LETTER
(S)-4-Benzyl-1,3-oxazolan-3-ylmethyl(diphenyl)phos-
Chiral Phosphine Oxazolidine Ligands
1333
d = 7.64–7.11 (m, 15 H), 5.02 (d, 1 H, J = 3.84 Hz), 4.41 (d,
1 H, J = 3.84 Hz), 4.17 (dd, 1 H, J1 = 7.82 Hz, J2 = 7.30 Hz),
3.83 (dd, 1 H, J1 = 7.82 Hz, J2 = 7.30 Hz), 3.58–3.50 (m, 2
H). 3.25 (dd, 1 H, J1 = 14.76 Hz, J2 = 5.48 Hz); 13C NMR
(CDCl3, 100 MHz): d = 137.95–127.64 (m), 87.71, 72.66,
69.72 (d, J = 13.80 Hz), 52.26 (d, J = 87.20 Hz); 31P NMR
(CDCl3, 161.98 MHz): d = 29.95, LRMS: m/z (%) = 347
(2)(M+), 176 (100), 91 (62), 77 (33), 42 (89); Anal. Calcd for
C22H22NOP: C, 76.06; H, 6.38; N, 4.03. Found: C, 76.30; H,
6.31; N, 3.88.
phane (1a)
Mp 71–72 °C; [a]D20 +30 (c 0.7, CH2Cl2); 1H NMR (CDCl3,
400 MHz): d = 7.51–7.04 (m, 15 H), 4.47 (dd, 2 H, J1 = 7.76
Hz, J2 = 5.76 Hz), 3.85–3.82 (m, 1 H), 3.48 (d, 2 H, J = 7.00
Hz), 3.43–3.40 (m, 2 H), 2.79 (dd, 1 H, J1 = 13.70 Hz,
J2 = 5.88 Hz), 2.51 (dd, 1 H J1 = 13.70 Hz, J2 = 5.88 Hz); 13C
NMR (CDCl3, 100 MHz): d = 131.87–126.25 (m), 87.35 (d,
J = 6.30 Hz), 68.60, 61.08 (d, J = 9.60 Hz), 55.58 (d,
J = 87.80 Hz), 39.40; 31P NMR (CDCl3, 161.98 MHz):
d = 29.21; LRMS: m/z (%) = 361 (2, M+), 162 (100), 91 (50),
77 (67); Anal. Calcd for C23H24NOP: C, 76.43; H, 6.69; N,
3.88. Found: C, 76.19, H, 6.81; N 3.77.
(R)-4-Phenyl-1,3-oxazolan-3-ylethyl(diphenyl)phos-
phane (ent-1d)
Yield: 0.507 g (1.46 mmol, 73%); mp 108–109 ºC; [a]D
20
(S)-4-Isopropyl-1,3-oxazolan-3-ylethyl(diphenyl)phos-
phane (1b)
–90 (c 0.7, CH2Cl2); for the other spectral and analytical data
see 1d.
Yield: 0.439 g (1.40 mmol, 70%); mp 60–62 °C; [a]D20 +14
(c 0.7, CH2Cl2); 1H NMR (CDCl3, 400 MHz): d = 7.81–7.44
(m, 10 H), 4.58 (d, 1 H, J = 6.08 Hz), 4.39 (d, 1 H, J = 6.08
Hz), 3.88 (dd, 1 H, J1 = 8.24 Hz, J2 = 7.16 Hz), 3.57 (dd, 1
H, J1 = 16.00 Hz, J2 = 5.16 Hz), 3.45–3.37 (m, 2 H), 2.77–
2.72 (m, 1 H), 1.53–1.45 (m, 1 H), 0.71 (d, 3 H, J = 6.07 Hz),
0.69 (d, 3 H, J = 6.07 Hz); 13C NMR (CDCl3, 100 MHz):
d = 132.30–127.20 (m), 86.55 (d, J = 8.10 Hz), 72.45 (d,
J = 22.30 Hz), 66.06, 55.57 (d, J = 176.30 Hz), 30.04, 19.36,
17.56. 31P NMR (CDCl3, 161.98 MHz): d = 28.59; LRMS:
m/z (%) = 313 (2, M+), 128 (100), 84 (19), 77 (14), 69 (14),
55 (13), 42 (51); Anal. Calcd for C19H24NOP: C, 72.82; H,
7.72; N, 4.47. Found: C, 72.57; H, 7.85; N 4.22.
