LETTER
Catalytic Hydrosilylation of Carbonyl Compounds
255
(11) For compound 6, see: (a) Albano, V. G.; Bandini, M.;
Melucci, M.; Monari, M.; Piccinelli, F.; Tommasi, S.;
Umani-Ronchi, A. Adv. Synth. Catal. 2005, 347, 1507.
OH
Me
Me
OH
Me
Me
(b) Albano, V. G.; Bandini, M.; Barbarella, G.; Melucci, M.;
Monari, M.; Piccinelli, F.; Tommasi, S.; Umani-Ronchi, A.
Chem. Eur. J. 2006, 12, 667.
R
Me
8 R = H
9 R = MeO
99% [69% ee (S)]
97% [67% ee (S)]
10 63% [77% ee (S)]
(12) Typical Procedure for Hydrosilylation of Methyl
Biphenyl-4-yl Ketone (1)
OH
OH
Me
OH
Me
Zinc acetate (9.2 mg, 0.05 mmol; Wako 260-01881, lot
LTM1219) and the ketone (196 mg, 1.0 mmol) were placed
in a flask. Under an argon atmosphere, absolute THF (3.0
mL) was added at r.t. The mixture was stirred for 10 min at
65 °C, and (EtO)2MeSiH (320 mL, 2.0 mmol) was then
added by a syringe. The mixture was stirred for 24 h at
65 °C. The reaction was monitored by TLC examination; the
ketone was consumed, and the silyl ether product was
observed. At 0 °C, aq HCl (2 N, 2 mL) was added to quench
the reaction. After stirring for 1 h, the mixture was extracted
with EtOAc (3 × 10 mL), and the extract was washed with
brine and aq NaHCO3 and dried over Na2SO4. After
concentration, the residue was purified by silica gel column
chromatography (hexane–EtOAc as eluent) to give the
corresponding desired alcohol 2 (196 mg, 0.99 mmol) in
99%.
n-C5H11
11 98% [77% ee (S)]
12 98% [71% ee (S)]
13 95% [92% ee (S)]
Figure 1 Asymmetric reduction of several ketones
good to excellent, further experiments are now under way
to reach high efficiency.
Acknowledgment
This work was partly supported by a Grant-in-Aid for Scientific
Research from the Ministry of Education, Culture, Sports, Science
and Technology of Japan (Concerto Catalysts, 460:18065011), the
Japan Society for the Promotion of Science (18350049).
Asymmetric Hydrosilylation of Methyl a-Naphthyl
Ketone
Under the same reaction conditions above described in the
typical procedure, the ligand 7a (27.4 mg, 0.06 mmol) and
methyl a-naphthyl ketone (170 mg, 1.0 mmol) were used to
obtain the alcohol 13 (163 mg, 0.95 mmol) in 95% and 92%
ee (S); analysis, CHIRALCEL OJ-H [hexane–2-PrOH
(95:5), 0.8 mL min–1]; tR (S) = 34.2 min, tR (R) = 43.5 min.
(13) Preparation of Ligands 7a and 7b
References and Notes
(1) (a) Andersson, P. G.; Munslow, I. J. Modern Reduction
Methods; Wiley-VCH: New York, 2008. (b) Burke, S. D.;
Danheiser, R. L. Handbook of Reagents for Organic
Synthesis, Oxidizing and Reducing Agents; John Wiley and
Sons: Chichester, 1999.
(2) For reviews, see: (a) Bullock, R. M. Angew. Chem. Int. Ed.
2007, 46, 7360. (b) Enthaler, S.; Junge, K.; Beller, M.
Angew. Chem. Int. Ed. 2008, 47, 3317. (c) Riant, O.;
Mostefi, N.; Courmarcel, J. Synthesis 2004, 2943. (d) For
papers: Shaikh, N. S.; Enthaler, S.; Junge, K.; Beller, M.
Angew. Chem. Int. Ed. 2008, 47, 2497.
(3) (a) Mimoun, H. J. Org. Chem. 1999, 64, 2582. (b)Mimoun,
H.; de Saint Laumer, J. Y.; Giannini, K.; Scopelliti, R.;
Floriani, C. J. Am. Chem. Soc. 1999, 121, 6158.
