542
Bull. Chem. Soc. Jpn. Vol. 87, No. 4 (2014)
Rh-Catalyzed Asymmetric Hydrogenation
1H NMR spectrum and Elemental analysis data were
obtained after purification.
References
a) G.-H. Chu, M. Gu, J. A. Cassel, S. Belanger, T. M.
1
1H NMR (CDCl3): ¤ 2.50-2.61 (m, 1H), 2.69-2.79 (m, 1H),
3.72 (s, 3H), 3.73-3.85 (m, 1H), 4.26 (dd, J = 9.0 and 6.0 Hz,
1H), 4.75 (t, J = 9.0 Hz, 1H), 4.86 (s, 1H), 6.30-6.35 (m, 2H),
6.95-7.00 (m, 1H). MS m/z 209 (M + H)+. Anal. Calcd for
C11H12O4: C, 63.45; H, 5.81%. Found: C, 63.49; H, 5.81%.
(S)-(6-Hydroxy-2,3-dihydrobenzofuran-3-yl)acetic Acid
(2b). To a solution of (6-hydroxy-1-benzofuran-3-yl)acetic
acid (1b) (1.92 g, 10 mmol), NaOMe (0.27 g, 5 mmol) in meth-
anol (35 mL) in a glass autoclave was added a solution of 1,1¤-
bis((2S,4S)-2,4-diethylphosphotano)ferrocene (3k, 44 mg, 0.1
mmol) and [Rh(cod)2]OTf (47 mg, 0.1 mmol, s/c = 100) in
methanol (15 mL) by cannula. Hydrogen (0.7 MPa) was intro-
duced, and the reaction mixture was stirred at room temper-
ature. After 2 h, enantiomeric excess (90%) and chemical yield
(quantitative) were determined by HPLC analysis using racemic
compound of 2b as the external standard. (CHIRALPAK AD-H,
eluted with n-hexane/ethanol/trifluoroacetic acid = 900/100/1
(v/v/v); flow rate, 1.0 mL min¹1; detection, 220 nm; room tem-
perature). The reaction mixture was concentrated. The residue
was diluted with water and 1 M aqueous HCl solution and
extracted with AcOEt. The extract was washed with brine,
dried over anhydrous Na2SO4, and concentrated. The residue
was purified by silica gel column chromatography (AcOEt:
hexane = 35:65 and then 100:0) to afford 2b (1.76 g, 91%) as a
slightly yellow solid.
Graczyk, R. N. DeHaven, N. Conway-James, M. Koblish, P. J.
Santini, S. P. Sahoo, J. P. Berger, K. L. MacNaul, G. Zhou, A.
Agrawal, R. Alvaro, T.-a. Cai, M. Hernandez, S. D. Wright, D. E.
c) P. Diaz, S. S. Phatak, J. Xu, F. R. Fronczek, F. Astruc-Diaz,
C. M. Thompson, C. N. Cavasotto, M. Naguib, ChemMedChem
e) F. Xu, Y. Zhang, J. Wang, J. Pang, C. Huang, X. Wu, Z. She,
Tripathi, A. K. Yadav, A. Ajay, S. S. Bisht, V. Chaturvedi, S. K.
2
a) N. Negoro, S. Sasaki, S. Mikami, M. Ito, M. Suzuki, Y.
