H. Ito et al. / Tetrahedron 68 (2012) 3423e3427
3427
spectra. Tetramethylsilane (1H) and CDCl3
(
13C) were employed as
include MOL file and InChiKey of the most important compound
internal and external standards, respectively. Mesitylene was used
as the internal standard for determining yields using the NMR data.
Gas chromatographic (GLC) analyses were conducted on a Shi-
madzu GC-2014 equipped with a flame ionization detector. HPLC
analyses were carried out using a Hitachi Elite LaChrome HPLC
system with an L-2400 UV detector. High-resolution mass spectra
were recorded on a JEOL JMS-T100GC mass spectrometer. All
compounds in this paper are known compounds besides [(E)-3a].
The 1H and 13C NMR of allylboronates were identical with those
previously reported.5a,b A potassium tert-butoxide solution of tet-
rahydrofuran (1.0 M) was purchased from SigmaeAldrich Co.
(328650-50ML) and used as received.
described in this article.
References and notes
1. (a) Hoffmann, R. W. In Stereocontrolled Organic Synthesis; Trost, B. M., Ed.;
Blackwell Scientific Publications: Oxford, 1994; pp 259e274; (b) Matteson, D. S.
Stereodirected Synthesis with Organoboranes; Springer: Berlin, 1995; (c) Roush,
W. R. Stereoselective synthesis In Methods in Organic Chemistry E21b; Ahlbrecht,
H., Helmchean, G., Arend, M., Herrmann, R., Eds.; Georg Thieme: Stuttgart,
1995; pp 1410e1485.
2. For selected examples of optically active allylboronates with a chiral auxiality
on the boron center, see: (a) Hoffmann, R. W. Pure Appl. Chem. 1988, 60, 123; (b)
Hoffmann, R. W.; Niel, G.; Schlapbach, A. Pure Appl. Chem. 1990, 62, 1993; (c)
Matteson, D. S. Tetrahedron 1998, 54, 10555; (d) Pietruszka, J.; Schone, N. Angew.
Chem., Int. Ed. 2003, 42, 5638; (e) Fang, G.; Aggarwal, V. Angew. Chem., Int. Ed.
2007, 46, 359; (f) Roush, W. R.; Walts, A. E.; Hoong, L. K. J. Am. Chem. Soc. 1985,
107, 8186.
4.1.1. (E)-4,4,5,5-Tetramethyl-2-(6-phenylhex-3-en-2-yl)-1,3,2-
dioxaborolane [(E)-3a]. Into a reaction vial, bis(pinacolato)diboron
(254 mg, 1.0 mmol), copper(I) chloride (2.5 mg, 0.025 mmol), and
Xantphos(14.5mg, 0.025mmol)wereplaced.Afterthevialwassealed
with a septum, the vial was evacuated and filled with nitrogen gas
using a vacuum line through a needle. A THF solution of K(O-t-Bu)
(1.0 M, 0.50 mL, 0.50 mmol) and THF (0.5 mL) were added to the vial.
After stirring for 30 min, the reaction mixture was added by allylic
carbonate (E)-1a (117.1 mg, 0.5 mmol). The yields and selectivities
were determined from GC analysis of the crude solution. After com-
pletion of the reaction, the reaction mixture was passed through
a short path column (SiO2) with an eluent (ethyl acetate/hexane
30:70) and the solvents were removed under reduced pressure with
a rotary evaporator. The crude mixture was purified by flash chro-
matography (SiO2, ethyl acetate/hexane 0.3:99.7) to give the desired
3. (a) Ito, H.; Yamanaka, H.; Tateiwa, J.; Hosomi, A. Tetrahedron Lett. 2000, 41,
6821; (b) Takahashi, K.; Takagi, J.; Ishiyama, T.; Miyaura, N. Chem. Lett. 2000, 29,
982; (c) Takahashi, K.; Ishiyama, T.; Miyaura, N. J. Organomet. Chem. 2001, 625,
47.
4. For selected examples of the copper(I)-catalyzed reaction of
a,b-carbonyl
compounds with diboron, see: (a) Mun, S.; Lee, J.; Yun, J. Org. Lett. 2006, 8,
4887; (b) Lee, J.; Yun, J. Angew. Chem., Int. Ed. 2008, 47, 145; (c) Bonet, A.; Lillo,
V.; Ramirez, J.; Diaz-Requejo, M.; Fernandez, E. Org. Biomol. Chem. 2009, 7, 1533;
(d) Chea, H.; Sim, H.; Yun, J. Adv. Synth. Catal. 2009, 351, 855; (e) Chen, I.-H.; Yin,
L.; Itano, W.; Kanai, M.; Shibasaki, M. J. Am. Chem. Soc. 2009, 131, 11664; (f) Feng,
X.; Yun, J. Chem. Commun. 2009, 6577; (g) Sim, H.; Feng, X.; Yun, J. Chem.dEur. J.
2009, 15, 1939; (h) Chen, I.-H.; Kanai, M.; Shibasaki, M. Org. Lett. 2010, 12, 4098;
(i) Feng, X.; Yun, J. Chem.dEur. J. 2010, 16, 13609.
5. For our copper(I)/diboron catalysis for allylboronate synthesis, see: (a) Ito, H.;
Kawakami, C.; Sawamura, M. J. Am. Chem. Soc. 2005, 127, 16034; (b) Ito, H.; Ito,
S.; Sasaki, Y.; Matsuura, K.; Sawamura, M. J. Am. Chem. Soc. 2007, 129, 14856; (c)
Ito, H.; Kunii, S.; Sawamura, M. Nature Chem. 2010, 2, 972.
