10.1002/ejoc.201801075
European Journal of Organic Chemistry
FULL PAPER
in dichloromethane (50 mL) was added and stirred for further 30 min. at
0 °C. After stirring overnight at room temperature diethyl ether (75 mL) was
added to the reaction mixture and the formed precipitate was filtered off.
The solid was vigorously stirred in pentane (75 mL) and some
dichloromethane (2 – 3 mL) was added to solute the impurities. The
product (16.3 g, 66 %) was obtained as beige solid after filtration. 1H-NMR
(400 MHz, CDCl3): δ (ppm) = 8.16 (s, 1H), 7.92 (d, 3J = 7.5 Hz, 1H), 7.22
– 7.16 (m, 2H), 7.04 (t, J = 7.4 Hz, 1H), 4.86 (t, J = 4.8 Hz, 1H), 3.79 –
3.72 (m, 2H), 3.64 – 3.57 (m, 2H), 2.77 (d, 3J = 4.8 Hz, 2H), 2.27 (s, 3H),
1.25 (t, 3J = 7.1 Hz, 6H). 13C-NMR (100 MHz, CDCl3): δ (ppm) = 167.5,
136.2, 130.4, 128.4, 126.8, 124.8, 122.6, 100.1, 62.9, 43.0, 18.0, 15.4.
δ (ppm) = 158.0, 147.1, 136.6, 136.4, 129.6, 126.5, 125.6, 125.4, 121.7,
25.8, 18.1. HRMS (EI): calcd. for C11H11N+ [M+] 157.0886; found 157.0889.
Bis-(8-methylquinolin-2-yl)methane (23): A 10 mL microwave vessel
was charged with 2-iodo-8-methylquinoline 31 (250 mg, 0.9 mmol) and
2,8-methylquinoline (438 mg, 2.8 mmol). One drop of ethereal
hydrochloric acid (1.0 M in Et2O) was added to the mixture whereby some
precipitate was formed. The vessel was heated for 10 min at 230 °C in a
microwave reactor whereby the slightly yellow mixture turns into dark red.
The waxy mixture was dissolved in dichloromethane, washed with 2 mol/L
sodium hydroxide solution whereby the organic layer turns deep orange.
The dichloromethane was evaporated and the excess of 2,8-
methylquinoline was removed by a Kugelrohr distillation. The product
(165 mg, 59 %) was obtained as a yellow solid by flash chromatography
(pentane:TBME, 10:1 (v/v)). 1H-NMR (400 MHz, CDCl3): δ (ppm) = 8.00 (d,
3J = 8.4 Hz, 2H), 7.61 (d, 3J = 8.1 Hz, 2H), 7.55 (d, 3J = 6.9 Hz, 2H), 7.47
3
3
8-methylquinolin-2-one (28b): 3,3-diethoxy-N-(o-tolyl)propanamide 27b
(16.3 g, 64.9 mmol) was added to conc. H2SO4 (100 mL) and stirred for
3 h at room temperature. Then the solution was carefully poured on
crushed ice (500 mL) and the resulted solid was filtered off. The solid was
washed with water until the filtrate was neutral. The aqueous layer was
extracted with dichloromethane (2 x 100 mL) and the combined organic
layers were dried with MgSO4 and evaporated. The combined beige solid
(8.1 g, 78 %) was dried over CaCl2. 1H-NMR (400 MHz, CDCl3): δ (ppm) =
9.56 (s, 1H), 7.77 (d, 3J = 9.5 Hz, 1H) 7.42 (d, 3J = 7.8 Hz, 1H), 7.35 (d, 3J
= 7.3 Hz, 1H) 7.13 (t, 3J = 7.6 Hz, 1H), 6.67 (d, 3J = 9.5 Hz, 1H), 2.49 (s,
3H). 13C-NMR (100 MHz, CDCl3): δ (ppm) = 163.3, 141.5, 136.9, 132.0,
126.3, 123.0, 122.4, 121.5, 119.8, 16.8.
3
3
(d, J = 8.4 Hz, 2H), 7.38 (t, J = 7.6 Hz, 2H), 4.76 (s, 2H), 2.85 (s, 6H).
13C-NMR (100 MHz, CDCl3): δ (ppm) = 158.8, 147.1, 137.1, 136.5, 129.5,
126.8, 125.8, 125.6, 121.9, 49.5, 18.1. HRMS (EI): calcd. for C21H18N2 [M.+]
298.1465; found: 298.1448. Anal. calcd. for C21H18N2: C, 84.53; H, 6.08;
N, 9.39; found: C, 83.77; H, 6.06; N, 9.26. The compound is quickly
oxidized by air, resulting in a change of colour and an unsatisfactory
elemental analysis.