Tsujihata, R. Ito, A. Harada, K. Takeuchi, N. Suzuki, J. Miyazaki,
T. Santou, T. Odani, N. Kanzaki, M. Funami, T. Tanaka, A.
Tsujihata, R. Ito, M. Suzuki, K. Takeuchi, N. Suzuki, J. Miyazaki,
T. Santou, T. Odani, N. Kanzaki, M. Funami, T. Tanaka, T.
S. Sasaki, S. Mikami, M. Ito, Y. Tsujihata, R. Ito, M. Suzuki, K.
Takeuchi, N. Suzuki, J. Miyazaki, T. Santou, T. Odani, N. Kanzaki,
M. Funami, A. Morohashi, M. Nonaka, S. Matsunaga, T. Yasuma,
1H NMR (DMSO-d6): ¤ 2.39-2.49 (m, 1H), 2.61-2.71 (m,
1H), 3.56-3.68 (m, 1H), 4.14 (dd, J = 9.0, 6.8 Hz, 1H), 4.64
(t, J = 9.0 Hz, 1H), 6.15 (d, J = 2.2 Hz, 1H), 6.23 (dd, J = 8.0,
2.2 Hz, 1H), 6.98 (dd, J = 8.0, 0.7 Hz, 1H), 9.27 (br s, 1H),
12.33 (br s, 1H).
3
a) T. Ohta, T. Miyake, N. Seido, H. Kumobayashi, H.
5194. e) N. Ortega, S. Urban, B. Beiring, F. Glorius, Angew.
Anal. Calcd for C10H10O4¢0.2H2O: C, 60.73; H, 5.30%.
Found: C, 60.84; H, 5.35%.
Gram-Scale Synthesis of (S)-(6-Hydroxy-2,3-dihydroben-
zofuran-3-yl)acetic Acid (2b). To a solution of (6-hydroxy-1-
benzofuran-3-yl) acetic acid (1b) (26.9 g, 140 mmol), NaOMe
(3.8 g, 70 mmol) in methanol (500 mL) in a glass autoclave was
added a solution of 1,1¤-bis((2S,4S)-2,4-diethylphosphotano)-
ferrocene (3k, 620 mg, 1.4 mmol) and [Rh(cod)2]OTf (656 mg,
1.4 mmol, s/c = 100) in methanol (200 mL) by cannula.
Hydrogen (0.7 MPa) was introduced, and the reaction mixture
was stirred at room temperature. After 2 h, enantiomeric excess
(90%) and chemical yield (quantitative) were determined by
HPLC analysis using racemic 2b as the external standard.
4
a) R. Noyori, Asymmetric Catalysis in Organic Synthesis,
John Wiley & Sons, New York, 1993. b) M. J. Burk, Acc. Chem.
Blaser, C. Malan, B. Pugin, F. Spindler, H. Steiner, M. Studer,
Curr. Opin. Drug Discovery Devel. 2003, 6, 855. g) X. Zhang,
Homogeneous Hydrogenation, ed. by J. G. de Vries, C. J. Elsevier,
Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, 2007.
doi:10.1002/9783527619382.
(CHIRALPAK AD-H, eluted with n-hexane/ethanol/trifluoro-
¹1
acetic acid = 900/100/1 (v/v/v); flow rate, 1.0 mL min
detection, 220 nm; room temperature).
;
5
6
a) A. Togni, C. Breutel, A. Schnyder, F. Spindler, H.
The reaction mixture was concentrated. The residue was
diluted with water and 1 M HCl aqueous solution and extracted
with AcOEt. The extract was washed with brine, dried over
anhydrous Na2SO4, and concentrated to afford 2b as a brown
solid (28.0 g, purity 99%, quantitative). The residue was used
for the next step without further purification.
Blaser, H.-P. Buser, H.-P. Jalett, B. Pugin, F. Spindler, Synlett
1999, 867. c) H.-U. Blaser, H.-P. Buser, R. Häusel, H.-P. Jalett, F.
Brieden, B. Pugin, F. Spindler, M. Studer, A. Togni, Top. Catal.
2002, 19, 3. e) H.-U. Blaser, B. Pugin, F. Spindler, M. Thommen,
Supporting Information
7
U. Berens, M. J. Burk, A. Gerlach, W. Hems, Angew.
a) M. J. Burk, F. Bienewald, S. Challenger, A. Derrick,
1H NMR spectra of compound 2a, 2b, and HPLC charts of
racemic compound of 2a, 2b. This material is available free of
8