1318
R. Bujok et al.
LETTER
[M+], 152 (1), 135 (100), 107 (4), 92 (7), 77 (10). ESI-
HRMS: m/z calcd for C15H12N2O6Na: 339.0588; found:
339.0590.
(6) Preston, P. N.; Tennant, G. Chem. Rev. 1972, 72, 627.
(7) (a) Wróbel, Z.; Mąkosza, M. Synlett 1993, 597. (b) Wróbel,
Z.; Mąkosza, M. Tetrahedron 1993, 49, 5315.
(8) Camara, H. D.; Attar, K.; Benchidmi, M.; Essassi, E. M.;
Garriques, B. Indian J. Chem., Sect. B: Org. Chem. Incl.
Med. Chem. 2004, 43, 660.
(9) Wong, A.; Kuethe, J. T.; Davies, I. W. J. Org. Chem. 2003,
68, 9865.
(10) (a) Bunce, R. A.; Nammalwar, B. J. Heterocycl. Chem.
2009, 46, 172. (b) Prüger, B.; Hofmeister, G.; Jacobsen, C.
B.; Alberg, D. G.; Nielsen, M.; Jørgensen, K. A. Chem.–Eur.
J. 2010, 16, 3783.
(14) 1-Hydroxy-nitroindoles from Dinitrobenzyl Ketones –
General Procedure
To dinitrobenzyl ketone (2 mmol) dissolved in EtOAc (10
mL) and EtOH (1 mL) SnCl2 (1.44 g, 7.6 mmol) was added
in one portion. The reaction mixture was stirred overnight at
r.t. The reaction mixture was then evaporated, and the
residue was subjected to column chromatography on silica
gel. The product was eluted with EtOAc–hexane (4:1). The
following compounds were obtained.
(11) For reviews, see: (a) Mąkosza, M. Chem. Soc. Rev. 2010, 39,
2855. (b) Mąkosza, M.; Wojciechowski, K. Chem. Rev.
2004, 104, 2631. (c) Mąkosza, M.; Wojciechowski, K.
Heterocycles 2001, 54, 445.
(12) Wróbel, Z.; Mąkosza, M. Pol. J. Chem. 1992, 66, 2005.
(13) General Procedure for the Synthesis of Dinitrobenzyl
Ketones 4a–f
1-Hydroxy-2-methyl-6-nitroindole (4a)
Orange crystals, mp 153–155 °C. 1H NMR [500 MHz,
(CD3)2CO]: δ = 2.51 (d, J = 1.0 Hz, 3 H), 6.32 (q, J = 1.0 Hz,
1 H), 7.58 (d, J = 8.8 Hz, 1 H), 7.89 (dd, J = 8.8, 2.2 Hz‚ 1
H), 8.28 (d, J = 2.2 Hz, 1 H), 10.49 (br s, 1 H). 13C NMR [125
MHz, (CD3)2CO]: δ = 11.34, 97.21, 105.24, 115.22, 120.36,
129.22, 133.19, 142.35, 142.98. IR (KBr): ν = 3261, 1609,
1583, 1505, 1458, 1392, 1365, 1326, 1276, 1220, 1134, 865,
762 cm–1. MS (EI, 70 eV): m/z (%) = 192 (100) [M+], 191
(10), 176 (22), 162 (7), 146 (32), 145 (15)130 (12), 129 (23),
128 (16), 117 (23), 103 (16), 102 (17). HRMS (EI): m/z calcd
for C9H8N2O3: 192.0535; found: 192.0541.
To a stirred solution of 1,3-dinitrobenzene (10 mmol) and α-
chloromethyl ketone (2, 10 mmol) in DMF (25 mL) cooled
to –20 °C was added DBU (5.32 g, 5.2 mL, 35 mmol). The
stirring was continued for 40 min allowing the reaction
mixture to reach r.t. Then the reaction mixture was stirred for
additional 20 min and poured into diluted HCl (100 mL).
The precipitate was filtered, diluted with EtOAc (50 mL),
washed with brine, and dried with Na2SO4. After
evaporation of the solvent the residue was chromatographed
on silica gel with EtOAc–hexane (2:1). The following
compounds were obtained.
