C. Paizs et al. / Tetrahedron: Asymmetry 14 (2003) 1495–1501
1499
3
.3.2. 1-(5-Bromobenzofuran-2-yl)ethanol rac-5b. Yield:
3.87 (2H, m), 4.89 (1H, m), 6.97 (1H, s), 7.64 (1H, d),
1
13
8
3%. Mp: 50°C; H NMR: 1.63 (3H, d), 2.26 (1H,
8.20 (1H, d), 8.51 (1H, s); C NMR (DMSO-d ): 65.37,
6
broad s), 5.00 (1H, q), 6.55 (1H, s), 7.27–7.37 (2H, m),
69.98, 105.53, 112.67, 118.51, 120.96, 130.38, 145.63,
159.17, 163.41; IR: 3232, 2992, 1960, 1624, 1616, 1592,
1572, 1480, 1396, 1284, 1192, 1176, 1132, 1080, 1040,
1000, 984, 964, 948, 912, 856, 796, 764, 700. Anal. calcd
for C H NO : C, 53.82; H, 4.06; N, 6.28. Found: C,
1
3
7
1
2
8
3
.66 (1H, s); C NMR: 21.47, 64.14, 101.36, 112.69,
15.84, 123.75, 127.11, 130.20, 153.58, 161.69; IR: 3408,
984, 1448, 1372, 1300, 1264, 1152, 1088, 1024, 936,
08. Anal. calcd for C H BrO : C, 49.82; H, 3.76; Br,
10
9
2
10
9
5
3.14. Found: C, 49.76; H, 3.65; Br, 33.05%.
53.82; H, 4.12; N, 6.33%.
3
8
2
.3.3. 1-(5-Nitrobenzofuran-2-yl)ethanol rac-5c. Yield:
3
.5. Preparation of racemic 1-acetoxy-1-(benzofuran-2-
25
1
3%. Mp: 75°C (lit. 73–76°C); H NMR: 1.66 (3H, d),
yl)ethanes rac-7a–d
.42 (1H, broad s), 5.06 (1H, q), 6.75 (1H, s), 7.51 (1H,
1
3
d), 8.18 (1H, d), 8.43 (1H, s); C NMR: 21.50, 64.06,
To a solution of alcohol rac-5a–d, (0.3 mmol) and
triethylamine (33.5 mg, 46 ml, 0.33 mmol) in CH Cl (2
ml) acetylchloride (26 mg, 24 ml, 0.33 mmol) was added
and the mixture was stirred at rt for 2 h. The reaction
mixture was poured in water (10 ml) and extracted with
CH Cl (20 ml, twice). The organic layer was dried over
1
1
1
5
6
02.58, 111.54, 117.57, 120.94, 128.64, 144.16, 157.64,
63.91; IR: 3320, 1528, 1348, 1296, 1264, 1160, 1080,
024, 884, 816, 736. Anal. calcd for C H NO : C,
2
2
1
0
9
4
7.97; H, 4.38; N, 6.76. Found: C, 57.92; H, 4.27; N,
.77%.
2
2
MgSO , concentrated and the residue was purified by
4
3
.3.4.
1-(7-Methoxybenzofuran-2-yl)ethanol
rac-5c.
vacuum-chromatography (eluent: CH Cl –acetone 9:1,
2
2
1
Semisolid. Yield: 83%; H NMR: 1.64 (3H, d), 2.46
v:v) yielding the racemic acetates (rac-7a–d) as colorless
semisolids.
(
6
5
1
1
9
1H, broad s), 4.00 (3H, s), 5.03 (1H, q), 6.60 (1H, s),
1
3
.76–6.80 (1H, m), 7.14 (2H, d); C NMR: 21.41,
5.98, 64.08, 102.02, 106.29, 113.46, 123.46, 129.86,
43.96, 145.26, 160.64; IR: 3296, 2984, 1624, 1600,
496, 1440, 1376, 1312, 1272, 1200, 1184, 1096, 1032,
36, 892, 836, 728. Anal. calcd for C H O : C, 68.74;
3
.5.1.
Yield: 90%; H NMR: 1.71 (3H, d), 2.13 (3H, s), 6.13
1H, q), 6.72 (1H, s), 7.24–7.29 (1H, m), 7.31–7.34 (1H,
1-Acetoxy-1-(benzofuran-2-yl)ethane
rac-7a.
1
(
1
1
12
3
13
m), 7.51 (1H, d), 7.58 (1H, d); C NMR: 18.43, 21.16,
H, 6.29. Found: C, 68.66; H, 6.25%.
6
1
1
5.51, 104.24, 111.37, 121.24, 122.87, 124.56, 127.86,
54.86, 155.99, 170.12; IR: 1744, 1456, 1372, 1236,
060, 1028, 752; GC (165°C) RT(R): 3.75 min, RT(S): 3.84
3
1
.4. Preparation of racemic 1-(benzofuran-2-yl)ethane-
,2-diols rac-6a-c
min; HPLC ((S,S)-Whelk-O1, 1 ml/min) RT(S): 3.88
min, RT(R): 5.25 min, ((R,R)-Whelk-O1, 1 ml/min)
RT(R): 4.4 min, RT(S): 6.37 min. Anal. calcd for
C H O : C, 70.57; H, 5.92. Found: C, 70.62; H,
Chemical reduction of hydroxymethyl ketones 3a–c
100 mg) by NaBH in methanol was performed as
(
4
12
12
3
described in Section 3.3.
