PAPER
-(2,4,6-Tribromophenyl)-3,4-dihydroisoquinolinium Tetra-
Efficient Iminium Salt Catalysts for Epoxidation
3409
2
IR (film): 3048, 2996, 1628, 1604, 1573, 1485, 1423, 1378, 1314,
–
1
phenylborate (6)
1268, 1179, 1033, 896, 845 cm .
Prepared according to the general procedure from 2,4,6-tribromo-
aniline (0.70 g, 2.12 mmol); yellow powder (0.94 g, 58%); mp 186–
1
H NMR (400 MHz, CD CN): d = 3.32 (t, J = 7.2 Hz, 2 H), 3.85 (s,
3
6
6
H), 4.40 (t, J = 7.2 Hz, 2 H), 6.70–6.75 (m, 1 H), 6.80 (m, 5 H),
.98 (t, J = 6.0 Hz, 8 H), 7.24–7.29 (m, 8 H), 7.48–7.61 (m, 3 H),
1
89 °C (dec.).
IR (film): 3052, 2985, 1628, 1601, 1570, 1478, 1422, 1382, 1262,
7.80–7.93 (m, 2 H), 9.00 (s, 1 H).
–
1
1
209, 1146, 1031, 896, 857 cm .
13
C NMR (100 MHz, CD CN): d = 24.7, 51.3, 55.6, 100.8, 102.2,
3
1
H NMR (400 MHz, CD CN): d = 3.52 (t, J = 7.0 Hz, 2 H), 4.30 (t,
121.5, 124.7, 125.2, 125.3, 128.3, 128.4, 134.7, 135.4, 137.1, 139.1,
3
J = 7.0 Hz, 2 H), 6.83 (t, J = 6.0 Hz, 4 H), 6.98 (t, J = 6.0 Hz, 8 H),
144.1, 163.2 (q, J = 49.6 Hz), 166.6.
7
.24–7.29 (m, 8 H), 7.59–7.64 (m, 2 H), 7.59–8.00 (m, 2 H), 8.14
+
+
HRMS (ES ): m/z calcd for C H NO : 268.1332; found:
1
7
18
2
(
m, 2 H), 8.97 (s, 1 H).
2
68.1330.
1
3
C NMR (100 MHz, CD CN): d = 25.0, 51.4, 120.3, 121.5, 125.22,
3
Anal. Calcd for C H BNO ·0.5H O: C, 82.6; H, 6.6; N, 2.4.
Found: C, 82.8; H, 6.6; N, 2.4.
4
1
38
2
2
1
1
25.26, 125.30, 125.33, 128.86, 129.92, 135.4, 135.5, 135.6, 136.2,
41.3, 169.0 (q, J = 49.6 Hz), 172.9.
+
+
HRMS (ES ): m/z calcd for C H Br N : 441.8436; found:
Catalytic Epoxidation of Alkenes Mediated by Iminium Salts
Using Oxone; General Procedure
1
5
11
3
4
41.8434.
Oxone (2 equiv with respect to alkene) was added with stirring to an
Anal. Calcd for C H BBr N: C, 61.3; H, 4.1; N, 1.8. Found: C,
3
9
31
3
ice-cooled solution of Na CO (4 equiv) in water (12 mL per 1.50 g
2
3
6
1.1; H, 4.1; N, 1.8.
of Na CO ), and the resulting foaming solution was stirred for 5–10
2
3
min, until most of the initial effervescence subsided. A solution of
the iminium salt (10 mol% with respect to alkene) in MeCN (6 mL
per 1.50 g of Na CO used) was added, followed by a solution of the
2
-(2,6-Dimethylphenyl)-3,4-dihydroisoquinolinium Tetraphe-
nylborate (7)
2
3
Prepared according to the general procedure from 2,6-dimethyl-
aniline (2.0 g, 16.5 mmol); yellow powder (5.86 g, 64%); mp 189–
1
alkene substrate in MeCN (6 mL per 1.50 g of Na CO used). The
2
3
suspension was stirred with ice-bath cooling until the substrate was
completely consumed according to TLC. The reaction mixture was
91 °C (dec.).
IR (film): 3448, 3052, 2997, 1626, 1603, 1570, 1480, 1425, 1379,
1
then diluted with ice-cooled Et O (20 mL per 100 mg substrate) and
2
–
1
315, 1265, 1181, 1034, 895, 847 cm .
the same volume of water was added immediately. The aqueous
1
phase was washed with Et O (4 ×) and the combined organic phases
H NMR (400 MHz, CD CN): d = 2.32 (s, 6 H), 3.45 (t, J = 7.5 Hz,
2
3
were washed with brine and dried (MgSO ). Filtration and removal
2
6
3
H), 4.23 (t, J = 7.5 Hz, 2 H), 6.83 (t, J = 9.0 Hz, 4 H), 6.98 (t, J =
.0 Hz, 8 H), 7.20–7.40 (m, 8 H), 7.41–7.45 (m, 1 H), 7.55–7.70 (m,
H), 7.89–8.00 (m, 3 H), 8.85 (s, 1 H).
