The Journal of Organic Chemistry
Note
2.74 (s, 3H), 2.84 (s, 3H), 6.69 (d, J = 3.8 Hz, 1H), 7.43−7.54 (m,
3H), 7.70 (d, J = 3.8, 1H), 7.85 (s, 1H), 8.59−8.64 (m, 1H); 13C
NMR (50 MHz, CDCl3−CF3COOD): δ = 12.5, 14.5, 114.2, 115.1,
122.0 (q), 123.8 (q), 124.5, 127.3, 128.8, 134.2, 137.5, 138.8 (q), 149.9
(q), 168.0 (q), 169.4 (q); IR (CHCl3) νmax 3032, 3012, 1577, 1427,
1238, 1198; exact ESI full mass: found m/z 224.16 (calcd for
C15H14NO: M+, m/z 224.11); Anal. Calcd for C15H14BF4NO: C,
57.91; H, 4.54; N, 4.50. Found C, 57.72; H, 4.52; N, 4.52.
(q), 142.8, 156.7 (q); IR (CHCl3) νmax 3331, 3026, 3017, 1621, 1509,
1403, 1225, 1218, 1209; exact ESI full mass: found m/z 187.12 (calcd
for C12H15N2: M+, m/z 187.12); Anal. Calcd for C12H15BF4N2: C,
52.59; H, 5.52; N, 10.22; Found C, 52.44; H, 5.50; N, 10.24.
(3,5-Dimethyl-2-pyrrolyl)(3-indolyl)methylium Tetrafluoroborate
(3l). (0.78 g, 84% yield); dp 216 °C (anhydrous MeCN/anhydrous
1
Et2O); H NMR (200 MHz, CDCl3−CF3COOD): δ = 2.46 (s, 3H),
2.54 (s, 3H), 6.40 (s, 1H), 7.35−7.42 (m, 2H), 7.45−7.55 (m, 1H),
7.77−7.85 (m, 1H), 7.99 (s, 1H), 8.50 (s, 1H); 13C NMR (50 MHz,
CDCl3−CF3COOD): δ = 11.5, 13.9, 113.2 (q), 113.4, 118.0, 120.1,
124.6, 125.8, 127.0 (q), 132.5, 133.1 (q), 136.7 (q), 137.8, 147.1 (q),
151.6 (q); IR (CHCl3) νmax 3032, 3012, 1583, 1237, 1198; exact ESI
full mass: found m/z 213.17 (calcd for C15H15N2: M+, m/z 223.12);
Anal. Calcd for C15H15BF4N2: C, 58.10; H, 4.88; N, 9.03; Found C,
58.15; H, 4.86; N, 9.04.
(2-Methyl-3-indolyl)(4-nitrophenyl)methylium Tetrafluoroborate
(3f). (0.89 g, 84% yield); dp 200 °C (anhydrous MeCN/anhydrous
1
Et2O); H NMR (200 MHz, CDCl3−CF3COOD): δ = 3.02 (s, 3H),
7.35−7.43 (m, 1H), 7.50−7.61 (m, 2H), 7.79 (d, J = 7.6 Hz, 1H), 8.03
(d, J = 8.8, 2H), 8.44 (d, J = 8.8, 2H), 8.56 (s, 1H); 13C NMR (50
MHz, CDCl3−CF3COOD): δ = 13.3, 116.0, 123.0 (q), 123.5, 124.3
(2C), 129.3, 131.3 (2C), 131.8, 134.3 (q), 138.4 (q), 140.4 (q), 149.5
(q), 152.9, 174.7 (q); IR (CHCl3) νmax 3033, 3012, 1640, 1235, 1197;
exact ESI full mass: found m/z 265.07 (calcd for C16H13N2O2: M+, m/
z 265.10); Anal. Calcd for C16H13BF4N2O2: C, 54.58; H, 3.72; N, 7.96;
Found C, 54.40; H, 3.71; N, 7.98.
General Procedure for Diarylmethylium Tetrafluoroborates 3a−l
Reduction. NaBH4 (1.0 mmol, 0.04 g) was added portionwise at rt
and under stirring to a solution of salt 3 (1.0 mmol) in anhydrous
MeCN (15 mL). The reaction was instantaneous, and the deeply
colored solution immediately faded. After stirring at rt for 10 min, the
reaction mixture was treated with Et2O/water (40 mL; 1:1). The
organic phase was separated, washed with brine (2 × 20 mL), and
evaporated under reduced pressure. The crude residue was the
(1,2-Dimethyl-3-indolyl)(4-nitrophenyl)methylium Tetrafluoro-
borate (3g). (1.04 g, 95% yield); dp 218 °C (anhydrous MeCN/
1
anhydrous Et2O); H NMR (200 MHz, CDCl3−CF3COOD): δ =
2.96 (s, 3H), 4.01 (s, 3H), 7.36−7.44 (m, 1H), 7.53−7.64 (m, 2H),
7.95 (d, J = 8.8, 2H), 8.39 (d, J = 8.8, 2H), 8.56 (s, 1H); 13C NMR (50
MHz, CDCl3−CF3COOD): δ = 12.1, 33.4, 113.8, 123.0 (q), 123.6,
124.3 (2C), 129.6, 131.2 (2C), 131.5, 133.8 (q), 138.6 (q), 143.0 (q),
149.4 (q), 152.2, 173.2 (q); IR (CHCl3) νmax 3032, 3012, 1534, 1238,
1198; exact ESI full mass: found m/z 279.11 (calcd for C17H15N2O2:
M+, m/z 279.11); Anal. Calcd for C17H15BF4N2O2: C, 55.77; H, 4.13;
N, 7.65; Found C, 55.69; H, 4.14; N, 7.62.
