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N. B. KONDEKAR AND P. KUMAR
allowed to warm to room temperature and stirred for 5 h. After diluting with 25 mL
CH2Cl2, the solution was washed with water (3 ꢀ 15 mL), and brine, dried over
Na2SO4, and concentrated to give the crude mesylated product. Silica-gel column
chromatographic purification of the crude product gave mesylate 8 as a colorless
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liquid (1.33 g, 85%). ½aꢄD : ꢃ32.81 (c 1.44, CHCl3); IR (CHCl3, cmꢃ1): nmax 3029,
2360, 2341, 1604, 1496, 1350, 1174. 1H NMR (200 MHz, CDCl3): d 1.49 (d, J ¼ 6.3 Hz,
3H), 2.50 (s, 3H), 2.93–2.98 (m, 2H), 4.81–4.97 (m, 1H), 7.23–7.38 (m, 5H) ppm. 13
C
NMR (100 MHz, CDCl3): d 20.9, 37.2, 42.5, 80.8, 126.6, 128.2, 129.2, 136.5 ppm.
Analysis calcd.: C, 56.05; H, 6.59; S, 14.96. Found: C, 56.19; H, 6.73; S, 14.83.
Synthesis of (R)-(2-Azidopropyl)benzene (9)
NaN3 (1.82 g, 28.00 mmol) was added portionwise to a solution of mesylated
product 8 (1 g, 4.66 mmol) in dry DMF (10 mL), and the resulting suspension was
stirred for 8 h at 50 ꢁC. After cooling the reaction mixture to room temperature,
Et2O (15 mL) and H2O (15 mL) were added and the aqueous layer was extracted with
Et2O (3 ꢀ 10 mL). The combined organic layers were dried over Na2SO4, and the
solvent was removed under reduced pressure. Silica-gel column chromatographic
purification of the crude product gave azide 9 as a yellowish liquid (0.458 g, 61%).
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½aꢄD : ꢃ66.49 (c 0.92, CHCl3), Lit.[5b] ½aꢄD : ꢃ49.5 (c 1.24, CHCl3); IR (CHCl3,
cmꢃ1): nmax 3029, 2110, 1604, 1496, 1453, 1255, 1085. H NMR (200 MHz, CDCl3):
1
d 1.24 (d, J ¼ 6.7 Hz, 3H), 2.65–2.88 (m, 2H), 3.62–3.72 (m, 1H), 7.17–7.34 (m, 5H)
ppm. 13C NMR (75 MHz, CDCl3): d 18.7, 42.3, 58.3, 126.4, 128.2, 129.1, 137.6 ppm.
Analysis calcd.: C, 67.06; H, 6.88; N, 26.07. Found: C, 67.25; H, 7.03; N, 26.21.
Synthesis of tert-Butyl (R)-1-Phenyl Propan-2-yl Carbamate (10)
To a solution of azide 9 (1.0 g, 6.2 mmol) in ethyl acetate were added 10%
Pd=C (50 mg) and Boc2O (1.63 mL, 6.82 mmol). The resulting solution was stirred
under hydrogen atmosphere for 12 h at room temperature until disappearance of
the azido alcohol as monitored by thin-layer chromatography (TLC). The reac-
tion mixture was filtered through a celite pad to remove the catalyst, and the
filtrate was concentrated in vacuo. Silica-gel column chromatography of the
crude product using EtOAc=petroleum ether (1:19) as eluent gave 10 (1.31 g,
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90%) as a colorless liquid. ½aꢄD : þ7.5 (c 0.8, CHCl3), Lit.[5b] ½aꢄD : þ7.62 (c 0.8,
CHCl3); IR (CHCl3, cmꢃ1): 3360, 2978, 1703, 1508, 1456, 1250, 1173, 1061; H
1
NMR (200 MHz, CDCl3): d 1.07 (d, J ¼ 6.7 Hz, 3H), 1.44 (s, 9H), 2.67 (dd,
J ¼ 13.3, 7.5 Hz, 1H), 2.83 (dd, J ¼ 13.3, 7.5 Hz, 1H), 3.84–3.98 (m, 1H), 4.41
(brs, 1H), 7.20–7.31 (m, 5H); 13C NMR (75 MHz, CDCl3): d 19.7, 28.0, 42.7,
47.3, 78.3, 125.8, 127.8, 129.0, 138.1, 154.8. Analysis: C14H21NO2 calcd. C,
71.46; H, 8.99; N, 5.95. Found: C, 71.57; H, 8.89; N, 5.85.
Synthesis of (R)-N-Methyl-1-phenylpropan-2-amine (11)
Methylamine (40% in water, 8.2 mL, 105.3 mmol) was added to a solution of
mesylate 8 (0.48 g, 2.63 mmol) in DMF (15 mL) at room temperature. After the
mixture was stirred at 50 ꢁC for 12 h, another portion of methylamine (4.1 mL,