Chemistry - A European Journal
10.1002/chem.201705929
FULL PAPER
Radical trapping: Compounds 1a-5a (1 eq) in CH
3
CN (2 mL) and 1b-
59.90, 55.93, 53.22, 39.59, 32.96, 32.68, 20.32, 19.89, 16.97. HRMS-
+
+, 425.3163; found: 425.3138.
5b (1 eq) in MeOH (2 mL) were added TEMPO (10 eq) at rt while stirring.
ESI (+) (m/z): [M-Br] calcd. for C27
H N O
41 2 2
The resulting mixture was allowed to react upon UV irradiation until all
starting material was consumed. Solvent was removed and the residue
was purified by chromatography (Hexane: DCM = 10:1 for 1a-5a, DCM:
Methanol = 10:1 for 1b-5b) to afford the trapping adducts 1e-5e, 1f-4f,
and 4g.
1
-(3-Methoxy-5-(((2,2,6,6-tetramethylpiperidin-1-
yl)oxy)methyl)phenyl)-N,N,N-trimethylmethanaminium (3f): H NMR
300 MHz, CDCl -d): δ. 7.23 (s, 1H), 7.06 (s, 1H), 6.99 (s, 1H), 4.94 (s,
H), 4.80 (s, 2H), 3.84 (s, 3H), 3.45 (s, 9H), 1.53-1.32 (m, 6H), 1.19 (s,
H), 1.13(s, 6H). 13C NMR (75 MHz, CDCl
-d): δ. 160.12, 141.25,
1
(
2
6
3
3
1
-((3-(Bromomethyl)-2,5-dimethoxybenzyl)oxy)-2,2,6,6-
tetramethylpiperidine (1e): 1H NMR (300 MHz, CDCl
-d): δ. 7.10 (s,
H), 6.86 (s, 1H), 4.89 (s, 2H), 4.58 (s, 2H), 3.86-3.83 (d, J = 9.0 Hz, 6H),
.58-1.51 (m, 6H), 1.28-1.18 (d, J = 30 Hz, 12H). 13C NMR (75 MHz,
-d): δ. 155.82, 149.46, 133.31, 131.55, 115.77, 114.24, 73.25,
2.21, 60.05, 55.55, 39.76, 33.01, 28.12, 20.41, 17.10. HRMS-ESI (+)
128.44, 123.17, 117.19, 115.32, 69.21, 60.01, 55.73, 52.88, 39.63,
+
+,
3
33.09, 20.31, 17.03. HRMS-ESI (+) (m/z): [M-Br] calcd. for C21
H N O
37 2 2
1
1
349.2850; found: 349.2822.
CDCl
6
3
1
-(2-Bromo-5-methoxy-3-(((2,2,6,6-tetramethylpiperidin-1-
1
yl)oxy)methyl)phenyl)-N,N,N-trimethylmethanaminium (4f): H NMR
+
+
(
3
m/z): [M+H] calcd. for C19H31NO Br , 400.1482; found: 400.1475.
(
(
300 MHz, Methanol-d
s, 2H), 3.92 (s, 3H), 3.26 (s, 9H), 1.57-1.56 (m, 6H), 1.23 (d, 12H). 13C
): δ. 159.07, 141.17, 128.70, 118.69, 116.78,
4
): δ. 7.38 (s, 1H), 7.27 (s, 1H), 4.94 (s, 2H), 4.81
1
2
7
2
-((6-(Bromomethyl)-4-methoxy-[1,1'-biphenyl]-2-yl)methoxy)-
NMR (75 MHz, Methanol-d
4
,2,6,6-tetramethylpiperidine (2e): 1H NMR (300 MHz, CDCl
116.09, 78.01, 67.81, 59.94, 54.98, 52.62, 39.36, 31.97, 19.44, 16.63.
3
-d): δ.
+
+
.42-7.40 (m, 3H), 7.27-7.21 (m, 3H), 7.00 (s, 1H), 4.48 (s, 2H), 4.23 (s,
H), 3.91 (s, 3H), 1.62-1.23 (m, 6H), 1.11-1.00 (d, J = 33 Hz, 12H). 13C
HRMS-ESI (+) (m/z): [M-Br] calcd. for C21
H
36
N
2
O
2
Br , 427.1955; found:
427.1931.
