O. I. Kolodiazhnyi et al. / Tetrahedron Letters 45 (2004) 6955–6957
6957
structures. Some physical characteristics are reported
below.
ment of the compound 6 with borane resulted in the
optically pure borane complex 7, which constitutes a
new chiral ligand.6 Compound 7 is stable to oxidation
and hydrolysis by air, can be kept without racemization,
and can be purified by column chromatography on silica
gel. The co-ordinated BH3 of complex 7 was removed on
treatment with diethylamine to give the diastereomeri-
cally pure tertiary phosphine 6. Compound 6 was oxi-
dized to the corresponding tertiary phosphine oxide 8,
which was isolated as crystalline product. The structure
and purity of compounds 6–8 have been confirmed by
elemental analysis and NMR spectroscopy.5
General procedure for the reaction of aldehyde 1a with
Ph2PSiMe3: To a solution of 1a (1.1mmol) in 5mL of THF
(or toluene) was added Ph2PSiMe3 (1.0mmol) at ꢁ20°C.
The solution was left at this temperature overnight. Then
the temperature was raised to +20°C and after 1h the
solvent was evaporated to give tertiary phosphine 3a. To a
solution of 3a in THF (3mL) was added a solution of
borane in THF (1.1mmol) at ꢁ20°C. The reaction mixture
was left at 0°C for 6–12h. The solvent was evaporated and
the residue was chromatographed on a silica gel column
(hexane–ethyl acetate = 6:1) to give 4a: Yield 80%. Rf 0.42
(hexane–ethyl acetate = 6:1). [a]D +41.6 (c 1.5, ethyl
1
acetate). H NMR (CDCl3), d, ppm (J, Hz): ꢁ0.16 (9H, s,
The configuration of the newly formed stereogenic cen-
ter of compounds 3–5 was determined to be S by NMR
SiMe3); 0.18–1.40 (3H, m, BH3); 1.25 [3H, s, (CH3)2C]; 1.33
[3H, s, (CH3)2C]; 3.23 [1H, dd J 8, J 1(CH2O)]; 3.43 [1H,
dd, J 7.5, J 1 (CH2O)]; 4.53 (1H, m, CHCH2O); 5.00 (1H,
dd, J 4.5, J < 1, PCH); 7.66 (6H, m, C6H5); 7.93 (4H, m,
C6H5). 31P NMR (CHCl3): dP 21.60ppm, d JPB 57Hz. The
borane complex 4a was dissolved in excess diethylamine
and left for 12h. The volatiles were evaporated in vacuum
and the residue was extracted with hexane, which was
3
spectroscopy, the large value of the JHH constant and
2
the small value of the JHP constant of compounds 3–
5 indicating the anti-conformation of the H–C1–C2–H
and O@P–C1–H bonds.7 The stereochemistry of this
reaction is probably kinetically controlled. Nucleophilic
attack of silylphosphines to the less shielded (Si) face of
the carbonyl group provides, preferentially, the (S)-3
diastereomer according to CramÕs rule.
20
filtered off under argon. 3a: ½aꢂD ꢁ7 (c 4, toluene). 1H NMR
(CDCl3), d, ppm (J, Hz): ꢁ0.02 (s, CH3Si); 1.33 (s, CH3);
4.33 (m, OCH2CH); 4.49 (m, OCH2CH); 4.72 (m,
CH2CHO); 4.99 (m, PCH); 7.50(m, C 6H5); 7.90(m,
C6H5). 31P NMR (CHCl3): dP ꢁ7.69; ꢁ10.62 ppm (ratio
ꢀ11:1). The tertiary phosphines 3b and 3c and the borane
complexes 4b and 4c were obtained analogously. 3b: 31P
NMR (toluene), ppm: dP 4.4. 4b: Yield 64%. Rf 0.35, [a]D
ꢁ71.8 (c 3, CHCl3). 31P NMR (CHCl3): dP 25.30ppm. 3c:
Yield 60%.31P NMR (toluene): dP ꢁ10.50; ꢁ11.30ppm
In conclusion, we have found that the reaction between
silylphosphines and chiral aldehydes proceeds with good
stereoselectivity to give addition products in high chem-
ical yields. The reaction can be applied to asymmetric
synthesis of new chiral organophosphorus compounds.
