Go Takahashi,a Eiji Shirakawa,*b Teruhisa Tsuchimotoa and
p-Tolylboronate 1a added to both electron-rich and -poor
aromatic aldehydes (entries 1 and 2). Benzaldehyde (2a) accepted
the addition of phenylboronates having a methoxy, trifluoro-
methyl, acetyl or hydroxymethyl group (entries 3–6). In contrast to
more nucleophilic arylmetals such as arylmagnesium halides
and aryllithiums, organoboronates are compatible with electro-
philic functional groups such as ketone and hydroxy. Hexanal,
an aliphatic aldehyde, also underwent the reaction with diverse
types of arylboronates to give a-pentylbenzyl alcohols with an
electron-donating or -withdrawing group at their para or meta
position (entries 7–11). Ketone moieties were unaffected,
showing a strong preference for aldehydes (entries 5 and 10).
For the addition of an alkenylboronate, 1-phenylpropyne was
found to be more effective than 4-octyne as an additive, affording
an increased yield of the corresponding allylic alcohol (entries
12 and 13).
Yusuke Kawakamia
aGraduate School of Materials Science, Japan Advanced Institute of
Science and Technology, Tatsunokuchi, Ishikawa, 923-1292, Japan
bDepartment of Chemistry, Graduate School of Science, Kyoto
University, Sakyo, Kyoto, 606-8502, Japan.
E-mail: shirakawa@kuchem.kyoto-u.ac.jp; Fax: 81 75 753 3988
Notes and references
1 For recent reviews, see: F. Alonso, I. P. Beletskaya and M. Yus, Chem.
Rev., 2004, 104, 3079–3159; M. Beller, J. Seayad, A. Tillack and H. Jiao,
Angew. Chem. Int. Ed., 2004, 43, 3368–3398.
2 For recent reviews, see: S. Saito and Y. Yamamoto, Chem. Rev., 2000,
100, 2901–2915; M. Rubin, A. W. Sromek and V. Gevorgyan, Synlett,
2003, 2265–2291.
3 For the palladium- or nickel-catalysed carbostannylation of alkynes, see:
E. Shirakawa, H. Yoshida, T. Kurahashi, Y. Nakao and T. Hiyama,
J. Am. Chem. Soc., 1998, 120, 2975–2976; E. Shirakawa, H. Yoshida,
Y. Nakao and T. Hiyama, J. Am. Chem. Soc., 1999, 121, 4290–4291;
E. Shirakawa, K. Yamasaki, H. Yoshida and T. Hiyama, J. Am. Chem.
Soc., 1999, 121, 10221–10222; E. Shirakawa, H. Yoshida, Y. Nakao and
T. Hiyama, Org. Lett., 2000, 2, 2209–2211; H. Yoshida, E. Shirakawa,
T. Kurahashi, Y. Nakao and T. Hiyama, Organometallics, 2000, 19,
5671–5678; E. Shirakawa, Y. Yamamoto, Y. Nakao, T. Tsuchimoto
and T. Hiyama, Chem. Commun., 2001, 1926–1927; H. Yoshida,
E. Shirakawa, Y. Nakao, Y. Honda and T. Hiyama, Bull. Chem. Soc.
Jpn., 2001, 74, 637–647.
Use of water as a solvent should be favorable for environmental
and safety reasons.15 Because H2O was found to be a crucial
activator in the addition (entries 5 and 6 of Table 1), we expected
that the reaction should be accelerated in the presence of a
substantial excess of the activator. Actually, the addition of 1a to
2a in water proceeded at a much lower temperature (40 uC, 2 h) to
afford 3a in 97% yield, though it required an excess amount
(1.5 equiv with respect to 2a) of 1a because of competitive
hydrolysis of 1a to toluene.16 Furthermore, glutaraldehyde (6),17
which is usually available only as an aqueous solution, successfully
reacted with organoboronates in a mixed solvent consisting of 1,4-
dioxane and H2O to provide diastereoisomeric mixtures18 of
lactols 7a or 7b (eqn. (2)).The lactols were easily oxidized to the
corresponding lactones 8a or 8b.19
4 For the nickel-catalysed addition of arylboron compounds to alkynes,
see: E. Shirakawa, G. Takahashi, T. Tsuchimoto and Y. Kawakami,
Chem. Commun., 2001, 2688–2689.