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virtually pure reduction product 4 (GC, GC−MS, H NMR), which
was, however, purified via short column chromatography (eluent PE/
EE 6/4); yields of purified products are reported in Table 1. Structure
and purity of products 4a−e were confirmed by comparing physical
and spectral data (MS, 1H NMR, and 13C NMR) with previously
reported data;13 yields and physical and spectroscopic data are listed
below for new products 4f−l.
(4-Nitrophenyl)(2-methyl-3-indolyl)methane (4f).31 Yellow solid
(0.22 g, 83% yield); mp 123.0−124.0 °C (DCM−PE); 1H NMR (200
MHz, CDCl3): δ = 2.34 (s, 3H), 4.10 (s, 2H), 6.97−7.11 (m, 2H),
7.20−7.24 (m,2H), 7.29 (d, J = 8.8 Hz, 2H), 7.83 (br s, 1H), 8.03 (d, J
= 8.8 Hz, 2H); 13C NMR (50 MHz, CDCl3): δ = 11.6, 29.9, 108.7 (q),
110.2, 117.7, 119.4, 121.2, 123.4 (2C), 128.2 (q), 128.8 (2C), 131.8
(q), 135.1 (q), 146.0 (q), 149.3 (q); IR (CHCl3) νmax 3471, 3009,
2921, 1599, 1518, 1461, 1347, 1068; MS m/z (%): 266 [M+](100),
144 (85).
(4-N,N-Dimethylaminophenyl)(1,2-dimethyl-3-indolyl)methylium
Tetrafluoroborate (3h). (1.06 g, 97% yield); dp 178 °C (anhydrous
MeCN/anhydrous Et2O); 1H NMR (200 MHz, CDCl3−CF3COOD):
δ = 2.96 (s, 3H), 3.45 (s, 6H), 4.03 (s, 3H), 7.41−7.49 (m, 1H), 7.55−
7.68 (m, 2H), 7.83 (d, J = 8.8 Hz, 1H) overlapped with 7.80−7.88 (m,
1H), 8.05 (d, J = 8.6, 2H), 8.54 (s, 1H); 13C NMR (50 MHz, CDCl3−
CF3COOD): δ = 11.7, 33.0, 47.2 (2C), 113.6, 121.2 (2C), 122.8 (q),
123.4, 129.7, 131.5, 132.9 (2C), 133.4 (q), 135.2 (q), 142.9 (q), 144.3
(q), 152.1, 172.8 (q); IR (CHCl3) νmax 3026, 3016, 1615, 1574, 1513,
1376, 1327, 1174; exact ESI full mass: found m/z 277.22 (calcd for
C19H21N2: M+, m/z 277.17); Anal. Calcd for C19H21BF4N2: C, 62.66;
H, 5.81; N, 7.69. Found C, 62.70; H, 5.79; N, 7.71.
(2,5-Dimethyl-3-pyrrolyl)(4-methoxyphenyl)methylium Tetra-
fluoroborate (3i). (0.63 g, 70% yield); dp 182 °C (anhydrous
MeCN/anhydrous Et2O); 1H NMR (200 MHz, CDCl3−CF3COOD):
δ = 2.29 (s, 3H), 2.72 (s, 3H), 3.96 (s, 3H), 6.69 (br s, 1H), 7.11 (d, J
= 9.0, 2H), 7.98 (d, J = 9.0, 2H), 8.19 (s, 1H); 13C NMR (50 MHz,
CDCl3−CF3COOD): δ = 11.4, 11.7, 55.6, 108.8, 116.1 (2C), 126.6
(q), 130.3 (q), 138.4 (2C), 141.6 (q), 158.5, 164.9 (q), 167.9 (q); IR
(CHCl3) νmax 3026, 3018, 1582, 1512, 1328, 1275, 1233, 1212, 1200;
exact ESI full mass: found m/z 214.15 (calcd for C14H16NO: M+, m/z
214.12); Anal. Calcd for C14H16BF4NO: C, 55.85; H, 5.36; N, 4.65;
Found C, 55.71; H, 5.33; N, 4.66.
(4-Nitrophenyl)(1,2-dimethyl-3-indolyl)methane (4g). Yellow
solid (0.27 g, 93% yield); mp 114.0−115.0 °C (DCM−PE); 1H
NMR (200 MHz, CDCl3): δ = 2.34 (s, 3H), 3.65 (3H), 4.14 (s, 2H),
6.95−7.08 (m, 2H), 7.10−7.28 (m, 2H), 7.29 (d, J = 8.8 Hz, 2H), 8.03
(d, J = 8.8 Hz, 2H); 13C NMR (50 MHz, CDCl3): δ = 10.2, 29.5, 30.2,
107.9 (q), 108.6, 117.7, 119.0, 120.8, 123.4 (2C), 127.3 (q), 128.7
(2C), 133.7 (q), 136.5 (q), 146.0 (q), 149.6 (q); IR (CHCl3) νmax
3468, 3029, 2943, 1597, 1521, 1474, 1347, 1068; MS m/z (%): 280
[M+](100), 158 (100); Anal. Calcd for C17H16N2O2: C, 72.84; H,
5.75; N, 9.99; Found C, 72.70; H, 5.77; N, 9.96.
(4-N,N-Dimethylaminophenyl)(1,2-dimethyl-3-indolyl)methane
(4h). Light pink solid (0.24 g, 86% yield); mp 128.0−129.0 °C
(DCM−PE); 1H NMR (200 MHz, CDCl3): δ = 2.36 (s, 3H), 2.87 (s,
6H), 3.64 (s, 3H), 4.02 (s, 2H), 6.65 (d, J = 8.6 Hz, 2H), 7.01−7.15
(m, 2H) overlapped with 7.10 (d, J = 8.8 Hz, 2H), 7.17−7.28 (m, 1H),
7.46 (d, J = 7.6 Hz, 1H); 13C NMR (50 MHz, CDCl3): δ = 10.2, 29.2,
29.4, 40.8 (2C), 108.3, 110.3 (q), 112.9 (2C), 118.3, 118.6, 120.3,
127.9 (q), 128.6 (2C), 130.2 (q), 133.1 (q), 136.5 (q), 148.8 (q); IR
(CHCl3) νmax 3467, 3029, 3022, 3011, 2943, 1614, 1519, 1473, 1236,
1198, 1066; MS m/z (%): 278 [M+](100), 263 (100); Anal. Calcd for
C19H22N2: C, 81.97; H, 7.97; N, 10.06; Found C, 81.78; H, 7.95; N,
10.02.
(2,5-Dimethyl-3-pyrrolyl)(3-indolyl)methylium Tetrafluoroborate
(3j). (0.85 g, 91% yield); dp 174 °C (anhydrous MeCN/anhydrous
1
Et2O); H NMR (200 MHz, CDCl3−CF3COOD): δ = 2.21 (s, 3H),
2.58 (s, 3H), 7.31−77.45 (m, 1H), 7.48−7.54 (m, 2H), 7.80−7.85 (m,
1H), 8.30 (s, 1H), 8.46 (s, 1H); 13C NMR (50 MHz, CDCl3−
CF3COOD): δ = 11.4, 11.7, 107.7, 113.8, 118.0 (q), 118.3 (q), 125.0
(q), 125.5 (2C), 126.3, 137.4 (q), 137.6 (q), 148.2 (q), 155.8 (q),
156.0 (q); IR (CHCl3) νmax 3025, 3014, 1580, 1334, 1295, 1225; exact
ESI full mass: found m/z 213.16 (calcd for C15H15N2: M+, m/z
223.12); Anal. Calcd for C15H15BF4N2: C, 58.10; H, 4.88; N, 9.03;
Found C, 58.15; H, 4.85; N, 9.00.
(2,5-Dimethyl-3-pyrrolyl)(4-methoxyphenyl)methane (4i). Oil
(0.10 g, 47% yield); 1H NMR (200 MHz, CDCl3): δ = 2.17 (s,
3H), 2.19 (s, 3H), 3.69 (s, 2H), 3.80 (s, 3H), 5.60−5.65 (m, 1H), 6.84
(d, J = 8.8 Hz, 2H), 7.15 (d, J = 8.8 Hz, 2H), 7.48 (br s, 1H); 13C
NMR (50 MHz, CDCl3): δ = 10.9, 12.9, 31.3, 55.1, 106.9, 113.6 (2C),
118.3 (q), 121.8 (q), 124.9 (q), 129.2 (2C), 134.9 (q), 160.4 (q); IR
(CHCl3) νmax 3443, 3020, 3006, 2935, 1611, 1511, 1465, 1248, 1201,
1177; MS m/z (%): 215 [M+](100), 200 (75), 108 (60). Anal. Calcd
(2,5-Dimethyl-3-pyrrolyl)(1-methyl-2-pyrrolyl)methylium Tetra-
fluoroborate (3k). (0.82 g, quantitative yield); dp 208 °C (anhydrous
MeCN/anhydrous Et2O); 1H NMR (200 MHz, CDCl3−CF3COOD):
δ = 2.21 (s, 3H), 2.56 (s, 3H), 3.88 (s, 3H), 6.63 (br s, 1H), 7.48−7.62
(m, 2H), 7.81 (s, 1H); 13C NMR (50 MHz, CDCl3−CF3COOD): δ =
11.2, 11.7, 34.4, 117.8, 123.6 (q), 129.2, 133.2 (q), 137.8 (2C), 138.2
E
J. Org. Chem. XXXX, XXX, XXX−XXX