Chemistry Letters 2000
777
nC4H9, which was prepared from the corresponding dibro-
moalkene and 1-hexynylzinc chloride by the Pd-catalyzed cross-
coupling in 67% yield, was completely inert to the Pd-catalyzed
butatriene formation reaction with 2m.
References and Notes
1
"The Chemistry of Ketenes, Allenes, and Related Compounds," ed.
by S. Patai, Wiley, New York (1980).
a) H.-F. Chow, X.-P. Cao, and M.-K. Leung, J. Chem. Soc., Chem.
Commun., 2121 (1994), and references cited therein. b) H.-F. Chow,
X.-P. Cao, and M.-K. Leung, J. Chem. Soc., Perkin Trans. 1, 193
(1995). c) R. W. Saalfrank, A. Welch, and M. Haubner, Angew.
Chem., Int. Ed. Engl., 34, 2709 (1995).
2
3
a) Y. Wakatsuki, H. Yamazaki, N. Kumegawa, T. Satoh, and J. Y.
Satoh, J. Am. Chem. Soc., 113, 9604 (1991). b) Y. Wakatsuki, H.
Yamazaki, N. Kumegawa, and P. S. Johar, Bull. Chem. Soc. Jpn., 66,
987 (1993). c) Y. Wakatsuki, N. Koga, H. Yamazaki, and K.
Morokuma, J. Am. Chem. Soc., 116, 8105 (1994). d) C. S. Yi and N.
Liu, Organometallics, 15, 3968 (1996). e) Y. Suzuki, R. Hirotani, H.
Komatsu, and H. Yamazaki, Chem. Lett., 1299 (1999). f) T. Ohmura,
S. Yorozuya, Y. Yamamoto, and N. Miyaura, Organometallics, 19,
365 (2000).
4
5
M. Ogasawara, H. Ikeda, and T. Hayashi, Angew. Chem., Int. Ed.
Engl., 39, 1042 (2000).
a) F. Ramirez, N. B. Desai, and N. McKelvie, J. Am. Chem. Soc., 84,
1745 (1962). b) E. J. Corey and P. L. Fuchs, Tetrahedron Lett., 13,
3769 (1972).
6
Palladium-catalyzed selective substitutions of one of the two halides
from 1,1-dihalo-1-alkene have been reported. See, a) A. Minato, K.
Suzuki, and K. Tamao, J. Am. Chem. Soc., 109, 1257 (1987). b) J.
Uenishi, R. Kawahama, O. Yonemitsu, and J. Tsuji, J. Org. Chem.,
61, 5716 (1996). c) J. Uenishi, R. Kawahama, Y. Shiga, O.
Yonemitsu, and J. Tsuji, Tetrahedron Lett., 37, 6759 (1996).
a) dpbp = 2,2'-bis(diphenylphosphino)-1,1'-biphenyl. b) M.
Ogasawara, K. Yoshida, and T. Hayashi, Organometallics, 19, 1567
(2000), and references cited therein.
7
8
The assignment of the E- and Z-isomers was made by comparison of
The reaction is very sensitive to nucleophiles 2: while 1c
reacted with 2m to give 3cm in 73% yield, the closely related
nucleophile 2p was completely inert under the same reaction
condition and unreacted 1c was recovered from the reaction mix-
ture (entries 3 and 9). Because the nucleophilic center in 2m is
more hindered than that in 2p, the higher reactivity of 2m in the
reaction cannot be accounted for by the steric factors. The
unusual reactivity was double-checked by an independent experi-
ment. An equimolar mixture of 1c, 2m, and 2p was reacted for
22 h in THF at 35 °C in the presence of 5 mol% of the Pd–dpbp
catalyst, and 3cm was obtained with E/Z = 60/40 selectivity as a
sole butatriene product.10 The corresponding butatriene from 1c
and 2p was not detected at all by NMR and GC–MS analyses. In
the reactions with more basic nucleophiles, such as 2q or
Grignard reagents, dehydrobromination from 1 was a dominant
reaction giving conjugated diyne as main products (entry 10).
The reaction reported here can be regarded as a skeletal
rearrangement of the conjugated enynes to the butatriene frame-
works. Considering ca. 20 kcal/mol energy difference between
1,4-dimethylbutatriene and the corresponding enynes,3a the repre-
sented reaction is very unique and the difference of bond energy
between C–Br and C–Nu must be mainly contributory to the for-
mation of the butatrienes. Since the butatrienes obtained here
keep some energy in their skeletons, they must be reactive mole-
cules, and thus their application to further organic transforma-
tions will be an interesting subject.