4
of the solvents gave a yellow or light brown residue, which was pu-
rified by column chromatography, typically using EtOAc–light PE
(
1:99) to provide the pure epoxide.
1
3
C NMR (100 MHz, CD CN): d = 16.5, 24.8, 51.2, 121.5, 125.2,
3
1
1
25.3, 128.48, 128.50, 129.2, 130.7, 132.3, 134.8, 135.4, 137.2,
a-Methylstyrene Oxide11
Colorless oil.
39.6, 164.4 (q, J = 50.0 Hz), 170.16.
+
+
HRMS (ES ): m/z calcd for C H N : 236.1434; found: 236.1434.
1
7
18
IR (neat): 3034, 2958, 2929, 2872, 1604, 1496, 1447, 1381, 1343,
–
1
Anal. Calcd for C H BN·1.0H O: C, 85.9; H, 7.0; N, 2.4. Found:
1061, 1027, 860, 759, 699 cm .
41
38
2
C, 86.1; H, 7.0; N, 2.5.
1
H NMR (250 MHz, CDCl ): d = 0.86 (d, J = 6.6 Hz, 3 H), 2.79 (dd,
3
J = 0.8, 5.4 Hz, 1 H), 2.96 (d, J = 5.4 Hz, 1 H), 7.24–7.38 (m, 5 H).
1
2
-(2,6-Diisopropylphenyl)-3,4-dihydroisoquinolinium Tetra-
3
C NMR (62.5 MHz, CDCl ): d = 21.7, 56.7, 56.9, 125.2, 127.4,
phenylborate (8)
Prepared according to the general procedure from 2,6-diisopropyl
aniline (0.75 g, 4.24 mmol); yellow powder (1.09 g, 42%); mp 210–
3
1
28.3, 129.0.
trans-a-Methylstilbene Oxide12
Colorless oil.
2
13 °C (dec.).
IR (film): 3051, 2980, 1632, 1603, 1570, 1423, 1385, 1264, 1176,
–1
IR (neat): 3061, 1602, 1495, 1449, 1381, 1279, 1157, 1118, 1065,
1
1
031, 896, 848 cm .
–
1
027, 980 cm .
1
H NMR (400 MHz, CD CN): d = 1.23 (d, J = 6.0 Hz, 6 H), 1.28 (d,
3
1
H NMR (400 MHz, CDCl ): d = 1.46 (s, 3 H), 3.96 (s, 1 H), 7.30–
J = 6.0 Hz, 6 H), 2.86 (sept, J = 6.0 Hz, 2 H), 3.46 (t, J = 7.0 Hz, 2
H), 4.23 (t, J = 7.0 Hz, 2 H), 6.83 (t, J = 6.0 Hz, 4 H), 6.98 (t, J =
3
7
13
.46 (m, 10 H).
6
4
.0 Hz, 8 H), 7.23–7.34 (m, 8 H), 7.44–7.47 (m, 1 H), 7.55–7.89 (m,
H), 7.89–7.92 (m, 2 H), 8.93 (s, 1 H).
C NMR (100 MHz, CDCl ): d = 17.1, 63.5, 67.5, 125.6, 126.9,
3
1
27.7, 127.9, 128.6, 129.2, 136.4, 142.8.
1
3
C NMR (100 MHz, CD CN): d = 23.0, 23.4, 24.7, 28.4, 51.3, 53.3,
3
Triphenylethylene Oxide13
Colorless oil, which slowly solidified; mp 66–67 °C (Lit. mp 75
C).
1
1
21.5, 125.2, 125.3, 128.5, 128.6, 131.5, 135.0, 135.4, 135.5, 137.1,
39.8, 142.7, 163.4 (q, J = 49.8 Hz), 169.7.
1
3
°
+
+
HRMS (ES ): m/z calcd for C H N : 292.2060; found: 292.2057.
2
1
26
IR (neat): 3062, 3030, 2957, 2925, 2856, 1605, 1596, 1499, 1471,
1
Anal. Calcd for C H BN·0.33H O: C, 87.5; H, 7.6; N, 2.3. Found:
–1
45
46
2
448, 1262, 1221, 741, 698, 621 cm .
C, 87.5; H, 7.6; N, 2.3.
1
H NMR (250 MHz, CDCl ): d = 4.40 (m, 1 H), 7.10–7.47 (m, 15
3
H).
13
2
-(3,5-Dimethoxyphenyl)-3,4-dihydroisoquinolinium Tetraphe-
nylborate (9)
C NMR (62.5 MHz, CDCl ): d = 68.0, 68.3, 126.3, 126.8, 127.5,
3
Prepared according to the general procedure from 3,5-dimethoxy-
aniline (0.30 g, 1.96 mmol); yellow powder (0.92 g, 80%); mp 169–
1
27.6, 127.7, 127.8 128.0, 128.2, 128.6, 135.4, 135.9, 141.1.
1
73 °C (dec.).
Synthesis 2005, No. 19, 3405–3411 © Thieme Stuttgart · New York