjugated dienes 5 or
allylic alcohols 6 upon hydrolysis. Similar reactions via the
formation of five-membered titana- and zirconacycles from
divalent metal species and unsaturated compounds have been
388. (i) Takahashi, T.; Li, Y.; Stepnicka, P.; Kitamura, M.; Liu, Y.;
Nakajima, K.; Kotora, M. J. Am. Chem. Soc. 2002, 124, 576. (j) Takahashi,
T.; Li, Y.; Ito, T.; Xu, F.; Nakajima, K.; Liu, Y. J. Am. Chem. Soc. 2002,
124, 1144. (k) Takahashi, T.; Tsai, F.; Li, Y.; Wang, H.; Kondo, Y.;
Yamamoto, M.; Nakajima, K.; Kotora, M. J. Am. Chem. Soc. 2002, 124,
5
059. (l) Zhou, X.; Li, Z.; Wang, H.; Kitamura, M.; Kanno, K.; Nakajima,
K.; Takahashi, T. J. Org. Chem. 2004, 69, 4559.
(19) (a) Farhat, S.; Marek, I. Angew. Chem., Int. Ed. 2002, 41, 1410. (b)
Chinkov, N.; Majumdar, S.; Marek. I. J. Am. Chem. Soc. 2002, 124, 10282.
(
2
2
c) Chinkov, N.; Chechik, H.; Majumdar, S.; Liard, A.; Marek, I. Synthesis
002, 2473. (d) Chinkov, N.; Majumdar, S.; Marek. I. J. Am. Chem. Soc.
003, 125, 13258. (e) Chinkov, N.; Sklute, G.; Chechik, H.; Abramovitch,
investigated and employed for diene-, enyne-, and diyne-
A.; Amsallem, D.; Varghese, J.; Majumdar, S.; Marek, I. Pure Appl. Chem.
2004, 76, 517. (f) Farhat, S.; Zouev, I.; Marek, I. Tetrahedron 2004, 60,
intramolecular couplings17 and for one-pot synthesis of aromatic
1
329. (g) Marek, I.; Chinkov, N.; Levin, A. Synlett 2006, 501.
and heteroaromatic compounds.1
8
(20) The reaction of 2d with 1 at 25 °C for 2 h formed 12 in a lower
An alternative pathway that involves the formation of
alkenyltitanium species 9 (path B) should also be considered.
Desulfurizative titanation of 2 with 1 via the π-complexes 10
or titanacyclopropanes 11 affords 9. The subsequent carbomet-
yield (36%) and also formed a substantial amount (27%) of a stereoisomeric
mixture of 1,1,8,8-tetraphenylocta-3,5-diene (15, Supporting Information),
which would be produced by titanocene(II)-promoted self-coupling of 2d.
(21) Takeda, T.; Saeki, N.; Takagi, Y.; Fujiwara, T. Chem. Lett. 2000,
1198.
3820 J. Org. Chem., Vol. 72, No. 10, 2007