10.1002/ejoc.201901599
European Journal of Organic Chemistry
FULL PAPER
7,10-dimethyl-1-tosyl-1,2,3,4-tetrahydrobenzo[g]quinoline
(p-9e):
(CH3), 21.7 (CH3), 16.5 (CH3). HRMS (ESI) m/z: calcd. for C22H23NO2SNa+
Separated from regioisomer o-9e by HPLC (9:1 MeCN/H2O, 2.5 ml/min).
White solid, 42% yield (66% total yield of two isomers), mp 188-190 °C. Rf
0.45 (8:2 PE/Et2O). 1H NMR (600 MHz) δ (ppm): 7.97 (d, 1H, J = 8.6 Hz),
7.50 (s, 1H), 7.44 (d, 2H, J = 8.3 Hz), 7.35 (dd, 1H, J = 8.6 Hz, 1.4 Hz),
7.22 (s, 1H), 7.19 (d, 2H, J = 7.9 Hz), 4.11 (td, 1H, J = 13.8 Hz, 8.6 Hz),
3.53 (ddd, 1H, J = 13.1 Hz, 8.3 Hz, 4.1 Hz), 2.80 (s, 3H), 2.51 (s, 3H), 2.41
(s, 3H), 2.36-2.32 (m, 1H), 2.05-1.98 (m, 1H), 1.54-1.47 (m, 1H), 1.42 (td,
12.9 Hz, 4.8 Hz). 13C NMR (150 MHz) δ (ppm): 143.6 (Cq), 137.0 (Cq),
136.1 (Cq), 135.8 (Cq), 134.7 (Cq), 132.7 (Cq), 132.5 (Cq), 131.1 (Cq),
129.7 (CH), 127.8 (CH), 127.7 (CH), 126.7 (CH), 125.3 (CH), 123.4 (CH),
45.9 (CH2), 26.7 (CH2), 24.0 (CH2), 21.7 (CH3), 21.7 (CH3), 16.4 (CH3).
HRMS (ESI) m/z: calcd. for C22H23NO2SNa+ 388.1347, found 388.1345.
388.1347; found 388.1349.
Synthesis
of
8-methoxy-10-methyl-1,2,3,4-
tetrahydrobenzo[g]quinoline (10a): The N-tosyl deprotection was
performed according to a literature procedure.[26a] A solution of 9a (1.0 eq,
0.2 mmol) in anhydrous DME (0.1 M) was cooled down to -78 °C. A 1.0 M
solution of Na and naphthalene (6.0 eq) in anhydrous DME was prepared.
The colour of sodium naphthalenide is dark green. The solution of sodium
naphthalenide was slowly added to the solution of 9a at -78 °C until the
dark green colour was persistent. The mixture was stirred at -78 °C for 30
min, then it was allowed to warm to room temperature, H2O was added
and the mixture was extracted three times with EtOAc; the combined
organic layers were dried over anhydrous Na2SO4, filtered and the solvent
was removed under vacuum. The crude product was purified by flash
column chromatography to afford pure 10a as an off-white solid. 75% yield,
9,10-dimethyl-1-tosyl-1,2,3,4-tetrahydrobenzo[g]quinoline
(o-9e):
Separated from regioisomer p-9e by HPLC (9:1 MeCN/H2O, 2.5 ml/min).
White solid, 24% yield (66% total yield of two isomers). Rf 0.45 (8:2
PE/Et2O). 1H NMR (600 MHz) δ (ppm): 7.55 (d, 1H, J = 8.3 Hz), 7.47 (d,
2H, J = 8.3 Hz), 7.33-7.29 (m, 1H), 7.28-7.26 (m, 2H), 7.20 (d, 2H, J = 7.6
Hz), 4.16-4.10 (m, 1H), 3.48 (ddd, 1H, J = 13.1 Hz, 8.3 Hz, 4.8 Hz), 2.97
(s, 3H) superimposed to 2.97 (s, 3H), 2.41 (s, 3H), 2.36 (ddd, 1H, J = 14.5
Hz, 5.2 Hz, 2.8 Hz), 1.54-1.48 (m, 1H), 1.43 (td, 1H, J = 13.2 Hz, 6.0 Hz).
13C NMR (150 MHz) δ (ppm): 143.6 (Cq), 137.1 (Cq), 136.7 (Cq), 136.7
(Cq), 135.3 (Cq), 135.0 (Cq), 140.0 (Cq), 133.7 (Cq), 129.7 (CH), 129.6
(CH), 127.7 (CH), 126.8 (CH), 125.8 (CH), 125.1 (CH), 45.7 (CH2), 26.6
(CH2), 26.2 (CH3), 24.0 (CH2), 21,9 (CH3), 21.8 (CH3). HRMS (ESI) m/z:
calcd. for C22H23NO2SNa+ 388.1347, found 388.1343.
1
mp 114-116 °C (hexane). Rf 0.40 (9:1 PE/EtOAc). H NMR (600 MHz) δ
(ppm): 7.52 (d, 1H, J = 8.8 Hz), 7.28 (s, 1H), 7.08 (d, 1H, J = 2.1 Hz), 6.85
(dd, 1H, J = 8.8, 2.2 Hz), 3.92 (s, 3H), 3.49-3.47 (m, 2H), 2.96 (d, 2H, J =
6.4 Hz), 2.31 (s, 3H), 1.99 (quin, 2H, J = 6.2 Hz). 13C NMR (150 MHz) δ
(ppm): 157.6 (Cq), 141.2 (Cq), 133.5 (Cq), 129.5 (CH), 125.8 (CH), 122.8
(Cq), 122.0 (Cq), 113.4 (CH), 109.9 (Cq), 101.4 (CH), 55.3 (CH2), 42.8
(CH2), 28.3 (CH2), 22.3 (CH2), 11.5 (CH3). HRMS m/z: calcd. for 250.1208,
found 250.1211.