5 E. Oblinger and J. Montgomery, J. Am. Chem. Soc., 1997, 119,
9065–9066; X.-Q. Tang and J. Montgomery, J. Am. Chem. Soc., 1999,
121, 6098–6099; X.-Q. Tang and J. Montgomery, J. Am. Chem. Soc.,
2000, 122, 6950–6954; W.-S. Huang, J. Chan and T. F. Jamison, Org.
Lett., 2000, 2, 4221–4223; E. A. Colby and T. F. Jamison, J. Org.
Chem., 2003, 68, 156–166; K. M. Miller, W.-S. Huang and
T. F. Jamison, J. Am. Chem. Soc., 2003, 125, 3442–3443;
K. M. Miller, T. Luanphaisarnnont, C. Molinaro and T. F. Jamison,
J. Am. Chem. Soc., 2004, 126, 4130–4131.
6 The three-component coupling between phenylboronic acid, 1-phenyl-
propyne and an imine derived from benzaldehyde has been reported.
S. J. Patel and T. F. Jamison, Angew. Chem. Int. Ed., 2003, 42,
1364–1367.
7 To the best of our knowledge, there has been no report on the transition
metal-catalysed addition of organoboron compounds to aldehydes
except for the rhodium-catalysed reaction. M. Sakai, M. Ueda and
N. Miyaura, Angew. Chem. Int. Ed., 1998, 37, 3279–3281; M. Ueda
and N. Miyaura, J. Org. Chem., 2000, 65, 4450–4452; A. Fu¨rstner and
H. Krause, Adv. Synth. Catal., 2001, 343, 343–350; C. Moreau,
C. Hague, A. S. Weller and C. G. Frost, Tetrahedron Lett., 2001, 42,
6957–6960. See also ref. 9.
ð2Þ
8 Asymmetric addition of arylboronates to aromatic aldehydes mediated
by an excess amount of diethylzinc in the presence of a chiral
oxazolylalcohol has been reported. C. Bolm and J. Rudolph, J. Am.
Chem. Soc., 2002, 124, 14850–14851.
9 Addition products of triphenylborane to aldehydes were produced as
by-products (yield ¡ 22%) in the nickel-catalysed three-component
coupling between triphenylborane, isoprene and aldehydes. K. Shibata,
M. Kimura, K. Kojima, S. Tanaka and Y. Tamaru, J. Organomet.
Chem., 2001, 624, 348–353.
10 H2O has played a crucial role in the nickel-catalysed hydroarylation of
alkynes or 1,3-dienes using arylboronates. For alkynes, see ref. 4. For
1,3-dienes, see: E. Shirakawa, G. Takahashi, T. Tsuchimoto and
Y. Kawakami, Chem. Commun., 2002, 2210–2211.
11 Although the role of water is not clear at present, it may act as a Lewis
base that coordinates to the boron atom and promotes the attack of the
aryl groups on the aldehyde carbons.
12 Arylboronate 1a was found to be relatively stable to water, not being
hydrolysed on treatment of 1 equiv of H2O in 1,4-dioxane at 80 uC for
6 h.
In conclusion, we have disclosed that a catalytic amount of
alkynes in combination with a nickel catalyst promotes the
addition of organoboronates to aldehydes. Alkynes, one of the
most representative substrates in transition metal catalysis, do not
react with organoboron compounds or aldehydes but activate
them. Although the reaction mechanism including the role of the
alkynes is not clear at present, the complete inability of usual
ligands such as triphenylphosphine and 2,29-bipyridyl might imply
that the alkynes do not behave as conventional ligands.20,21 Studies
on the mechanistic details as well as application of the system to
other substrates are in progress.
13 p-Tolylboronic acid did not add to 2a at all under the conditions
identical to entry 6 in Table 1.
14 Yields of 4 and 5 were determined by isolation with SiO2
chromatography and 1H NMR, respectively.
We thank Professor Tamio Hayashi (Kyoto University) for
helpful discussions. This work was supported in part by Daicel
Chemical Industries, Ltd.
1460 | Chem. Commun., 2005, 1459–1461
This journal is ß The Royal Society of Chemistry 2005