Bis-(8-methyl-1,2,3,4-tetrahydroquinolin-2-yl)methane (32): To
a
2-chloro-8-methylquinoline (21b): A solution of 8-methylquinolin-2-one
28b (8.1 g, 50.9 mmol) and phosphoryl chloride (42 mL) was heated to
reflux for 30 min. After cooling to room temperature the solution was
poured into ice water with HCl (500 mL, pH = 1) and neutralized until the
product precipitated from the solution. The aqueous suspension was
extracted with dichloromethane (4 x 50 mL) and the separated organic
layer was dried with MgSO4. After the solution was passed through a plug
of celite in a glas frit (por. 3) the solvent was evaporated. The product
(8.5 g, 94 %) was obtained as a beige solid. 1H-NMR (400 MHz, CDCl3): δ
(ppm) = 8.00 (d, J = 8.5 Hz, 1H), 7.94 (d, J = 8.1 Hz, 1H), 7.71 (t, J =
7.0 Hz, 1H), 7.55 (t, 1H), 7.22 (d, 3J = 8.5 Hz, 1H), 2.66 (s, 3H). 13C-NMR
(100 MHz, CDCl3): δ (ppm) = 150.6, 147.8,, 147.7, 130.4, 129.2, 127.0,
126.8, 123.9, 122.6, 18.7. HRMS (EI): calcd. for C10H8ClN+ [M+] 177.0340;
found: 177.0341. Anal. calcd. for C10H8ClN: C, 67.62; H, 4.54; N, 7.89;
found: C, 67.85; H, 4.53; N, 7.70.
solution of bis(8-methylquinolin-2-yl)methane (23) (250 mg, 0.8 mmol) in
11.25 mL glacial acetic acid/methanol (8:1, v/v), NaBH3CN (300 mg,
4.8 mmol) was added and stirred at 15 °C. Additional NaBH3CN (300 mg,
4.8 mmol) was added in three steps over 3 h and stirred for a further hour.
The mixture was diluted with aqueous NaOH (10 %) and extracted with
dichloromethane (50 mL). The combined organic phases were dried with
MgSO4, filtered and evaporated. The product (157 mg, 60 %) was
obtained as a slight yellow solid after purification by flash chromatography
(pentane:TBME, 10:1 (v/v)). 1H-NMR (400 MHz, CDCl3): δ (ppm) = 6.94 –
3
3
3
3
6.91 (m, 4H), 6.73 (t, J = 7.4 Hz, 2H), 4.14 (s, 1H), 3.73 (s, 1H), 3.67 –
4
3.56 (m, 2H), 3.01 – 2.80 (m, 4H), 2.12 (d, J = 3.9 Hz, 6H), 2.10 – 1.97
(m, 2H), 1.90 – 1.69 (m, 4H). 13C-NMR (100 MHz, CDCl3) δ (ppm) = 142.6
& 142.2, 128.0 & 127.9, 127.4 & 127.3, 121.6 & 121.5, 120.9 & 120.8,
117.0 116.9, 49.6 & 49.3, 44.0 & 42.6, 28.5 & 28.5, 27.0 & 26.4, 17.4 &
+
17.3. HRMS (ESI+): calcd. for C21H27N2 [M + H]+ 307.2169; found:
307.2175. Anal. calcd. for C21H26N2: C, 82.31; H, 8.55; N, 9.14; found: C,
82.22; H, 8.59; N, 9.46.
2-iodo-8-methylquinoline (31): NaI (4.5 g, 30 mmol, ca. 3 – 4 eq.) was
suspended in
a solution of 2-chloro-8-methylquinoline 21b (1.5 g,
8.4 mmol) in dioxane. After the addition of some drops of conc. HI solution
the mixture was heated to reflux under stirring for 8 – 10 h. After the
reaction was completed the solid was filtered off and washed with a little
dioxane. The solid was dissolved in an aqueous NaOH solution (20 mL)
and extracted with dichloromethane (2 x 20 mL). The combined organic
layers were dried with MgSO4, filtered and evaporated. The product was
obtained as a yellow solid (1.2 g, 52 %). 1H-NMR (400 MHz, CDCl3): δ
(ppm) = 7.70 (s, 2H), 7.60 (d, 3J = 8.1 Hz, 1H), 7.55 (d, 3J = 7.0 Hz, 1H),
7.46 – 7.42 (m, 1H), 2.76 (s, 3H). 13C-NMR (100 MHz, CDCl3): δ (ppm) =
148.8, 137.3, 137.0, 131.7, 130.2, 127.2, 126.9, 125.7, 118.0, 17.8. HRMS
(EI): calcd. for C10H8IN+ [M+] 268.9696; found 268.9693. Anal. calcd. for
C10H8IN : C, 44.64; H, 3.00; N, 5.21; found: C, 44.47; H, 3.02; N, 4.92.
Acknowledgements
We are very grateful for the help of Dr. Jonathan Becker (Justus-
Liebig-Universität Giessen) for the preparation of the crystal data.
Keywords: N ligands • Chelates • Nitrogen Heterocycles •
Homogenous Catalysis • Quinolines
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[2]
[3]
[4]
2,8-dimethylquinoline (22): A solution of o-toluidine (38 g, 0.355 mol),
ethyl vinyl ether (77.5 g, 1.07 mol, 3 eq.), PdCl2 (3 g, 0.017 mol) and Pd/C
(20 mg) in acetonitrile (375 mL) was heated to reflux for 8 h. After cooling
to room temperature the solvent was evaporated. The product (32.2 g,
58 %) was obtained as a colourless liquid after distillation (60 °C,
0.01 mbar). 1H-NMR (400 MHz, CDCl3): δ (ppm) = 7.98 (d, 3J = 8.3 Hz,
1H), 7.59 (d, 3J = 8.1 Hz, 1H), 7.51 (d, 3J = 7.0 Hz, 1H), 7.35 (t, 1H), 7.25
(d, 3J = 8.2 Hz, 1H), 2.80 (s, 3H), 2.75 (s, 3H). 13C-NMR (100 MHz, CDCl3):
[5]
[6]
[7]
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