(9) Leutenegger, U.; Umbricht, G.; Fahrni, C.; von Matt, P.;
Pfaltz, A. Tetrahedron 1992, 48, 2143.
(10) For examples of monodentate ligands in palladium-
catalyzed asymmetric allylic alkylation see: (a) Dai, X.;
Virgil, S. Tetrahedron Lett. 1999, 40, 1245. (b) Fuji, K.;
Ohnishi, H.; Moriyama, S.; Tanaka, K.; Kawabata, T.;
Tsubaki, K. Synlett 2000, 351. (c) Gavrilov, K. N.;
Polosukhin, A. I.; Bondarev, O. G.; Lyubimov, S. E.;
Lyssenko, K. A.; Petrovskii, P. V.; Davankov, V. A. J. Mol.
Cat. A: Chem. 2003, 196, 39. (d) Dai, W.-M.; Yim, K. K.
Y.; Leung, W. H.; Haynes, R. K. Tetrahedron: Asymmetry
2003, 14, 2821.
(11) General Procedure for the Asymmetric Allylic
Alkylation: A THF (1 mL) solution of [Pd(h3-C3H5)Cl]2 (1
mg, 0.025 mmol, 2.5 mol%), catalyst 1a–d (10 mol%) was
stirred for 30 min under an argon atmosphere and then 1,3-
diphenyl-2-propenyl acetate (0.252 g, 1.0 mmol) was added.
The mixture was stirred for 10 min and a solution of sodium
dimethyl malonate, prepared from dimethyl malonate (0.264
g, 2.0 mmol) and sodium hydride (0.036 g, 1.5 mmol) in
THF (3 mL), was added at room temperature. The reaction
mixture was then stirred for the time specified in Table 1, at
room temperature. After this time, saturated NH4Cl was
added and it was extracted with CH2Cl2 (3 ꢀ 15 mL) and the
combined organic layers were dried with MgSO4. The
solvent was evaporated and the crude product was purified
by flash chromatography eluting with hexane–EtOAc
(98:2). The enantiomeric excess of 4 was determined by 1H
NMR (CDCl3) analysis with chiral shift reagent Eu(hfc)3 and
the absolute configuration was determined by comparison of
the optical rotation.
(S)-4-Methyl-1,3-oxazolan-3-ylmethyl(diphenyl)phos-
phane (1c)
Yield: 0.325 g (1.14 mmol, 57%); bp 63–65 °C (0.30
mmHg); [a]D20 +9 (c 0.7, CH2Cl2); 1H NMR (CDCl3, 400
MHz): d = 7.47–6.94 (m, 10 H), 4.11 (d, 1 H, J = 5.04 Hz),
3.91 (d, 1 H, J = 5.04 Hz), 3.59–3.52 (m, 1 H), 3.18 (dd, 1 H,
J1 = 15.04 Hz, J2 = 7.42 Hz), 3.00 (dd, 1 H, J1 = 15.04 Hz,
J2 = 6.22 Hz), 3.05–2.71 (m, 2 H), 0.93 (d, 3 H, J = 6.22 Hz);
13C NMR (CDCl3, 100 MHz): d = 136.81–127.85 (m), 86.72
(d, J = 5.76 Hz), 70.11, 60.54 (d, J = 10.16 Hz), 53.82 (d,
J = 89.16 Hz), 15.05. 31P NMR (CDCl3, 161.98 MHz):
d = 29.32; LRMS: m/z (%) = 285 (2, M+), 100 (100), 77 (11),
70 (30), 42 (27), 28 (11); Anal. Calcd for C17H20NOP: C,
71.56; H, 7.06; N, 4.91. Found: C, 71.63, H, 6.90; N 4.77.
(S)-4-Phenyl-1,3-oxazolan-3-ylmethyl(diphenyl)phos-
phane (1d)
Yield: 0.493 g (1.42 mmol, 71%); mp 108–109 °C;
[a]D20 +90 (c 0.7, CH2Cl2); 1H NMR (CDCl3, 400 MHz):
Synlett 2005, No. 8, 1331–1333 © Thieme Stuttgart · New York