DOI:
10.1039/C4RA12298D
(Paper)
RSC Adv., 2015,
5, 11745-11752
Secondary amine based ionic liquid: an efficient catalyst for solvent free one pot synthesis of xanthenes and benzoxanthenes†
Received
13th October 2014
, Accepted 9th January 2015
First published on 9th January 2015
Abstract
Ionic liquids (IL) prepared from dialkylamines and concentrated sulphuric acid were used in an operationally simple, cost effective, efficient and environmentally benign synthesis of xanthenes and benzoxanthenes. Three ILs were screened for their efficiency as promoter of the synthesis. Results indicate di-n-propylammoniumhydrogensulphate to be the most efficient IL. Product recovery is simple and the IL could be recovered for reuse.
Introduction
The use of ILs as environmentally benign reaction solvents for synthesis and catalysis has been recognized. Their environmentally favourable qualities such as nonvolatility, high thermal stability, excellent solubility and extended liquid range have contributed to their versatility and increasing applicability.1 Recently, ILs with different morphology and with improved quality like ionic liquid marbles,2 stable room temperature ionic liquids,3 ionic liquid crystals,4 poly(ionic liquid)s,5 ionic liquids with metal chelate counter anion,6 and biodegradable ionic liquids7 were synthesized and have found application in different fields including the transformation of renewable biomass into functional carbon materials by the ionothermal carbonization process.8
Xanthene and benzoxanthene are important heterocycles with a variety of applications in the field of pharmaceutical chemistry.9 The xanthene moiety being a source of brilliant fluorescent dye is widely used in chemical biology as tracers for proteins, DNAs, sugars with high sensitivity and selectivity.10 Their application in laser technology is well documented.11 Notable pharmaceutical activities of xanthene derivatives includes antibacterial,12 analgesic,13 antiviral,14 anti-inflammatory,15 antimalarial and inhibitory action towards trypanothione reductase enzymes and chloroquine potentiating agent,16 besides others. The versatility of xanthenes derivatives have attracted attention of synthetic chemists towards their preparation and scaffold manipulation using improved procedure. Condensation of dimedone, aldehyde and 2-naphthol is the usual procedure for library synthesis of xanthene, benzoxanthene and their structural variants. Classical methods of the synthesis include reaction of 2-naphthol with aldehydes or acetals under acidic conditions17 and the reaction of aryloxymagnesium halides with triethyl orthoformate.18 Zhao et al. synthesized xanthones, thioxanthones by the reaction of silylaryl triflates, CsF and ortho-heteroatom substituted benzoates by the intermolecular nucleophilic coupling followed by intramolecular electrophilic cyclization.19 Other methods include palladium-catalyzed cyclization of polycyclic aryltriflate esters,20 annulation reaction of benzyne with salicylaldehyde,21 coupling reaction of arynes with aldehydes via ortho-quinone methides22 and reaction of 2-tetralone and 2-hydroxy aromatic aldehydes under acidic conditions.23 The target molecules have also been synthesized by a one pot multicomponent reaction using HY zeolite.24 Li et al. used proline triflate as catalyst for the synthesis under reflux condition in water.25 Other reported catalysts that promoted the reaction are strontium triflate,26 indium(III) chloride and P2O5,27 silica sulfuric acid,28 quasi homogeneous magnetic silica-coated Fe3O4 nanoparticle supported on 3-sulfobutyl-1-(3-propyltriethoxysilane)imidazolium29 besides others. The synthesis of (9-aryl/alkyl-octahydroxanthene-1,8-diones) have been reported by Shakibaei et al. using Dowex-50W ion exchange resin as reusable catalyst.30 Kantevari et al. compared the catalytic efficiency of HClO4–SiO2 and polyphosphoric acid–SiO2 as catalyst in a