Visible-Light-Induced Meerwein Cascade Reactions
in the electrospray ionization (ESI) mode. Elemental analyses were
performed on a Yanagimoto MT3CHN recorder.
δ = 7.46 (d, J = 5 Hz, 2 H), 7.04 (d, J = 5 Hz, 2 H), 4.09 (s, 2 H),
3.86 (s, 3 H), 3.72 (s, 3 H) ppm. 13C NMR (126 MHz, CDCl3): δ
= 171.2, 162.9, 141.3, 131.2, 130.6, 128.5, 52.1, 34.8 ppm. MS
(ESI): m/z = 215 [M + 1]+. C9H10O4S (214.24): calcd. C 50.46, H
4.70; found C 50.11, H 4.54.
Preparation of α-Aryl Ester 3: A 10 mL reaction vessel with a mag-
netic stirring bar was charged with Ru(bpy)3Cl2·6H2O (7.5 mg,
2 mol-%), aryl diazonium tetrafluoroborate 1 (0.5 mmol), acryloni-
trile (5 equiv., 2.5 mmol), and methanol (2 mL). The mixture was
irradiated with a blue LED (5 W) and stirred at room temp. under
oxygen overnight. Upon completion of the reaction, the solvent
was removed under reduced pressure. Purification of the crude
product was achieved by flash column chromatography (petroleum
ether/ethyl acetate, 5:1–10:1).
Methyl 2-(4-Chloro-2-nitrophenyl)acetate (3i): Light yellow solid
1
(85 mg, 74% yield); m.p. 46–48 °C. H NMR (500 MHz, CDCl3):
δ = 8.10 (d, J = 8.5 Hz, 1 H), 7.47–7.44 (m, 1 H), 7.36 (d, J =
2.5 Hz, 1 H), 4.01 (s, 2 H), 3.73 (s, 3 H) ppm. 13C NMR (126 MHz,
CDCl3): δ = 169.9, 147.1, 140.0, 133.4, 131.8, 128.9, 126.9, 52.5,
39.6 ppm. MS (ESI): m/z = 230 [M + 1]+. C9H8ClNO4 (229.62):
calcd. C 47.08, H 3.51, N 6.10; found C 47.37, H 3.75, N 5.88.
Methyl 2-(4-Nitrophenyl)acetate (3a): Light yellow oil (80 mg, 82%
yield). 1H NMR (500 MHz, CDCl3): δ = 8.19 (d, J = 8.6 Hz, 2 H),
7.46 (d, J = 8.6 Hz, 2 H), 3.74 (s, 2 H), 3.72 (s, 3 H) ppm. 13C
NMR (126 MHz, CDCl3): δ = 169.6, 146.3, 140.2, 129.3, 122.8,
51.4, 39.8 ppm. MS (ESI): m/z = 196 [M + 1]+. C6H9NO4 (159.14):
calcd. C 55.39, H 4.65, N 7.18; found C 55.12, H 4.79, N 7.27.
Methyl 2-(4-Nitrophenyl)propanoate (3l): Yellow oil (28 mg, 27%
yield). 1H NMR (400 MHz, CDCl3): δ = 8.21 (d, J = 8.8 Hz, 2 H),
7.50 (d, J = 8.7 Hz, 2 H), 3.87 (m, 1 H), 3.71 (s, 3 H), 1.57 (d, J =
7.2 Hz, 3 H) ppm. 13C NMR (101 MHz, CDCl3): δ = 173.7, 147.7,
147.2, 128.5, 123.9, 52.4, 45.3, 18.4 ppm. MS (ESI): m/z = 210 [M
+ 1]+. C10H11NO4 (209.20): calcd. C 57.41, H 5.30, N 6.70; found
C 57.22, H 5.17, N 6.89.
Methyl 2-(2-Nitrophenyl)acetate (3b): Light yellow oil (74 mg, 76%
yield). 1H NMR (500 MHz, CDCl3): δ = 8.25–8.08 (m, 2 H), 7.66–
7.58 (m, 1 H), 7.52 (t, J = 7.8 Hz, 1 H), 3.75 (s, 2 H), 3.73 (s, 3
H) ppm. 13C NMR (126 MHz, CDCl3): δ = 170.9, 135.8, 129.6,
124.5, 122.4, 52.5, 40.6 ppm. MS (ESI): m/z = 196 [M + 1]+.
C6H9NO4 (159.14): calcd. C 55.39, H 4.65, N 7.18.; found C 55.06,
H 4.85, N 7.07.
