M. Victor, L. N. Zakharov, A. L. Rheingold and F. Ja¨kle, J. Am. Chem.
Soc., 2006, 128, 16554.
alkenylborane 2s. (E)-Tamoxifen (5) was stereoselectively obtained
in 79% yield (E/Z = 97/3).20 Stereospecific iodination was
accomplished by treatment of the ammonia complex of 2s with
NIS, giving the alkenyl iodide 6 in 59% yield (E/Z = 96/4). An
oxidation reaction with trimethylamine N-oxide produced the
ketone 7 in 91% yield.
3 For recent advances of organoborane syntheses, see: (a) M. Suginome,
M. Shirakura and A. Yamamoto, J. Am. Chem. Soc., 2006, 128, 14438;
(b) J. M. Murphy, J. D. Lawrence, K. Kawamura, C. Incarvito and
J. F. Hartwig, J. Am. Chem. Soc., 2006, 128, 13684; (c) G. A. Molander
and N. Ellis, Acc. Chem. Res., 2007, 40, 275, and references therein.
4 E. Negishi, J. Organomet. Chem., 1976, 108, 281.
Installation of two aryl groups in juxtaposition across a boron-
substituted alkene is attractive in terms of the synthesis of boron-
containing p-conjugated materials. Thus, the reaction was
successfully applied to the construction of diboranyl compound
8 (eqn (4)).
5 (a) P. Binger and R. Ko¨ster, Tetrahedron Lett., 1965, 6, 1901; (b)
N. Miyaura, T. Yoshinari, M. Itoh and A. Suzuki, Tetrahedron Lett.,
1974, 15, 2961; (c) H. C. Brown, A. B. Levy and M. M. Midland, J. Am.
Chem. Soc., 1975, 97, 5017; (d) A. Pelter, C. R. Harrison,
C. Subrahmanyam and D. Kirkpatrick, J. Chem. Soc., Perkin Trans.
1, 1976, 2435.
6 (a) A. Pelter, T. W. Bentley, C. R. Harrison, C. Subrahmanyam and
R. J. Laub, J. Chem. Soc., Perkin Trans. 1, 1976, 2419; (b) A. Pelter,
K. J. Gould and C. R. Harrison, J. Chem. Soc., Perkin Trans. 1, 1976,
2428.
7 P. Binger, Angew. Chem., Int. Ed. Engl., 1967, 6, 84.
8 (a) Y. Chen, N.-S. Li and M.-Z. Deng, Tetrahedron Lett., 1990, 31,
2405; (b) Y. Chen, M.-Z. Deng and N. Shi, Chin. Sci. Bull., 1991, 36,
570.
ð4Þ
9 M.-Z. Deng, Y. Tang and W. Xu, Tetrahedron Lett., 1984, 25, 1797.
10 M. Naruse, K. Utimoto and H. Nozaki, Tetrahedron, 1974, 30, 3037.
11 P. Binger and R. Ko¨ster, J. Organomet. Chem., 1974, 73, 205.
12 J. Gerard and L. Hevesi, Tetrahedron, 2001, 57, 9109.
13 (a) P. Binger and R. Ko¨ster, Synthesis, 1973, 309; (b) J. Hooz and
R. Mortimer, Tetrahedron Lett., 1976, 17, 805.
14 The borate 1a, isolated as a solid, was prepared through cation exchange
from the corresponding lithium borate. The direct use of the lithium
borate generated in situ in THF also gave the product but in lower yield.
15 No reaction occurred in the absence of the palladium catalyst.
16 1-Alkynyldiorganyl(methoxy)borates undergo Sonogashira-type cross-
coupling reaction with aryl halides: (a) J. A. Soderquist, K. Matos,
A. Rane and J. Ramos, Tetrahedron Lett., 1995, 36, 2401; (b) A. Fu¨rstner
and G. Seidel, Tetrahedron, 1995, 51, 11165.
In summary, a new method for the stereoselective synthesis of
trisubstituted alkenylboranes has been developed, in which two
different aryl groups were installed across the carbon–carbon
double bond in a cis arrangement. Application of this method to
synthesis of boron-containing functional materials is under way.
This work was supported by Grant-in-Aid for Scientific
Research on Priority Areas 19027032 from Ministry of
Education, Culture, Sports, Science and Technology (MEXT).
N. I. thanks Research Fellowships of Japan Society for the
Promotion of Science for Young Scientists.
17 An alternative mechanism is also conceivable. The arylpalladium
bromide A acts as an electrophile such as alkyl halides, giving
diorganylpalladium D. Subsequent reductive elimination affords the
alkenylborane 2b and palladium(0).
Notes and references
1 (a) N. Miyaura, Top. Curr. Chem., 2002, 219, 11; (b) A. Suzuki and
H. C. Brown, Organic Synthesis via Boranes, Aldrich, Milwaukee, WI,
2003, vol. 3; (c) Boronic Acids, ed. D. G. Hall, Wiley-VCH, Weiheim,
Germany, 2005.
2 (a) N. Matsumi, K. Naka and Y. Chujo, J. Am. Chem. Soc., 1998, 120,
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18 G. Ko¨brich and H. R. Merkle, Angew. Chem., Int. Ed. Engl., 1967, 6, 74.
19 Other phenyl boronic esters including catecholate and ethylene glycolate
were also subjected to the reaction conditions. However, no desired
alkenylboronic esters were formed, presumably due to the instabilities of
the corresponding ‘ate’ complexes under the reaction conditions.
20 For stereoselective synthesis of (E)-Tamoxifen, see: (a) T. Stu¨demann,
M. Ibrahim-Ouali and P. Knochel, Tetrahedron, 1998, 54, 1299; (b)
K. Itami, T. Kamei and J. Yoshida, J. Am. Chem. Soc., 2003, 125,
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Chem. Commun., 2007, 4381–4383 | 4383