November 2011 An Efficient and Convenient Approach for the Synthesis of Novel 2-Hydroxy-
12-aryl-8,9,10,12-tetrahydrobenzo[a]xanthene-11-ones Using pTSA in Ethanol and Ionic Liquid
1391
values are recorded on d scale and the coupling constants (J)
are in Hertz. Mass spectra were recorded on JEOL-AccuTOF
JMS–T100 mass spectrometer having a DART source.
7.75 (m, 2H, ArAH), 7.67 (d, J ¼ 7.8 Hz, 1H, ArAH), 7.54 (t,
J ¼ 7.8 Hz, 1H, ArAH), 7.25–7.16 (m, 2H, ArAH), 6.98–6.95
(m, 1H, ArAH) 5.50 (s, 1H, CH), 2.72 and 2.62 (AB system, J
¼ 17.7 Hz, 2H, CHaCHbC(CH3)2), 2.37 (d, J ¼ 16.2 Hz, 1H),
2.16 (d, J ¼ 16.2 Hz, 1H), 1.05 (s, 3H, CH3), 0.84 (s, 3H,
CH3). 13C NMR (300 MHz, DMSO-d6): dC 195.99, 164.44,
156.67, 147.76, 147.53, 146.62, 134.66, 132.22, 130.37,
129.75, 129.43, 125.49, 122.52, 121.47, 117.30, 113.95,
113.51, 112.29, 104.90, 49.94, 34.20, 31.90, 28.66, 26.15. IR
(KBr) (mmax, cmꢁ1): 3182, 2962, 1625, 1594, 1526, 1382,
1350, 1224. MS (ESI): m/z ¼ 416 (M þ H)þ.
General procedure for the synthesis of 2-hydroxy-12-
aryl-8,9,10,12-tetrahydrobenzo[a]xanthen-11-one derivatives
(1a–w). Method A A mixture of aldehyde (1.0 mmol), 2,7-
dihydroxynaphthalene (1.0 mmol), 5,5-dimethyl-1,3-cyclohexa-
nedione/1,3-cyclohexanedione (1.2 mmol), pTSA (2 mol% or
0.02 mmol) and 10 mL of ethanol was placed in 50 mL
round-bottomed flask and stirred under reflux for an appropri-
ate time as mentioned in Table 2. After completion of the
reaction as monitored by TLC (petroleum ether : ethyl ace-
tate), the reaction mixture was allowed to cool to room tem-
perature. The precipitate formed was collected by filtration at
pump, washed with ethanol, and dried to obtain pure xanthen-
11-one derivatives.
Method B A mixture of aldehyde (1.0 mmol), 2,7-dihydrox-
ynaphthalene (1.0 mmol), 5,5-dimethyl-1,3-cyclohexanedione/
1,3-cyclohexanedione (1.2 mmol), and pTSA (2 mol% or 0.02
mmol) were taken in a 25 mL round-bottomed flask containing
0.5 mL of [bmim]BF4. The mixture was stirred at 50ꢀC for an
appropriate time as mentioned in Table 2. After completion of
the reaction as monitored by TLC, the mixture was allowed to
cool to room temperature and quenched with water (ꢂ5 mL).
The precipitate formed was collected by filtration at pump,
washed with ethanol, and dried to obtain pure xanthen-11-one
derivatives. The filtrate was concentrated under reduced pres-
sure and dried at 100ꢀC to recover the ionic liquid for subse-
quent use. Marginal loss in the yield of the products were
observed in first three runs (94, 90, and 85%), whereas in
fourth and fifth runs the yields were quite low.