Ethyl 2-(4-Nitrophenyl)acetate (3n): Light yellow solid (77 mg, 73%
1
yield); m.p. 60–62 °C. H NMR (400 MHz, CDCl3): δ = 8.30 (d, J
= 8.7 Hz, 2 H), 7.57 (d, J = 8.7 Hz, 2 H), 4.28 (q, J = 7.1 Hz, 2
H), 3.83 (s, 2 H), 1.37 (t, J = 7.1 Hz, 3 H) ppm. 13C NMR
(101 MHz, CDCl3): δ = 170.2, 141.5, 130.3, 123.8, 61.4, 41.1,
14.1 ppm. MS (ESI): m/z = 210 [M + 1]+. C10H11NO4 (209.20):
calcd. C 57.41, H 5.30, N 6.70; found C 57.17, H 5.42, N 6.55.
Methyl 2-(3-Nitrophenyl)acetate (3c): Light yellow oil (82 mg, 84%
yield). 1H NMR (500 MHz, CDCl3): δ = 8.13 (d, J = 8.2 Hz, 1 H),
7.60 (d, J = 7.4 Hz, 1 H), 7.49 (t, J = 7.8 Hz, 1 H), 7.36 (d, J =
7.6 Hz, 1 H), 4.04 (s, 2 H), 3.72 (s, 3 H) ppm. 13C NMR (126 MHz,
CDCl3): δ = 170.5, 148.9, 133.6, 133.0, 129.8, 128.8, 125.4, 52.4,
39.7 ppm. MS (ESI): m/z = 196 [M + 1]+. C6H9NO4 (159.14): calcd.
C 55.39, H 4.65, N 7.18; found C 55.22, H 4.79, N 7.09.
Propyl 2-(4-Nitrophenyl)acetate (3o): Light yellow solid (74 mg,
1
66% yield); m.p. 34–36 °C. H NMR (500 MHz, CDCl3): δ = 8.20
(d, J = 8.7 Hz, 2 H), 7.47 (d, J = 8.7 Hz, 2 H), 4.08 (t, J = 6.7 Hz,
2 H), 3.74 (s, 2 H), 1.65 (dd, J = 14.2, 6.9 Hz, 2 H), 0.92 (t, J =
7.4 Hz, 3 H ppm. 13C NMR (126 MHz, CDCl3): δ = 147.3, 141.6,
130.4, 123.8, 67.1, 41.2, 22.0, 10.4 ppm. MS (ESI): m/z = 224 [M
+ 1]+. C10H11NO4 (209.20): calcd. C 59.19, H 5.87, N 6.27; found
C 58.86, H 5.66, N 6.51.
Methyl 2-([1,1Ј-Biphenyl]-4-yl)acetate (3d): Light yellow oil
1
(100 mg, 88% yield). H NMR (500 MHz, CDCl3): δ = 7.51 (m, 4
H), 7.37 (t, J = 7.6 Hz, 2 H), 7.32–7.27 (m, 3 H), 3.66 (s, 3 H), 3.62
(s, 2 H) ppm. 13C NMR (126 MHz, CDCl3): δ = 172.1, 140.9,
140.2, 133.1, 129.8, 128.9, 127.5, 127.3, 52.2, 40.9 ppm. MS (ESI):
m/z = 227 [M + 1]+. C15H14O2 (226.27): calcd. C 79.62, H 6.24;
found C 79.44, H 6.56.
Butyl 2-(4-Nitrophenyl)acetate (3p): Light yellow oil (71 mg, 60%
1
yield). H NMR (500 MHz, CDCl3): δ = 8.21–8.00 (m, 2 H), 7.43
(d, J = 8.5 Hz, 2 H), 4.07 (t, J = 6.7 Hz, 2 H), 3.70 (s, 2 H), 1.57
(dt, J = 14.6, 6.8 Hz, 2 H), 1.41–1.21 (m, 2 H), 0.86 (t, J = 7.4 Hz,
3 H) ppm. 13C NMR (126 MHz, CDCl3): δ = 170.3, 147.2, 141.7,
130.4, 123.7, 65.3, 41.1, 30.6, 19.1, 13.7 ppm. MS (ESI): m/z = 238
[M + 1]+. C12H15NO4 (237.25): calcd. C 60.75, H 6.37, N 5.90;
found C 60.58, H 6.51, N 5.72.