2-tert-Butyl-1-hydroxy-6-nitroindole (4b)
Orange crystals, mp 147–149 °C. 1H NMR [500 MHz,
(CD3)2CO]: δ = 1.51 (s, 9 H), 6.32 (d, J = 0.9 Hz, 1 H), 7.61
(dd, J = 8.6, 0.6 Hz, 1 H), 7.89 (dd, J = 8.7, 2.1 Hz, 1 H), 8.26
(br d, J = 2.2 Hz, 1 H), 10.64 (br s, 1 H). 13C NMR [125
MHz, (CD3)2CO]: δ = 29.23, 33.33, 95.00, 96.62, 105.29,
115.19, 120.78, 128.44, 134.52, 143.20, 153.52. MS (EI, 70
eV): m/z (%) = 234 (71) [M+], 219 (100), 203 (12), 202 (13),
201 (17), 173 (13), 172 (12), 156 (13), 155 (15). HRMS (EI):
m/z calcd for C12H14N2O3: 234.1004, found: 234.0997.
1-Hydroxy-2-phenyl-6-nitroindole (4c)
1-(2,4-Dinitrophenyl)-propan-2-one (3a)
Pale yellow crystals, mp 65–67 °C (lit. 12 66–67 °C).
1-(2,4-Dinitrophenyl)-3,3-dimethylbutan-2-one (3b)
Orange crystals, mp 60–62 °C. 1H NMR (500 MHz, CDCl3):
δ = 1.20 (s, 9 H), 4.24 (s, 2 H), 7.47 (d, J = 8.3 Hz, 1 H), 8.40
(dd, J = 8.3, 2.3 Hz, 1 H), 8.94 (d, J = 2.3 Hz, 1 H). 13C NMR
(125 MHz, CDCl3): δ = 26.59, 42.70, 44.45, 120.54, 127.09,
128.86, 134.69, 137.92, 147.14, 149.25, 209.54. ESI-MS:
m/z = 555 [2M + Na+], 289 [M + Na+]. ESI-HRMS: m/z calcd
for C12H14N2O5Na: 289.0795; found: 289.0786.
Red-orange crystals, mp 158–160 °C. 1H NMR [500 MHz,
(CD3)2CO]: δ = 6.84 (s, 1 H), 7.45–7.50 (m, 1 H), 7.51–7.56
(m, 2 H), 7.74 (d, J = 8.7 Hz, 1 H), 7.95–7.99 (m, 3 H), 8.41
(d, J = 2.1 Hz, 1 H), 10.72 (br s, 1 H). 13C NMR [125 MHz,
(CD3)2CO]: δ = 97.52, 105.31, 115.06, 120.57, 128.11,
128.36, 128.72, 128.94, 129.94, 134.13, 143.03, 143.08. IR
(KBr): ν = 3247, 1607, 1501, 1478, 1467, 1316, 1273, 1081,
818, 763 cm–1. MS (EI, 70 eV): m/z (%) = 254 (100) [M+],
238 (25), 225 (11), 224 (10), 208 (24), 207 (17), 191 (23),
190 (38), 180 (17), 179 (50), 165 10), 164 (10), 163 (11), 152
(10). HRMS (EI): m/z calcd for C14H10N2O3: 254.0691;
found: 254.0695.
2-(4-Chlorophenyl)-1-hydroxy-6-nitroindole (4d)
Orange crystals, mp 201–203 °C. 1H NMR [500 MHz,
(CD3)2CO]: δ = 6.86 (d, J = 1.0 Hz, 1 H), 7.54–7.58 (m, 2 H),
7.73 (d, J = 8.7 Hz, 1 H), 7.96 (dd, J = 8.7, 2.1 Hz, 1 H),
7.97–8.00 (m, 2 H), 8.38 (br d, 2.1 Hz, 1 H), 10.81 (br s, 1
H). 13C NMR [125 MHz, (CD3)2CO]: δ = 98.70, 106.24,
116.01, 121.61, 128.81, 129.58, 129.73, 130.72, 135.06,
135.26, 142.48, 144.09. IR (KBr): ν = 3278, 1608, 1536,
1506, 1479, 1336, 1286, 1279, 1084, 813, 773, 761, 726 cm–1.