1
5JHH values of the olefinic protons.9 3am: H NMR (CDCl3, 23 °C):
δ 1.67 (s, 3H of Z-isomer), 1.78 (s, 3H of E-isomer), 3.78 (s, 6H of Z-
5
isomer), 3.79 (s, 6H of E-isomer), 6.12 (d, J = 7.7 Hz, 1H of E-iso-
5
5
mer), 6.19 (d, J = 7.3 Hz, 1H of Z-isomer), 6.55 (d, J = 7.7 Hz, 1H
of E-isomer), 6.58 (d, 5J = 7.3 Hz, 1H of Z-isomer), 7.24–7.28 (m, 1H
of both isomers), 7.31–7.36 (m, 2H of both isomers), 7.41–7.44 (m,
2H of both isomers). 3bm: 1H NMR (CDCl3, 23 °C): δ 1.72 (s, 3H of
Z-isomer), 1.80 (s, 3H of E-isomer), 3.79 (s, 6H of Z-isomer), 3.80 (s,
6H of E-isomer), 6.19 (d, 5J = 7.8 Hz, 1H of E-isomer), 6.25 (d, 5J =
5
7.5 Hz, 1H of Z-isomer), 7.29 (d, J = 7.8 Hz, 1H of E-isomer), 7.32
(d, 5J = 7.5 Hz, 1H of Z-isomer), 7.45–7.58 (m, 3H of both isomers),
7.73–7.75 (m, 1H of both isomers), 7.78–7.81 (m, 1H of both iso-
mers), 7.85–7.87 (m, 1H of both isomers), 8.35–8.37 (m, 1H of both
isomers). 3cm: 1H NMR (CDCl3, 23 °C): δ 1.68 (s, 3H of Z-isomer),
5
1.77 (s, 3H of E-isomer), 3.79 (s, 6H of both isomers), 6.25 (d, J =
5
7.6 Hz, 1H of E-isomer), 6.33 (d, J = 7.3 Hz, 1H of Z-isomer), 6.57
5
5
(d, J = 7.6 Hz, 1H of E-isomer), 6.60 (d, J = 7.3 Hz, 1H of Z-iso-
mer), 7.50–7.54 (m, 2H of both isomers), 7.57–7.61 (m, 2H of both
isomers). 3dm: 1H NMR (CDCl3, 23 °C): δ 1.66 (s, 3H of Z-isomer),
1.76 (s, 3H of E-isomer), 3.78 (s, 6H of both isomers), 3.82 (s, 3H of
Z-isomer), 3.83 (s, 3H of E-isomer), 6.01 (d, 5J = 7.7 Hz, 1H of E-iso-
5
5
mer), 6.08 (d, J = 7.2 Hz, 1H of Z-isomer), 6.50 (d, J = 7.7 Hz, 1H
of E-isomer), 6.53 (d, 5J = 7.2 Hz, 1H of Z-isomer), 6.86–6.89 (m, 2H
of both isomers), 7.35–7.38 (m, 2H of both isomers). 3cn: H NMR
1
(CDCl3, 23 °C): δ 1.30 (t, J = 7.1 Hz, 3H of Z-isomer), 1.31 (t, J = 7.1
Hz, 3H of E-isomer), 1.60 (s, 3H of Z-isomer), 1.68 (s, 3H of E-iso-
mer), 2.25 (s, 3H of Z-isomer), 2.26 (s, 3H of E-isomer), 4.25–4.30
5
(m, 2H of both isomers), 6.30 (d, J = 7.7 Hz, 1H of E-isomer), 6.37
5
5
(d, J = 7.3 Hz, 1H of Z-isomer), 6.57 (d, J = 7.7 Hz, 1H of E-iso-
mer), 6.59 (d, 5J = 7.3 Hz, 1H of Z-isomer), 7.51–7.53 (m, 2H of both
isomers), 7.57–7.62 (m, 2H of both isomers).
9
a) Although it was claimed previously that the E-isomer should have
5
a larger JHH value than that of the corresponding Z-isomer,9b others
5
Judging from similarity between this reaction and the allene
synthesis,4 a probable intermediate of the Pd-catalyzed reaction is
a π-allenylpalladium species. Establishment of the intermediate
will be our next goal.
reported that JHH values of Z- and E-isomers of corresponding buta-
trienes were almost identical.9c We could detect the slight, but mean-
5
ingful differences between the JHH values of the two isomers of the
obtained butatrienes using high-resolution NMR technique (at 500
MHz with 0.076 Hz of digital resolution). b) R. Mantione, A. Alves,
P. P. Montijn, G. A. Wildschut, H. J. T. Bos, and L. Brandsma, Rec.
Trav. Chim. Pays-Bas, 89, 97 (1970). c) P. J. Bauer, O. Exner, R.
Ruzziconi, T. D. An, C. Tarchini, and M. Schlosser, Tetrahedron, 50,
1707 (1994).
This work was supported by "Research for the Future"
Program (the Japan Society for the Promotion of Science), a
Grant-in-Aid for Scientific Research (the Ministry of Education,
Science, Sports and Cullture, Japan), and Mitsubishi Chemical
Corporation Fund (to M. O.).
10 The yield of 3cm of this experiment is 34%, which is much lower
than that of Entry 1 in Table 1. This negative effect of 2p is unex-
pected and cannot be explained at this moment.