6. For copper(I)/diboron catalysis for allylboronate synthesis reported by other
groups, see: (a) Ramachandran, P. V.; Pratihar, D.; Biswas, D.; Srivastava, A.;
Reddy, M. V. R. Org. Lett. 2004, 6, 481; (b) Guzman-Martinez, A.; Hoveyda, A. J.
Am. Chem. Soc. 2010, 132, 10634; (c) Park, J. K.; Lackey, H. H.; Ondrusek, B. A.;
McQuade, D. T. J. Am. Chem. Soc. 2011, 133, 2410 See also Refs. 3b and c.
7. For other copper(I)/diboron catalysis reported by us, see: (a) Ito, H.; Kosaka, Y.;
Nonoyama, K.; Sasaki, Y.; Sawamura, M. Angew. Chem., Int. Ed. 2008, 47, 7424;
(b) Ito, H.; Sasaki, Y.; Sawamura, M. J. Am. Chem. Soc. 2008, 130, 15774; (c) Ito,
H.; Okura, T.; Matsuura, K.; Sawamura, M. Angew. Chem., Int. Ed. 2010, 49, 560;
(d) Ito, H.; Toyoda, T.; Sawamura, M. J. Am. Chem. Soc. 2010, 132, 5990; (e)
Zhong, C.; Kunii, S.; Kosaka, Y.; Sawamura, M.; Ito, H. J. Am. Chem. Soc. 2010,
132, 11440.
8. Tsuda, T.; Hashimoto, T.; Saegusa, T. J. Am. Chem. Soc. 1972, 94, 658.
9. In Ref. 5a, we reported that a substrate similar to 1a was consumed within 3 h
in a 1.0 M substrate concentration in the presence of the same catalyst loading
(5.0 mol %). It is reasonable that because of a lower concentration reported in
(0.5 M) Table 1, a longer reaction time was required (24 h).
product(E)-3aasacolorlessoil;1HNMR(400MHz, CDCl3):
d7.13e7.27
(m, 5H), 5.50e5.56 (m, 1H), 5.35e5.45 (m, 1H), 2.65 (t, J¼8.0 Hz, 2H),
2.30 (q, J¼7.6 Hz, 2H), 1.82 (qn, J¼7.2 Hz, 1H), 1.22 (s, 12H), 1.05 (d,
J¼9.7 Hz, 3H). 13C NMR (100 MHz, CDCl3):
d 142.19, 132.80, 128.41,
128.11, 127.35, 125.54, 82.95, 36.24, 34.56, 24.63, 24.56, 15.10.
HRMSeEI (m/z): [M]þ calcd for C18H27BO2, 286.2104; found, 286.2101.
4.1.2. (E)-4,4,5,5-Tetramethyl-2-(5-phenylpent-1-en-2-yl)-1,3,2-
dioxaborolane [(S)-3j]. The reaction was carried out with a chiral li-
gand (R,R)-QuinoxP* instead of Xantphos. 1H NMR (400 MHz, CDCl3):
d
7.14e7.28 (m, 5H), 5.78e5.87 (m,1H), 4.98e5.04 (m, 2H), 2.53e2.70
(m, 2H), 1.83e1.93 (m, 2H), 1.69e1.79 (m, 1H), 1.24 (s,12H). 13C NMR
(100 MHz, CDCl3): 142.6, 139.2, 128.5, 128.3, 125.6, 114.0, 83.2, 35.2,
10. Hoveyda and co-workers reported that use of excess NaOMe base (80 mol %) in
combination with copper(I) (5 mol %)/NHC ligand (6 mol %) leads to an im-
provement in reaction efficiency for the allylic boryl substitution as compared
to the reaction with 30 mol % NaOMe. They did not describe the reason for this
improvement effect. See Ref. 6b.
d
32.1, 29.9 (br, CeB), 24.7, 24.6. The ee value was determined by HPLC
analysis of the 4-nitrobenzoylated derivative of the corresponding
alcohol after NaBO3$4H2O oxidation of this compound with a chiral
stationary phase (Chiralcel OD-3, 40 ꢀC, 2.0% 2-PrOH/hexane, 0.5 mL/
min, S isomer tR¼28.8 min, R isomer tR¼33.8 min).
11. NHC or phosphine-catalyzed borylation of
a,b-carbonyl compounds with di-
boron was reported to proceed without a copper(I) salt. (a) Lee, K.-S.; Zhugralin,
ꢁ
A. R.; Hoveyda, A. H. J. Am. Chem. Soc. 2009, 131, 7253; (b) Bonet, A.; Gulyas, H.;
ꢁ
Fernandez, E. Angew. Chem., Int. Ed. 2010, 49, 5130.
12. Unpublished result.
Acknowledgements
13. For the reaction mechanism of the copper(I)-catalyzed reaction of unsaturated
compounds, see: (a) Dang, L.; Zhao, H.; Lin, Z.; Marder, T. B. Organometallics
2007, 26, 2824; (b) Dang, L.; Lin, Z.; Marder, T. B. Organometallics 2008, 27, 4443.
14. Hoveyda and co-workers reported that a copper(II) salt, Cu(OTf)2, performs as
a good copper catalyst precursor in the borylation of allylic substrates. See Ref.
6b.
This study was supported by a Grant-in-Aid for Scientific Re-
search (B) (JSPS) and the PRESTO program (JST).
15. Recently, Santos and co-workers reported a very useful method for borylation
Supplementary data
of
a,b-unsaturated carbonyl compounds using bis(2-hydroxypropyl)amine as
the activator of diboron, see: (a) Gao, M.; Thorpe, S. B.; Santos, W. L. Org. Lett.
2009, 11, 3478; (b) Thorpe, S. B.; Guo, X.; Santos, W. L. Chem. Commun. 2011,
424.
Supplementary data associated with this article can be found in