20
(ratio 9:1). 5a: mp 167°C (toluene), ½aꢂD +11 (c 2, CHCl3).
1H NMR (CDCl3), d, ppm (J, Hz): 1.17 (3H, s, Me2Ca);
1.20(3H, s, Me 2Cb); 3.88 (1H, d, J 2 CaH2); 3.897 (1H, d, J
1.5 CbH2); 4.39 (1H, dt, J 6.5, J 2 OCHCH2); 4.59 (1H, dd,
J 5, J 0.9, PCH); 4.40(1H, m, OH); 7.80(6H, m, 4H,
C6H5); 7.49 (4H, m, C6H5). 31P NMR (CHCl3): dP
Acknowledgement
Financial support for this work from the State Founda-
tion of Basic Researches of Ukraine (Project 03.07/
00047) is gratefully acknowledged.
20
30.87ppm. 5b: mp 156°C, ½aꢂD ꢁ59 (c 3, CHCl3). 31P
20
NMR (CHCl3): dP 32ppm. 5c: mp 121°C, ½aꢂD ꢁ30( c 2,
CHCl3). 31P NMR (CHCl3): dP 29.4ppm. The compounds
6 and 7 were prepared analogously to 3a and 4a. 6: 31P
NMR (CHCl3), ppm: dP ꢁ10.68. 7: Rf 0.37 (hexane–ethyl
References and notes
1. (a) Kolodiazhnyi, O. I. Tetrahedron: Asymmetry 1998, 9,
1279–1332; (b) Kolodiazhnyi, O. I. Advances in Asymmetric
Synthesis; Hassner, A., Ed.; JAI: Stamford-London, 1998;
Vol. 3, Chapter 5, pp 273–357, and references cited therein.
2. Hilderbrand, R. L.; Henderson, T. G. The Role of Phos-
phonates in Living Systems; CRC: Boca Raton, 1983; pp 5–
30.
3. Kolodiazhnyi, O. I. Tetrahedron 2003, 59, 5923–6018.
4. (a) Epstein, M.; Buckler, S. A. Tetrahedron 1962, 18,
1231–1242; (b) Petrov, K. A.; Parshina, V. A. Zh. Obshch.
Khim. 1961, 5, 3417; (c) Becker, G.; Mundt, O. Z. Anorg.
Allgem. Chem. 1980, 462, 130–142; (d) Kolodiazhnyi, O. I.
Tetrahedron Lett. 1982, 23, 4933–4936.
20
acetate 3:1). ½aꢂD +23.6 (c 3, CHCl3). 1H NMR (CDCl3), d,
ppm: ꢁ0.17 (9H, s, SiMe3); ꢁ0.20 (9H, s, SiMe3); 0.60–1.30
[3H, m, BH3); 1.11 [3H, s, (CH3)2C]; 1.20[3H, s, (CH 3)2C];
1.33 [3H, s, (CH3)2C]; 1.36 [3H, s, (CH3)2C]; 4.59 (1H, m,
CHCHCH2); 4.53 (1H, m, CHCHCH2); 3.64 (1H, dt,
OCH2); 3.77 (1H, dt, OCH2); 3.90(1H, dt, OCH 2); 4.11
(1H, dt, OCH2); 5.16 (1H, dd, J 9, J < 1, PCH); 7.20(3H,
m, C6H5); 7.80(2H, m, C 6H5). 31P NMR (CHCl3): dP
27.40ppm.
6. Studies of compounds 6–8 as ligands in transition metal
complexes are currently in progress.
7. Hanaya, Y.; Miyoshi, A.; Nogushi, A.; Kawamoto, H.;
Armour, M.-A.; Hogg, A. M.; Yamamoto, H. Bull. Chem.
Soc. Jpn. 1990, 63, 3590–3594.
5. All new compounds shown in Schemes 1–3 gave satisfac-
tory analytical data and NMR spectra consistent with their