BAYINDIR et al./Turk J Chem
112.3, 110.2, 105.5, 74.1, 25.1, 24.6; IR (KBr, cm−1): 3426, 3403, 3342, 3036, 2918, 2876, 2851, 2725, 2685,
1714, 1605, 1469, 1208, 870, 740; Anal. Calcd. for C16 H14 N2 O2 : C, 72.17; H, 5.30; N, 10.52; found: C, 72.57;
H, 5.31; N, 10.97; TLC: Rf = 0.12 (EtOAc/hexane (v/v: 1/3), 254 nm).
3.3. The oxidation of 3-(4,7-dihydro-1H -indol-2-yl)-3-hydroxy indolin-2-one (5)
Procedure A: To a solution of 3-(4,7-dihydro-1H -indol-2-yl)-3-hydroxyindolin-2-one (5, 300 mg, 1.13 mmol)
in 10 mL of CH2 Cl2 was added MnO2 (980 mg, 11.3 mmol). After stirring for 12 h at room temperature, the
mixture was diluted with EtOAc (30 mL) and washed with water (3 × 30 mL), and the organic phase was dried
over Na2 SO4 . The crude product (230 mg) was eluted on silica gel (25 g) with EtOAc/hexane (v/v: 3/7).
After purification, (2-aminophenyl)(1H -indol-2-yl)methanone (7, 215 mg, 81%) was obtained as a white solid
(mp: 115–116 ◦ C (crystallized over CH2 Cl2 / hexane)).
Procedure B: (2-Aminophenyl)(1H -indol-2-yl)methanone (7) was obtained as a white solid (67 mg,
25%) from the reaction of 3-(4,7-dihydro-1H -indol-2-yl)-3-hydroxyindolin-2-one (5, 300 mg, 1.13 mmol) with
p-benzoquinone (304 mg, 2.82 mmol) in CH2 Cl2 at room temperature for 12 h.
Procedure C: (2-Aminophenyl)(1H-indol-2-yl)methanone (7) was obtained as a white solid (32 mg,
12%) from the reaction of 3-(4,7-dihydro-1H -indol-2-yl)-3-hydroxyindolin-2-one (5, 300 mg, 1.13 mmol) with
DDQ (640 mg, 2.82 mmol) in CH2 Cl2 at room temperature for 12 h.
1 H NMR (400 MHz, CDCl3): δ 9.29 (bs, NH, 1H), 8.01 (d, J = 8.1 Hz, =CH, 1H), 7.71 (d, J = 7.3
Hz, =CH, 1H), 7.45 (d, J = 8.1 Hz, =CH, 1H), 7.36–7.31 (m, =CH, 2H), 7.16 (t, J = 7.3 Hz, =CH, 1H),
7.11 (s, =CH, 1H), 6.78–7.74 (m, =CH, 2H), 5.71 (s, NH2 , 2H); 13 C NMR (100 MHz, CDCl3): δ 177.0, 149.7,
137.0, 135.2, 133.8, 132.5, 127.8, 126.0, 123.0, 120.9, 119.3, 117.0, 116.2, 112.0, 111.7; IR (KBr, cm−1): 3437,
3401, 3038, 2918, 2876, 2851, 2725, 1725, 1635, 1424, 1205, 777; Anal. Calcd. for C15 H12 N2 O: C, 76.25; H,
5.12; N, 11.86; found: C, 76.37; H, 5.11; N, 11.97; TLC: Rf = 0.32 (EtOAc/hexane (v/v: 3/7), 254 nm).
3.4. The reaction of 4,7-dihydro-1H -indole (2, 2 equiv.) with isatin (4, 1 equiv.)
To a solution of 4,7-dihydro-1H -indole (2; 300 mg, 2.50 mmol) in MeCN (5 mL) was added isatin (4, 185 mg,
1.26 mmol) and Bi(NO3).3 5H2 O (0.1 mmol). The reaction mixture was stirred magnetically in a flask at 100 ◦ C.
The reaction was monitored by TLC. After the completion of the reaction, the mixture was diluted with ethyl
acetate (30 mL) and washed with water (2 × 50 mL), and the organic phase was dried over Na2 SO4 . The crude
product was dissolved in CH2 Cl2 (15 mL) and p-benzoquinone (330 mg, 3.06 mmol) was added. The mixture
was stirred at room temperature overnight. After completion of the reaction, the solvent was evaporated, the
crude product was dissolved with ethyl acetate (30 mL), and the organic phase was washed with NaOH (2 N,
2 × 30 mL) and brine (30 mL) and dried over Na2 SO4 . The crude product was purified by silica gel column
chromatography and isolated compounds was given according to elution sequence (EtOAc/hexane; v/v: 3/17).
After purification, 1H ,1′′H -[2,3′ :3′ ,2′′ -terindol]-2′ (1′ H)-one (12, 382 mg, 85%) was obtained as a pale red
solid (mp: 137–138 ◦ C (crystallized over CH2 Cl2 /hexane)).
1 H NMR (400 MHz, CDCl3): δ 8.76 (bs, NH, 2H), 8.30 (bs, NH, 1H), 7.60 (d, J = 7.6 Hz, =CH, 1H),
7.52 (d, J = 7.6 Hz, =CH, 2H), 7.33–7.26 (m, =CH, 3H), 7.20–7.13 (m, =CH, 3H), 7.06 (t, J = 7.6 Hz, =CH,
2H), 6.99 (d, J = 7.6 Hz, =CH, 1H), 6.42 (s, =CH, 2H); 13 C NMR (100 MHz, CDCl3): δ 177.0, 140.3, 136.8,
135.1, 130.8, 129.4, 128.0, 126.1, 123.6, 122.7, 120.9, 120.4, 111.4, 110.9, 102.4, 79.3; IR (KBr, cm−1): 3451,
342