12-(3-Bromophenyl)-2-hydroxy-9,9-dimethyl-8,9,10,12-tetra-
hydrobenzo[a]xanthen-11-one (1i) White solid; m.p. >300ꢀC
(decom.) 1H NMR (300 MHz, DMSO-d6): dH 9.93 (s, 1H,
OH), 7.80 (t, J ¼ 7.8 Hz, 2H, ArAH), 7.42 (s, 1H, ArAH),
7.30–7.13 (m, 5H, ArAH), 7.00–6.96 (m, 1H, ArAH), 5.34 (s,
1H, CH), 2.70 and 2.61 (AB system, J ¼ 17.4 Hz, 2H,
CHaCHbC(CH3)2), 2.36 (d, J ¼ 16.2 Hz, 1H), 2.16 (d, J ¼
16.2 Hz, 1H), 1.05 (s, 3H, CH3), 0.87 (s, 3H, CH3). 13C NMR
(300 MHz, DMSO-d6): dC 195.93, 164.24, 156.57, 147.68,
147.18, 132.31, 130.70, 130.38, 130.31, 129.19, 129.13,
127.09, 125.46, 121.36, 117.24, 114.52, 113.50,112.68, 104.95,
50.00, 33.96, 31.90, 28.72, 26.12. IR (KBr) (mmax, cmꢁ1):
3157, 2957, 1624, 1593, 1384, 1227, 1170. MS (ESI): m/z ¼
449 (M þ H)þ.
2-Hydroxy-9,9-dimethyl-12-(1-naphthyl)-8,9,10,12-tetrahydro-
benzo[a]xanthen-11-one (1k) White solid; m.p. >300ꢀC
(decom.), 1H NMR (300 MHz, DMSO-d6): dH 9.66 (s, 1H,
OH), 9.00 (brs, 1H, ArAH), 7.85 (d, J ¼ 8.1 Hz, 1H, ArAH),
7.74–7.63 (m, 4H, ArAH), 7.54 (t, J ¼ 7.5 Hz ,1H, ArAH),
7.31–7.21 (m, 3H, ArAH),7.06 (s, 1H, ArAH), 6.94 (d, J ¼
8.7 Hz, 1H, ArAH), 6.11 (s, 1H, CH), 2.70 and 2.59 (AB sys-
tem, J ¼ 17.4 Hz, 2H, CHaCHbC(CH3)2), 2.29 (d, J ¼ 16.2
Hz, 1H), 2.03 (d, J ¼ 16.2 Hz, 1H), 1.01 (s, 3H, CH3), 0.77
(s, 3H, CH3). 13C NMR (300 MHz, DMSO-d6): dC 196.08,
163.72, 156.20, 147.72, 142.41, 133.08, 132.94, 130.34,
130.08, 128.67, 128.28, 127.33, 126.93, 125.99, 125.50,
124.74, 117.17, 117.01, 114.32, 113.70, 105.70, 50.12, 34.47,
31.67, 28.80, 26.08. IR (KBr) (mmax, cmꢁ1): 3152, 2956, 1620,
1589, 1366, 1217, 1170. MS (ESI): m/z ¼ 421 (M þ H)þ.
2-Hydroxy-12-phenyl-8,9,10,12-tetrahydrobenzo[a]xanthen-
11-one (1o) White solid; m.p. >300ꢀC (decom.), 1H NMR
(300 MHz, DMSO-d6): dH 9.86 (s, 1H, OH), 7.76–7.72 (m,
2H, ArAH), 7.25–7.16 (m, 6H, ArAH), 7.08–7.04 (m, 1H,
ArAH), 6.97(d, J ¼ 9 Hz, 1H, ArAH), 5.37 (s, 1H, CH),
2.71–2.69 (m, 2H, CH2), 2.41–2.25 (m, 2H, CH2), 1.99–1.94
(m, 1H), 1.83–1.79 (m, 1H). 13C NMR (300 MHz, DMSO-d6):
dC 196.14, 165.76, 156.38, 147.70, 144.97, 132.46, 130.18,
128.70, 128.15, 128.07, 126.13, 125.45, 117.10, 115.45,
114.57, 113.48, 105.13, 36.40, 34.06, 26.90, 19.91. IR (KBr)
(mmax, cmꢁ1): 3200, 2966, 1625, 1593, 1382, 1230, 1194. MS
(ESI): m/z ¼ 343 (M þ H)þ.
Representative analytical data.
