Beilstein J. Org. Chem. 2013, 9, 1873–1880.
Photocyclization and preparation of salts 1.
3
H), 2.98 (s, 3H), 4.97 (d, J = 5.0 Hz, 2H), 5.92 (t, J = 5.5 Hz,
1H), 7.14 (d, J = 7.8 Hz, 2H), 7.50 (d, J = 8.0 Hz, 2H), 8.49 (d,
Method A [7]: Azo compound 4 (1.0 mmol) and calcium J = 8.5 Hz, 1H), 8.64 (d, J = 5.5 Hz, 1H), 8.95 (s, 1H), 9.17 (d,
p-toluenesulfonate (190 mg 0.5 mmol) or calcium chloride J = 8.9 Hz, 1H), 9.35 (s, 1H), 10.36 (d, J = 6.8 Hz, 1H);
(
(
56 mg, 0.5 mmol) were dissolved in a mixture of MeCN/H2O 13C NMR (100 MHz, DMSO-d6) δ 20.8, 21.6, 61.6, 116.4,
9:1, 30 mL). The resulted solution was irradiated with a 500 W 121.8, 125.5, 128.0, 128.1, 129.6, 130.2, 131.9, 136.6, 137.6,
halogen lamp and gently refluxed until TLC control showed full 141.2, 142.0, 145.7, 148.2, 159.2; anal. calcd for
conversion of the substrate (about 1.5 h). The solvents were C20H19N3O4S: C, 60.44; H, 4.82; N, 10.57; found: C, 60.15; H,
evaporated. The residue was dried in a desiccator over P2O5 4.78; N, 10.47.
(
12 h). The solid was washed with CH2Cl2, the residue was
dissolved in hot MeCN and filtered. The solvent was evapo- Azo compounds 4. A general procedure
rated and the crude product was recrystallized from aqueous Method A. To the solution of amine (1.0 mmol) in dry CH2Cl2
MeCN.
(2 mL), 2-nitroso-4-picoline (7, 1.0 mmol) was added followed
by a catalytic amount (1 drop) of acetic acid. The reaction mix-
Method B: The reaction mixture prepared as in method A was ture was stirred at rt for 24 h, protected from a light. The
exposed to intense sunlight, while stirring until TLC control solvent was evaporated and the residue was purified on a silica
showed full conversion of the substrate (about 1.5 h). The work- gel plug (CH2Cl2/EtOAc, 5:1) to give the corresponding azo
up of the reaction mixture was as described in method A.
compound as orange-red crystals. Analytically pure samples
were obtained by recrystallization (hexane/CH2Cl2).
3
-Methylpyrido[2,1-c][1,2,4]benzotriazin-11-ium p-toluene-
sulfonate (1b): Method A, yield 95%: 1H NMR (300 MHz, 2-(2-Fluorophenylazo)picoline (4b): Yield: 83%: mp
CD3CN) δ 2.33 (s, 3H), 2.98 (s, 3H), 7.16 (d, J = 7.8 Hz, 2H), 78–80 °C; 1H NMR (300 MHz, CDCl3) δ 2.48 (s, 3H),
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.60 (d, J = 8.0 Hz, 2H), 8.35 (t, J = 7.8 Hz, 1H), 8.43 (d, 7.18–7.34 (m, 3H), 7.48–7.56 (m, 1H), 7.64 (s, 1H), 7.90 (t,
J = 7.5 Hz, 1H), 8.49 (t, J = 8.1 Hz, 1H), 8.83 (d, J = 8.8 Hz, J = 7.7 Hz, 1H), 8.61 (d, J = 4.4 Hz, 1H); 13C NMR (100 MHz,
1
1
1
H), 9.03 (d, J = 8.0 Hz, 1H), 9.12 (s, 1H), 9.87 (d, J = 7.0 Hz, CDCl3) δ 21.2, 114.5, 117.1 (d, J = 20 Hz), 117.9, 124.3 (d,
H); HRMS m/z calcd for C12H10N3, 196.0869; found, J = 4 Hz), 126.5, 133.7 (d, J = 4 Hz), 140.4 (d, J = 6 Hz),
96.0892.
149.3, 149.8, 160.7 (d, J = 258 Hz), 163.3; anal. calcd for
C12H10FN3: C, 66.97; H, 4.68; N, 19.52; found: C, 66.93; H,
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-Fluoro-3-methylpyrido[2,1-c][1,2,4]benzotriazin-11-ium 4.66; N, 19.41.
p-toluenesulfonate (1c): Method B, yield 90%: mp >190 °C
dec.; 1H NMR (300 MHz, CD3CN) δ 2.35 (s, 3H), 2.96 (s, 3H), 2-(2,4-Difluorophenylazo)picoline (4c): Yield 90%: mp
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.19 (d, J = 7.5 Hz, 2H), 7.60 (d, J = 7.1 Hz, 2H), 8.11 (t, 99–101 °C; 1H NMR (300 MHz, CD3CN) δ 2.48 (s, 3H), 7.14
J = 7.8 Hz, 1H), 8.44 (d, J = 6.7 Hz, 1H), 8.64 (dd, J1 = 9.2 Hz, (t, J = 8.8 Hz, 1H), 7.26 (ddd, J1 = 11.3 Hz, J2 = 8.7 Hz,
J2 = 2.2 Hz, 1H), 9.00–9.60 (m, 1H), 9.11 (s, 1H), 9.73 (d, J3 = 2.6 Hz, 1H), 7.37 (d, J = 5.0 Hz, 1H), 7.60 (s, 1H), 7.91
J = 6.8 Hz, 1H); 13C NMR (100 MHz, DMSO-d6) δ 20.8, 21.8, (dd, J1 = 15.3 Hz, J2 = 8.8 Hz, 1H), 8.58 (d, J = 4.8 Hz, 1H);
1
1
1
2
04.1 (d, J = 30 Hz), 121.8 (d, J = 25 Hz), 125.5, 128.0, 129.7, 1H NMR (300 MHz, CDCl3) δ 2.48 (s, 3H), 6.92–7.08 (m, 2H),
30.2, 132.3, 135.7 (d, J = 11 Hz), 137.5, 138.9, 141.9, 145.8, 7.26 (d, 1H), 7.63 (s, 1H), 7.94 (d, J = 8.0 Hz, 1H), 7.99 (d,
60.6; UV–vis (MeCN) λmax (log ε) 225 (4.20), 254 (4.41), J = 8.6 Hz, 1H), 8.60 (d, J = 4.6 Hz, 1H); 13C NMR (100 MHz,
62 sh (4.38), 365 (3.98), 379 sh (3.81); anal. calcd for CDCl3) δ 21.1, 105.1 (t, J = 24 Hz), 112.0 (dd, J1 = 27 Hz,
C19H16FN3O3S: C, 59.21; H, 4.18; N, 10.90; found: C, 58.92; J2 = 4 Hz), 114.5, 119.3 (d, J = 10 Hz), 126.5, 137.3 (dd,
H, 4.09; N, 10.95.
J1 = 7 Hz, J2 = 4 Hz), 149.2, 149.8, 161.2 (dd, J1 = 260 Hz,
J2 = 7 Hz),163.1, 165.3 (dd, J1 = 255 Hz, J2 = 12 Hz); UV–vis
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,9-Difluoro-3-methylpyrido[2,1-c][1,2,4]benzotriazin-11- (MeCN) λmax (log ε) 225 (4.02), 322 (4.22), 541 (6.61); anal.
ium chloride (1d): Method B, yield 40–80% (based on NMR): calcd for C12H9F2N3: C, 61.80; H, 3.89; N, 18.02; found: C,
H NMR (300 MHz, CD3CN) δ 2.98 (s, 3H), 7.99 (t, 61.79; H, 3.79; N, 17.92.
J = 8.1 Hz, 1H), 8.49 (d, J = 5.5 Hz, 1H), 8.56 (d, J = 8.9 Hz,
1
1
H), 9.16 (s, 1H), 9.77 (d, J = 6.8 Hz, 1H).
2-(2,4,6-Trifluorophenylazo)picoline (4d): Yield 38%:
H NMR (300 MHz, CD3CN) δ 2.49 (s, 3H), 6.85 (t,
1
8
1
-Hydroxymethyl-3-methylpyrido[2,1-c][1,2,4]benzotriazin- J = 8.8 Hz, 2H), 7.26 (d, 1H), 7.56 (s, 1H), 8.58 (d, J = 4.9 Hz,
1-ium p-toluenesulfonate (1e): Method A, yield 75%: 1H); 1H NMR (300 MHz, CDCl3) δ 2.48 (s, 3H), 7.09 (t,
mp >150 °C dec.; 1H NMR (300 MHz, DMSO-d6) δ 2.32 (s, J = 9.3 Hz, 2H), 7.26 (d, 1H), 7.61 (s, 1H), 8.61 (d, J = 4.8 Hz,
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