MS (EI, 70 eV): m/z (%) = 280 (57) [M+], 270 (100), 258
(20), 242 (35), 213 (36), 206 (15), 191 (45), 190 (60), 178
(22). HRMS (EI): m/z calcd for C14H935ClN2O3: 288.0302;
found: 288.0299.
1-(2,4-Dinitrophenyl)-2-phenylethanone (3c)
Pale yellow crystals, mp 133–135 °C (lit.12 136–137 °C). 1H
NMR (500 MHz, CDCl3): δ = 4.87 (s, 2 H), 7.51–7.55 (m, 2
H), 7.59 (d, J = 8.5 Hz, 1 H), 7.63–7.68 (m, 2 H), 8.01–8.04
(m, 2 H), 8.46 (dd, J = 8.5, 2.2 Hz, 1 H), 8.98 (d, J = 2.2 Hz,
1 H). 13C NMR (125 MHz, CDCl3): δ = 44.14, 120.68,
127.32, 128.27, 128.92, 134.01, 134.93, 135.87, 137.56,
147.37, 149.23, 193.86. ESI-MS: m/z = 309 [M + Na+]. ESI-
HRMS: m/z calcd for C14H10N2O5Na: 309.0482; found:
309.0497.
1-(4-Chlorophenyl)-2-(2,4-dinitrophenyl)-ethanone (3d)
Yellow crystals, mp 145–147 °C. 1H NMR (500 MHz,
CDCl3): δ = 4.83 (s, 2 H), 7.50–7.53 (m, 2 H), 7.59 (d, J =
8.4 Hz, 1 H), 7.95–7.99 (m, 2 H), 8.47 (dd, J = 8.4, 2.4 Hz,
1 H), 9.00 (d, J = 2.4 Hz, 1 H). 13C NMR (125 MHz, CDCl3):
δ = 44.09, 120.75, 127.42, 129.28, 129.66, 134.18, 134.94,
137.17, 140.60, 147.47, 149.09, 192.75. ESI-HRMS: m/z
calcd for C14H9N2O5ClNa: 343.0092; found: 343.0106.
1-(2,4-Dinitrophenyl)-2-(4-methoxyphenyl)ethanone
(3e)
Yellow crystals, mp 102–103 °C (lit.10b 102–105 °C). 1H
NMR (500 MHz, CDCl3): δ = 3.90 (s, 3 H), 4.82 (s, 2 H),
6.97–7.01 (m, 2 H), 7.58 (d, J = 8.4 Hz, 1 H), 7.98–8.02 (m,
2 H), 8.43 (dd, J = 8.4, 2.3 Hz, 1 H), 8.97 (d, J = 2.3 Hz, 1
H). 13C NMR (125 MHz, CDCl3): δ = 43.70, 55.58, 114.06,
120.57, 127.19, 128.86, 130.62, 134.88, 137.86, 147.25,
149.30, 164.19, 192.21. MS (EI, 70 eV): m/z (%) = 316 (2)
1-Hydroxy-2-(4-methoxyphenyl)-6-nitroindole (4e)
Red-orange crystals, mp 183–185 °C. 1H NMR [500 MHz,
(CD3)2CO]: δ = 3.88 (s, 3 H), 6.74 (d, J = 1.0 Hz, 1 H), 7.07–
7.11 (m, 2 H), 7.69 (d, J = 8.7 Hz, 1 H), 7.90–7.94 (m, 2 H),
7.96 (dd, J = 8.5, 2.0 Hz, 1 H), 8.37 (br d, J = 2.0 Hz, 1H),
10.70 (s, 1 H). 13C NMR [125 MHz, (CD3)2CO]: δ = 54.84,
96.44, 105.10, 114.17, 115.04, 120.11, 122.26, 128.31,
Synlett 2012, 23, 1315–1320
© Georg Thieme Verlag Stuttgart · New York