12-(4-Chlorophenyl)-2-
hydroxy-9,9-dimethyl-8,9,10,12
tetrahydrobenzo[a]xanthen-
11-one (1a) White solid; m.p. >300ꢀC (decom.), 1H NMR
(300 MHz, CDCl3): dH 9.29 (s, 1H, OH), 7.67–7.62 (m, 2H,
ArAH), 7.31–7.24 (m, 3H, ArAH), 7.14–7.09 (m, 3H, ArAH),
7.02–6.99 (m, 1H, ArAH), 5.50 (s, 1H, CH), 2.57 (s, 2H,
CH2) 2.33 (d, J ¼ 16.2 Hz, 1H), 2.24 (d, J ¼ 16.2 Hz, 1H),
1.12 (s, 3H, CH3), 0.95 (s, 3H, CH3). 13C NMR (300 MHz,
DMSO-d6): dC 199.4, 166.18, 156.30, 147.96, 142.95, 132.87,
132.04, 130.39, 129.87, 129.04, 128.42, 126.49, 117.39,
115.45, 113.87, 105.86, 50.40, 34.45, 32.51, 29.32, 27.05. IR
(KBr) (mmax, cmꢁ1): 3194, 2929, 1631, 1594, 1381, 1235. MS
(ESI): m/z ¼ 405(M þ H)þ.
2-Hydroxy-9,9-dimethyl-12-phenyl-8,9,10,12-tetrahydroben-
zo[a]xanthen-11-one (1b) White solid; m.p. >300ꢀC (decom.),
1H NMR (300 MHz, DMSO-d6): dH 9.87 (s, 1H, OH), 7.77–
7.72 (m, 2H, ArAH), 7.26–7.17 (m, 6H, ArAH), 7.09–7.04
(m, 1H, ArAH), 6.98–6.94 (m, 1H, ArAH), 5.34 (s, 1H, CH),
2.69 and 2.58 (AB system,
J
¼
17.4 Hz, 2H,
CHaCHbC(CH3)2), 2.35 (d, J ¼ 16.2 Hz, 1H), 2.13 (d, J ¼
16.2 Hz, 1H), 1.05 (s, 3H, CH3), 0.86 (s, 3H, CH3). 13C NMR
(300 MHz, DMSO-d6): dC 195.87, 163.88, 156.39, 147.63,
144.65, 132.46, 130.19, 128.72, 128.07, 128.04, 126.14,
125.45, 117.10, 115.44, 113.52, 113.28, 105.13, 50.06, 34.12,
31.85, 28.81, 26.14. IR (KBr) (mmax, cmꢁ1): 3182, 2959, 1630,
1596, 1379, 1227, 1182. MS (ESI): m/z ¼ 371 (M þ H)þ.
2-Hydroxy-9,9-dimethyl-12-(3-nitrophenyl)-8,9,10,12-tetra-
hydrobenzo[a]xanthen-11-one (1h) White solid; m.p. >300ꢀC
(decom.), 1H NMR (300 MHz, DMSO-d6): dH 9.93 (s, 1H,
OH), 8.11 (s, 1H, ArAH), 7.99–7.96 (m, 1H, ArAH), 7.82–
12-(4-Bromophenyl)-2-hydroxy-8,9,10,12-tetrahydrobenzo[a]x-
anthen-11-one (1s) White solid; m.p. >300ꢀC (decom.), 1H
NMR (300 MHz, DMSO-d6): dH 9.89 (s, 1H, OH), 7.78–7.73
(m, 2H, ArAH), 7.41 (d, J ¼ 8.4 Hz, 2H, ArAH), 7.21–7.13
(m, 4H, ArAH), 6.99–6.95 (m, 1H, ArAH), 5.35 (s, 1H, CH),
2.73–2.69 (m, 2H, CH2), 2.37–2.26 (m, 2H, CH2), 1.99–1.93
(m, 1H), 1.86–1.83 (m, 1H). 13C NMR (300 MHz, DMSO-d6):
dC 196.19, 165.90, 156.49, 147.65, 144.27, 132.33, 131.06,
130.32, 130.28, 128.99, 125.44, 119.28, 117.16, 114.70,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet