3.84. Found: C, 39.92; H, 4.16; N, 3.87.
1,3-Dichloro-2-propyl (S)-N-(1-phenylethyl)carbamate (6b). White needles, mp 69–72 °C (ethyl
acetate). 1H-NMR (CDCl3) δ 1.51 (3 H, d, J = 7.0, Me), 3.73 (2 H, d, J = 4.4, CH2Cl), 3.78 (2 H, d, J =
13
4.4, CH2Cl), 4.83 (1 H, m, MeCHPh), 5.07–5.11 (2 H, m, OCH and NH), 7.43 (5 H, m, Ph). C-NMR
(CDCl3) δ: 22.2 (q, Me), 32.6 (t, CH2Cl), 50.7 (d, MeCHPh), 71.9 (d, OCH), 125.8, 127.3, 128.5 (3 d,
Ph), 143.0 (s, Ph), 153.9 (s, C=O). IR (CHCl3) cm–1: 1725 (C=O). MS (EI) m/z: 279 (M+), 277 (M+), 275
(M+), 264, 262, 260, 164, 105. [α]D23 –42.8° (c 2.4, CHCl3). Anal. Calcd for C12H15NO3Cl2: C, 52.19; H,
5.47; N, 5.07. Found: C, 52.30; H, 5.47; N, 5.05.
1,3-Dibromo-2-propyl (S)-N-[1-(1-naphthyl)ethyl]carbamate (6c). White solid, mp 84–86 °C (ethyl
1
acetate). H-NMR (CDCl3) δ: 1.68 (3 H, d, J = 7.0, Me), 3.56–3.71 (4 H, m, 2 x CH2Br), 5.07 (1 H, m,
MeCHAr), 5.20 (1 H, br m, NH), 5.65 (1 H, m, OCH), 7.44–7.58 (4 H, m, Ar), 7.80 (1 H, d, J = 8.4, Ar),
7.88 (1 H, d, J = 7.3, Ar), 8.10 (1 H, d, J = 8.4, Ar). IR (CHCl3) cm–1: 1725 (C=O). MS (EI) m/z: 417
23
(M+), 415 (M+), 413 (M+), 214, 170, 155, 127. [α]D –4.1° (c 2.1, CHCl3). Anal. Calcd for
C16H17NO2Br2: C, 46.29; H, 4.13; N, 3.37. Found: C, 46.48; H, 4.16; N, 3.38.
Cyclization of the carbamates.
Typical procedure. Methylmagnesium bromide (3.0 mmol/mL solution in ether, 0.83 mL, 2.50 mmol)
was added dropwise to a stirred solution of 6a (700 mg, 1.92 mmol) in THF (30 mL) at –78 °C. The
mixture was stirred for 5 h at this temperature and saturated aqueous ammonium chloride solution was
added. After being warmed to rt, the mixture was extracted with methylene chloride. The organic extracts
were combined, dried with magnesium sulfate, and concentrated in vacuo. The residue was
chromatographed on silica gel (hexane:ethyl acetate = 4:1) to give 4a (336 mg, 62%) and 5a (130 mg,
24%). The other results are shown in Table 2.
(5R,1'S)-5-Bromomethyl-3-(1'-phenylethyl)-2-oxazolidinone (4a). White needles, mp 95–97 °C (ethyl
acetate). 1H-NMR (CDCl3) δ: 1.59 (3 H, d, J = 7.0, Me), 2.99 (1 H, dd, J = 8.9, 6.1 Hz, NCHH), 3.29 (1
H, dd, J = 10.6, 7.7, BrCHH), 3.44 (1 H, dd, J = 10.6, 4.0, BrCHH), 3.62 (1 H, t, J = 8.9, NCHH), 4.68
13
(1 H, m, OCH), 5.22 (1 H, q, J = 7.0, MeCHPh), 7.35 (5 H, m, Ph). C-NMR (CDCl3) δ: 16.2 (q, Me),
32.6 (t, NCH2), 44.1 (t, CH2Br), 51.4 (d, MeCHPh), 71.4 (d, OCH), 126.9, 127.9, 128.6 (3 d, Ph), 138.9
(s, Ph), 156.4 (s, C=O). IR (CHCl3) cm–1: 1780 (C=O). MS (EI) m/z: 285 (M+), 283 (M+), 270, 268, 204,
105. [α]D23 –33.1° (c 1.4, CHCl3). Anal Calcd for C12H14NO2Br: C, 50.72; H, 4.97; N, 4.93. Found: C,
51.00; H, 4.98; N, 4.85.
1
(5S,1'S)-5-Bromomethyl-3-(1'-phenylethyl)-2-oxazolidinone (5a). A colorless oil. H-NMR (CDCl3)
δ:1.62 (3 H, d, J = 7.0, Me), 3.28 (1 H, t, J = 8.9, NCHH), 3.36 (1 H, dd, J = 8.9, 5.7, NCHH), 3.47 (1 H,
dd, J = 10.6, 7.0, BrCHH), 3.54 (1 H, dd, J = 10.6, 3.7, BrCHH), 4.60 (1 H, m, OCH), 5.23 (1 H, q, J =
13
7.0, MeCHPh), 7.34 (5 H, m, Ph). C-NMR (CDCl3) δ: 16.1 (q, Me), 33.2 (t, NCH2), 44.1 (t, CH2Br),
51.4 (d, MeCHPh), 70.9 (d, OCH), 126.9, 127.9, 128.6 (3 d, Ph), 139.0 (s, Ph), 156.4 (s, C=O). IR (neat)
cm–1: 1750 (C=O). MS (EI) m/z: 285 (M+), 283 (M+), 270, 268, 204, 105. [α]D –32.2° (c 1.6, CHCl3).
23
Anal. Calcd for C12H14NO2Br: C, 50.72; H, 4.97; N, 4.93. Found: C, 51.01; H, 4.98; N, 4.85.
(5R,1'S)-5-Chloromethyl-3-(1'-phenylethyl)-2-oxazolidinone (4b). White prisms, mp 68–70 °C (ethyl