3
NMR (75 MHz, CDCl -d): δ. 158.88, 138.84, 137.46, 136.92, 133.29,
1
3
C
29.85, 128.28, 127.43, 114.54, 113.51, 59.86, 55.32, 39.67, 39.60,
1
,1'-(((2-Bromo-5-methoxy-1,3-
phenylene)bis(methylene))bis(oxy))bis(2,2,6,6-
tetramethylpiperidine) (4g): 1H NMR (300 MHz, CDCl
2.66, 32.37, 20.32, 17.05. HRMS-ESI (+) (m/z): [M+H]+ calcd. for
+
24
H
33NO
2
Br , 446.1689; found: 446.1678.
3
-d): δ. 7.13 (s,
2
H), 4.89 (s, 4H), 3.88 (s, 3H), 1.59-1.53 (m, 12H), 1.22-1.13 (m, 24H).
1
3C NMR (75 MHz, CDCl
1
-((3-(Bromomethyl)-5-methoxybenzyl)oxy)-2,2,6,6-
tetramethylpiperidine (3e): 1H NMR (300 MHz, CDCl
H), 6.91-6.87 (m, 2H), 4.83 (s, 2H), 4.50 (s, 2H), 3.86 (s, 3H), 1.53-1.51
m, 6H), 1.27-1.20 (m, 12H). 13C NMR (75 MHz, CDCl
-d): δ. 159.82,
3
-d): δ. 158.69, 139.13, 112.29, 111.14, 60.06,
+
3
-d): δ. 6.97 (s,
55.33, 39.73, 32.93, 20.44, 17.11. HRMS-ESI (+) (m/z): [M+H] calcd.
for C27
+
1
(
H
46
N
2
O
3
Br , 525.2686; found: 525.2679.
3
1
3
C
40.53, 138.92, 120.12, 113.32, 113.07, 60.05, 55.32, 39.74, 33.63,
2
Carbocation trapping: MeONH ·HCl (40 eq) in DMF (2 mL) was added
3.10, 20.36, 17.13. HRMS-ESI (+) (m/z): [M+H]+ calcd. for
trimethylamine (44 eq.). After stirring at rt for 30 min, 2a-4a (1 eq.) in
DMF or 2b-4b (1 eq.) in MeOH were added. The resulting mixture was
stirred for 20 min, then irradiated with 350 nm light until the starting
material was consumed. The reaction was quenched by water and
extracted with ethyl acetate (3 × 3 mL). The combined organic phases
were washed with brine and dried over anhydrous Na SO . After
2 4
removing solvent, the residue was purified by chromatography (Hexane:
ethyl acetate = 5:1) to provide the corresponding trapping adducts 2d-
5d.
+
18
H
29NO
2
Br , 370.1376; found: 370.1370.
1
-((2-Bromo-3-(bromomethyl)-5-methoxybenzyl)oxy)-2,2,6,6-
tetramethylpiperidine (4e): 1H NMR (300 MHz, CDCl
-d): δ. 7.19 (s,
H), 6.94 (s, 1H), 4.89 (s, 2H), 4.63 (s, 2H), 3.86 (s, 3H), 1.6-1.53 (m,
H), 1.23-1.22 (d, J = 3.3 Hz, 12H). 13C NMR (75 MHz, CDCl
-d): δ.
3
1
6
1
3
3
58.81, 140.64, 137.65, 114.55, 113.80, 60.10, 55.47, 39.72, 33.99,
2.91, 20.46, 17.10. HRMS-ESI (+) (m/z): [M+H]+ calcd. for
18 2 2
C H28NO Br
+, 448.0481; found: 448.0475.