(4) (a) Bette, V.; Mortrex, A.; Lehmann, C. W.; Carpentier,
J.-F. Chem. Commun. 2003, 332. (b) Bette, V.; Mortorex,
A.; Savoia, D.; Carpentier, J.-F. Tetrahedron 2004, 60,
2837.
(5) Mastranzo, V. M.; Quintero, K.; de Parrodi, C. A.; Juaristi,
E.; Walsh, P. J. Tetrahedron 2004, 60, 1781.
(6) Ushio, H.; Mikami, K. Tetrahedron Lett. 2005, 46, 2903.
(7) Gérard, S.; Pressel, Y.; Riant, O. Tetrahedron: Asymmetry
2005, 16, 1889.
A mixture of (1R,2R)-cyclohexane-1,2-diamine (116 mg,
1.0 mmol), 4-phenylthiophene-2-carbaldehyde (392 g, 2.1
mmol, commercially available), MgSO4 (2.4 g) in THF
(10 mL) was stirred at r.t. for 40 h. After diluted with EtOAc
(10 mL), the mixture was filtered through Celite and was
concentrated to give white solids (ca. 470 mg). A MeOH
solution (15 mL) of the solids was treated with NaBH4 (392
mg) at r.t. for 18 h. Then, H2O (15 mL) was added, and the
mixture was extracted with EtOAc. The extract was washed
with brine and dried over Na2SO4. After concentration, the
residue was purified by silica gel column chromatography
with hexane–EtOAc to give white solids (265 mg, 0.58
mmol) in 58% yield.
Compound 7a: mp 113–115 °C. IR (KBr): n = 3100, 3056,
2927, 2853, 1451, 737, 688 cm–1. 1H NMR (300 MHz,
CDCl3): d = 0.91–2.37 (m, 14 H), 3.90–3.94 (m, 2 H), 4.13–
4.18 (m, 2 H), 7.24–7.39 (m, 8 H), 7.54–7.57 (m, 4 H). 13
C
(75 MHz, CDCl3): d = 25.1, 31.6, 45.7, 60.4, 118.8, 123.4,
126.0, 126.7, 128.5, 135.8, 141.3, 145.7. Anal. Calcd (%) for
C28H30N2S2: C, 73.32; H, 6.59; N, 6.11. Found: C, 72.91; H,
6.69; N, 6.01; [a]D29 –17.0 (c 1.00, CHCl3).
(8) Bandini, M.; Melucci, M.; Piccinelli, F.; Sinisi, R.;
Tommasi, S.; Umani-Ronchi, A. Chem. Commun. 2007,
4519.
Synthesis of Compound 7b
Starting from 2,6-diisopropylaniline via 2,6-diisopropyl-
phenyliodide, 2,6-diisopropylphenyl boronic acid was
prepared. The mixture of the boronic acid (463 mg, 2.25
mmol), 4-bromothiophene-2-carbaldehyde (318 mg, 1.5
mmol, commercially available), Pd(OAc)2 (3.4 mg), S-Phos
(12.7 mg), K3PO4 (650 mg, 3.0 mmol) in toluene (3.0 mL) at
100 °C for 24 h. The mixture was diluted with EtOAc and
filtered through Celite. After concentration, the residue
was purified by silica gel column chromatography to give
4-(2¢,6¢-diisopropylphenyl)thiophene-2-carbaldehyde (354
mg, 1.3 mmol) in 87%. A mixture of (1R,2R)-cyclohexane-
1,2-diamine (46 mg, 0.4 mmol), thiophene-2-carbaldehyde
(9) Hydrosilylation of imines with chiral zinc catalysts:
(a) Ireland, T.; Fontanet, F.; Tchao, G.-G. Tetrahedron Lett.
2004, 45, 4383. (b) Park, B.-M.; Mun, S.; Yun, J. Adv.
Synth. Catal. 2006, 348, 1029.
(10) (a) Nishiyama, H.; Furuta, A. Chem. Commun. 2007, 760.
(b) Furuta, A.; Nishiyama, H. Tetrahedron Lett. 2008, 49,
110.
Synlett 2009, No. 2, 253–256 © Thieme Stuttgart · New York