Acknowledgments
7,9,10-trimethyl-1-tosyl-1,2,3,4-tetrahydrobenzo[g]quinoline
(9f):
White solid, 58% yield, mp 202-203 °C (MeCN). Rf 0.28 (9:1 PE/Et2O). 1H
NMR (600 MHz) δ (ppm): 7.46 (d, 2H, J = 8.2 Hz), 7.32 (s, 1H), 7.18 (d,
2H, J = 8.1 Hz) superimposed to 7.17 (s, 1H), 7.12 (s, 1H), 4.12 (ddd, 1H,
J = 13.8 Hz, 8.8 Hz, 7.8 Hz), 3.50-3.45 (m, 1H), 2.95 (s, 3H), 2.93 (s, 3H),
2.43 (s, 3H), 2.40 (s, 3H), 2.33 (ddd, 1H, J = 14.5 Hz, 5.3 Hz, 2.8 Hz), 2.04-
1.98 (m, 1H), 1.54-1.47 (m, 1H), 1.42-1.36 (m, 1H). 13C NMR (150 MHz) δ
(ppm): 143.5 (Cq), 137.1 (Cq), 136.5 (Cq), 136.4 (Cq), 135.4 (Cq), 135.2
(Cq), 134.3 (Cq), 134.2 (Cq), 131.9 (CH), 131.8 (Cq), 129.6 (CH), 127.7
(CH), 125.8 (CH), 124.5 (CH), 45.8 (CH2), 26.6 (CH2), 26.1 (CH3), 24.0
(CH2), 21.7 (CH3), 21.2 (CH3). HRMS (ESI) m/z: calcd. for C23H25NO2SNa+
402.1504; found 407.1500.
We would like to thank prof. Christopher Mc Erlean for fruitful
discussions during his stay at the University of Turin as visiting
professor. We would also like to thank dr. Emanuele Priola for X-
Ray analysis and prof. Alessandro Barge for ESI-MS analysis. We
thank MIUR (Italian Ministery of University and Research) and
CRT (Cassa di Risparmio di Torino) for funding.
Keywords: gold catalysis • hydroarylation • nitrogen heterocycles
• benzoquinolines • enynes
7,8,9-trimethoxy-10-methyl-1-tosyl-1,2,3,4-
tetrahydrobenzo[g]quinoline (9g): White solid, 63% yield, mp 166-
167 °C (i-Pr2O). Rf 0.36 (8:2 PE/EtOAc). 1H NMR (600 MHz) δ (ppm): 7.51
(d, 2H, J = 7.9 Hz), 7.21 (d, 2H, J = 7.9 Hz), 7.14 (s, 1H), 6.83 (s, 1H),
4.14-4.08 (m, 1H), 3.96 (s, 3H), 3.96 (s, 6H), 3.49-3.44 (m, 1H), 2.92 (s,
3H), 2.41 (s, 3H), 2.34-2.30 (m, 1H), 2.06-1.99 (m, 1H), 1.52-1.47 (m, 2H).
13C NMR (150 MHz) δ (ppm): 152.9 (Cq), 151.5 (Cq), 143.5 (Cq), 142.4
(Cq), 137.2 (Cq), 135.8 (Cq), 134.8 (Cq), 133.1 (Cq), 130.8 (Cq), 129.6
(CH), 127.7 (CH), 123.7 (Cq), 123.0 (CH), 102.8 (CH), 61.6 (CH3), 61.2
(CH3), 55.9 (CH3), 45.7 (CH2), 26.6 (CH2), 24.0 (CH2), 24.0 (CH2), 21.7
(CH3), 19.2 (CH3). HRMS (ESI) m/z: calcd. for C24H27NO5SNa+ 464.1508;
found 464.1505.
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[2]
[3]
8,10-dimethyl-1-tosyl-1,2,3,4-tetrahydrobenzo[g]quinoline (9h): White
solid, 57% yield, mp 178-179 °C (hexane). Rf 0.36 (8:2 PE/Et2O). 1H NMR
(600 MHz) δ (ppm): 7.85 (s, 1H), 7.63 (d, 1H, J = 8.3 Hz), 7.45 (d, 2H, J =
8.3 Hz), 7.32 (dd, 1H, J = 8.3, 1.4 Hz), 7.27 (s, 1H), 7.19 (d, 2H, J = 8.3
Hz), 4.14-4.08 (m, 1H), 3.53 (ddd, 1H, J = 13.1, 7.9, 4.1 Hz), 2.80 (s, 3H),
2.56 (s, 3H), 2.41 (s, 3H), 2.37-2.33 (m, 1H), 2.05-1.98 (m, 1H), 1.55-1.48
(m, 1H), 1.44 (td, 1H, J = 13.1, 5.5 Hz). 13C NMR (150 MHz) δ (ppm): 143.6
(Cq), 137.1 (Cq), 135.2 (Cq), 135.0 (Cq), 134.1 (Cq), 135.6 (Cq), 133.0
(Cq), 130.5 (Cq), 129.7 (CH), 128.3 (CH), 128.3 (CH), 127.7 (CH), 127.5
(CH), 124.6 (CH), 123.8 (CH), 45.9 (CH2), 26.6 (CH2), 24.1 (CH2), 22.2
[4]
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