5
.95%.
3
7
3
.4.1. 1-(Benzofuran-2-yl)ethane-1,2-diol rac-6a. Yield:
2
8
1
3
7
6
.5.2. 1-Acetoxy-1-(5-bromobenzofuran-2-yl)ethane rac-
5%. Mp: 85°C (lit. 87–88); H NMR (MeOH-d ):
4
1
b. Yield: 85%; H NMR: 1.66 (3H, d), 2.11 (3H, s),
.82–3.93 (2H, m), 4.81–4.83 (1H, m), 6.73 (1H, s), 7.18
.07 (1H, q), 6.63 (1H, s), 7.33–7.39 (2H, m), 7.67 (1H,
(
1H, t), 7.16–7.26 (1H, m), 7.43 (1H, d), 7.53 (1H, d);
13
1
3
s); C NMR: 18.80, 21.52, 65.68, 104.05, 113.24,
16.30, 124.27, 127.87, 130.26, 153.99, 157.84, 170.44;
IR: 1740, 1448, 1372, 1264, 1024, 800; GC (120–170°C,
C NMR (MeOH-d ): 65.87, 70.19, 104.59, 112.05,
4
1
1
2
1
7
1
22.12, 123.88, 125.21, 129.78, 156.40, 159.30; IR: 3272,
984, 1960, 1712, 1672, 1576, 1484, 1392, 1280, 1192,
152, 1136, 1128, 1084, 996, 984, 956, 920, 912, 808,
64, 736; HPLC ((S,S)-Whelk-O1, 1.5 ml/min) RT(S)
5.28 min, RT(R): 20.37 min. Anal. calcd for C H O :
1
°C/min) RT(R): 37.34 min, RT(S): 38.06 min; HPLC
(S,S)-Whelk-O1, 1 ml/min) RT(S): 4.07 min, RT(R): 5.45
min, ((R,R)-Whelk-O1, 1 ml/min) RT(R): 4.42 min,
RT(S): 6.04 min. Anal. calcd for C H BrO : C, 50.91;
(
:
10
10
3
C, 67.41; H, 5.66. Found: C, 67.45; H, 5.58%.
12 11
3
H, 3.92; Br, 28.22. Found: C, 50.82; H, 3.88; Br,
2
8.34%.
3
.4.2. 1-(5-Bromobenzofuran-2-yl)ethane-1,2-diol rac-6b.
1
Yield: 79%. Mp: 135°C; H NMR (DMSO-d ): 3.87–
6
3
.97 (2H, m), 4.82–4.84 (1H, m), 6.97 (1H, s), 7.64 (1H,
3
.5.3. 1-Acetoxy-1-(5-nitrobenzofuran-2-yl)ethane rac-
13
1
d), 8.20 (1H, d), 8.51 (1H, s); C NMR (DMSO-d6):
7c. Yield: 93%; H NMR: 1.70 (3H, d), 2.13 (3H, s),
6
1
1
1
5.37, 69.98, 105.53, 112.67, 118.51, 120.96, 130.38,
45.63, 159.17, 163.41; IR: 3268, 2988, 1962, 1718,
662, 1556, 1464, 1388, 1282, 1190, 1154, 1132, 1124,
080, 992, 948, 924, 916, 818, 756; HPLC ((S,S)-Whelk-
6
8
1
1
.10 (1H, q), 6.83 (1H, s), 7.55 (1H, d), 8.23 (1H, d),
13
.48, (1H, s); C NMR: 18.42, 21.08, 65.10, 104.85,
11.78, 117.8, 120.48, 128.34, 144.31, 157.61, 159.66,
69.70; IR: 1748, 1524, 1348, 1232, 1064, 1032, 952; GC
O1, 1.5 ml/min) RT(S): 33.77 min, RT(R): 36.37 min.
Anal. calcd for C H BrO : C, 46.72; H, 3.53; Br, 31.08.
Found: C, 46.65; H, 3.58; Br, 31.15%.
(130–180°C, 1°C/min) RT(R)
: 46.94 min, RT(S): 47.56
10
9
3
min; HPLC ((S,S)-Whelk-O1, 2 ml/min) RT(S): 4.09
min, RT(R): 5.12 min, ((R,R)-Whelk-O1, 1 ml/min)
RT(R): 4.75 min, RT(S): 6.03 min. Anal. calcd for
C H NO : C, 57.83; H, 4.45; N, 5.62. Found: C,
3
.4.3. 1-(5-Nitrobenzofuran-2-yl)ethane-1,2-diol rac-6c.
12
11
5
1
Yield: 74%. Mp: 113°C; H NMR (DMSO-d ): 3.97–
57.75; H, 4.52; N, 5.68%.
6