Methyl 2-(4-Cyanophenyl)acetate (3e): Light yellow oil (75 mg, 85%
yield). 1H NMR (400 MHz, CDCl3): δ = 7.65 (d, J = 8.2 Hz, 2 H),
7.42 (d, J = 8.2 Hz, 2 H), 3.74 (s, 3 H), 3.72 (s, 2 H) ppm. 13C
NMR (126 MHz, CDCl3): δ = 170.9, 139.3, 132.5, 130.3, 118.8,
111.3, 52.5, 41.2 ppm. MS (ESI): m/z = 176 [M + 1]+. C6H9NO2
(127.14): calcd. C 68.56, H 5.18, N 8.00; found C 68.39, H 6.33, N
7.75,
Isopropyl 2-(4-Nitrophenyl)acetate (3q): Light yellow solid (73 mg,
1
65% yield); m.p. 32–34 °C. H NMR (400 MHz, CDCl3): δ = 8.15
(d, J = 8.4 Hz, 2 H), 7.45 (d, J = 8.4 Hz, 2 H), 5.01 (dt, J = 12.5,
6.3 Hz, 1 H), 3.69 (s, 2 H), 1.22 (d, J = 6.3 Hz, 6 H) ppm. 13C
NMR (101 MHz, CDCl3): δ = 169.6, 147.1, 141.7, 130.2, 123.6,
68.8, 41.3, 21.7 ppm. MS (ESI): m/z = 224 [M + 1]+. C12H15NO4
(237.25): calcd. C 59.19, H 5.87, N 6.27; found C 59.54, H 5.63, N
6.11.
Ethyl 4-(2-Methoxy-2-oxoethyl)benzoate (3f): Light yellow oil
1
(89 mg, 80% yield). H NMR (500 MHz, CDCl3): δ = 7.98 (d, J =
8.2 Hz, 2 H), 7.33 (d, J = 8.2 Hz, 2 H), 4.35 (q, J = 7.1 Hz, 2 H),
3.68 (s, 3 H), 3.66 (s, 2 H), 1.36 (t, J = 7.1 Hz, 3 H) ppm. 13C NMR
(126 MHz, CDCl3): δ = 171.4, 166.5, 139.0, 130.0, 129.0, 61.1, 52.3,
41.2, 14.4 ppm. MS (ESI): m/z = 223 [M + 1]+. C12H14O4 (222.24):
calcd. C 64.85, H 6.35; found C 64.70, H 6.51.
2,2,2-Trifluoroethyl 2-(4-Nitrophenyl)acetate (3r): Light yellow oil
1
(68 mg, 52% yield). H NMR (500 MHz, CDCl3): δ = 8.20 (d, J =
8.7 Hz, 2 H), 7.48 (d, J = 8.6 Hz, 2 H), 4.52 (q, J = 8.4 Hz, 2 H),
3.86 (s, 2 H) ppm. 13C NMR (126 MHz, CDCl3): δ = 168.8, 147.5,
140.1, 130.5, 124.0, 121.7, 61.4, 61.1, 60.8, 60.6, 40.2 ppm. MS
(ESI): m/z = 264 [M + 1]+. C12H15NO4 (237.25): calcd. C 45.64, H
3.06, N 5.32; found C 45.95, H 3.22, N 5.03.
Methyl 2-(4-Chlorophenyl)acetate (3g): Light yellow oil (30 mg,
33% yield). H NMR (500 MHz, CDCl3): δ = 7.30 (d, J = 8.5 Hz,
2 H), 7.22 (d, J = 8.4 Hz, 2 H), 3.70 (s, 3 H), 3.60 (s, 2 H) ppm.
13C NMR (126 MHz, CDCl3): δ = 171.7, 133.2, 132.5, 130.8, 128.8,
52.3, 40.5 ppm. MS (ESI): m/z = 185 [M + 1]+. C9H9ClO2 (184.62):
calcd. C 58.55, H 4.91; found C 58.76, H 4.68.
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Preparation of Oxindoles 5: Compound 3b or 3i (0.1 g) and 10%
Methyl 3-(2-Methoxy-2-oxoethyl)thiophene-2-carboxylate (3h): Pd/C (30 mg) were dissolved in ethyl acetate (2 mL) in a sealed tube
1
Light yellow oil (75 mg, 71% yield). H NMR (500 MHz, CDCl3): at room temperature under H2 (initial pressure: 3 atm). After the
Eur. J. Org. Chem. 2015, 5775–5780
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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