N,N'-((4-Methoxy-[1,1'-biphenyl]-2,6-diyl)bis(methylene))bis(O-
1
1
-((3-(Bromomethyl)-5-methoxy-2-nitrobenzyl)oxy)-2,2,6,6-
methylhydroxylamine) (2d): H NMR (300 MHz, CDCl
3
-d): δ. 7.43-7.40
+
tetramethylpiperidine (5e): HRMS-ESI (+) (m/z): [M+H] calcd. for
C H N O Br
18 28 2 4 2
+, 415.1227; found: 415.1220 (Note: the amount of 5e
(m, 3H), 7.25-7.23 (d, J = 6.0 Hz, 2H), 7.00 (s, 2H), 5.49 (s, 2H), 3.89 (s,
3H), 3.78 (s, 4H), 3.43-3.42 (d, J = 3.0 Hz, 6H). 13C NMR (75 MHz,
obtained was not sufficient to conduct NMR analysis due to an extremely
slow reaction).
CDCl
3
-d): δ. 158.75, 138.37, 136.99, 134.46, 129.96, 128.41, 127.36,
+
114.00, 61.42, 55.31, 53.70. HRMS-ESI (+) (m/z): [M+H] calcd. for
C H N O
17 23 2 3
+, 303.1703; found: 303.1683.
1
-(2,5-Dimethoxy-3-(((2,2,6,6-tetramethylpiperidin-1-
1
yl)oxy)methyl)phenyl)-N,N,N-trimethylmethanaminium (1f): H NMR
N,N'-((5-Methoxy-1,3-phenylene)bis(methylene))bis(O-
methylhydroxylamine) (3d): 1H NMR (300 MHz, CDCl
-d): δ. 6.94 (s,
1H), 6.85 (s, 1H), 5.74 (s, 1H), 4.04 (s, 4H), 3.83 (s, 3H), 3.54 (s, 6H).
(
300 MHz, Methanol-d
4
): δ. 7.28 (s, 1H), 7.09 (s, 1H), 4.94 (s, 2H), 4.55
3
(s, 2H), 3.86 (s, 3H), 3.79 (s, 3H), 3.14 (s, 9H), 1.55-1.53 (m, 6H), 1.27-
1
1
5
.19 (d, J = 24 Hz, 12H). 13C NMR (75 MHz, Methanol-d
51.38, 133.78, 121.61, 117.97, 117.64, 73.10, 64.06, 62.01, 59.87,
4.91, 52.18, 39.39, 32.07, 19.39, 16.64. HRMS-ESI (+) (m/z): [M-Br]+
4
): δ. 156.04,
13C NMR (75 MHz, CDCl
3
-d): δ. 159.84, 139.26, 121.44, 113.38, 61.85,
56.09, 55.27. HRMS-ESI (+) (m/z): [M+H]+ calcd. for C11 +,
H N O
19 2 3
227.1390; found: 227.1380.
39 2 3
calcd. for C22H N O
+, 379.2955; found: 379.2945.
N,N'-((2-Bromo-5-methoxy-1,3-phenylene)bis(methylene))bis(O-
methylhydroxylamine) (4d): 1H NMR (300 MHz, CDCl
-d): δ. 6.94 (s,
2H), 5.94 (s, 2H), 4.17 (s, 4H), 3.83 (s, 3H), 3.57 (s, 6H). 13C NMR (75
MHz, CDCl -d): δ. 158.55, 138.28, 116.10, 115.87, 61.64, 56.31, 55.47.
HRMS-ESI (+) (m/z): [M+H] calcd. for C11H N O Br , 304.0417; found:
18 2 3
304.0408.
1
[
(
2
6
1
-(4-Methoxy-6-(((2,2,6,6-tetramethylpiperidin-1-yl)oxy)methyl)-
1,1'-biphenyl]-2-yl)-N,N,N-trimethylmethanaminium (2f): 1H NMR
300 MHz, CDCl -d): δ. 7.48-7.35 (m, 5H), 7.12-7.09 (d, 2H), 4.76 (s,
H), 4.47 (s, 2H), 3.92 (s, 3H), 3.17 (s, 9H), 1.41-1.40 (m, 6H), 1.08 (s,
H), 0.97(s, 6H). 13C NMR (75 MHz, CDCl
-d): δ. 158.89, 139.80,
36.85, 135.27, 130.67, 129.00, 128.22, 126.38, 117.80, 117.07, 66.29,
3
3
3
+
+
3
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