variety of solvents and observed that in acetonitrile and under solvent free conditions polyphosphoric acid–SiO2 gave selectively 1,8-dioxooctahydroxanthene whereas HClO4–SiO2 gave 2,2′-arylmethylene bis (3-hydroxy-5,5-dimethyl-2-cyclohexene-1-one) as major products.31 Other catalysts used for promoting the condensation includes methanesulfonic acid,32 p-dodecylbenzenesulfonic acid (DBSA),33 NaHSO4–SiO2 (ref. 34) tetrabutylammoniumhydrogensulphate (TBAHS),35 trimethylsilyl chloride (TMSCL)36 etc. The application of ILs as promoter for the reaction was demonstrated by Kidwai using imidazolium based IL [bmim]PF6 as solvent,37 Khaligh applied poly(4-vinylpyridinium)hydrogensulphate as catalyst for the synthesis of three xanthene derivatives namely 14-aryl-14H-dibenzo[a,j]xanthene-8,13-diones, dibenzo[b,i]xanthenetetraones and aryl-14H-dibenzo[a,j]xanthenes by using 2-naphthol, 2-hydroxynaphthalene-1,4-dione and aryl halide as reactant.38
Results and discussions
Although some acid catalysts were found to be efficient for the synthesis of xanthenes derivatives most procedures suffer from one or more disadvantages notably prolonged reaction time, tedious work up procedures, use of VOCs and hazardous reaction conditions. Chemoselectivity can be a problem in the presence of acid sensitive groups. A few instances of the use of ILs as solvents as well as promoter in the synthesis have been reported, but high cost of imidazole, thiazole and pyridine based IL and concomitant use of costly catalyst for the synthesis have been the essential drawbacks. To overcome these disadvantages, herein is reported simple yet efficient procedures for the synthesis of the xanthenes derivatives particularly 9,9-dimethyl-12-aryl-8,9,10,12-tetrahydro-benzo[a]xanthenes-11-one,3,3,6,6-tetramethyl-9-aryl-1,2,3,4,5,6,7,8-octahydro-xanthene-1,8-dione and 14-aryl-14[H]-dihydro-dibenzo[a,j]xanthenes using environmental benign, cheap and easily preparable IL derived from a dialkylamines which perform the role of a catalyst. The VOC free synthetic protocol reported here offers additional advantage of simple work up and easy product recovery. The IL could be easily recovered and recycled. Three ILs namely [Et2NH2][HSO4] (diethylammonimhydrogensulphate), [(n-propyl)2NH2][HSO4] (di-n-propylammoniumhydrogensulphate) and [(iso-propyl)2NH2][HSO4] (di-iso-propylammoniumhydrogen sulphate) were synthesized from the appropriate dialkylamine and concentrated sulphuric acid. The essentiality of acidic IL catalyst to promote the reaction is established by the observation that in the absence of IL the reaction did not proceed. Further the three ILs were screened for their efficiency in a representative reaction of 4-nitrobenzaldehyde and dimedone for the formation of 2b (Table 1) and on the basis of reaction time and yield it was observed that [Et2NH2][HSO4] and [(n-propyl)2NH2][HSO4] were more efficient than [(iso-propyl)2NH2][HSO4]. However thermal stability of [(n-propyl)2NH2][HSO4] compared to [Et2NH2][HSO4] at the optimum temperature encouraged us to use [(n-propyl)2NH2][HSO4] as the IL of choice in all our reactions. Consequent to this observation, this IL was used in carrying out the syntheses reported here (Table 2).
Table 1 Screening for efficiency of the ionic liquids on the synthesis of 2b (50 mol% IL was used)
Entry |
Ionic liquid |
Time (min) |
Yielda (%) |
Isolated product. |
1 |
[Et2NH2][HSO4] |
10 |
83 |
2 |
[(n-Propyl)2NH2][HSO4] |
10 |
85 |
3 |
[(Iso-propyl)2NH2][HSO4] |
10 |
72 |
4 |
None |
120 |
0 |
Table 2 Synthesis of xanthene derivatives catalysed by [(n-propyl)2NH2][HSO4] ionic liquid
Entry |
R |
Product |
Time (min) |
Yielda (%) |
Isolated product. 0.2 mL of aldehyde used. New compound. Catalyst reused: 1st run. Catalyst reused: 2nd run. Catalyst reused: 3rd run. |
1 |
4-ClC6H4 |
1a |
15 |
80 |
2 |
4-NO2C6H4 |
1b |
15 |
79 |
3 |
4-CH3C6H4 |
1c |
15 |
82 |
4 |
4-OCH3C6H4 |
1d |
15 |
82 |
5 |
C6H5 |
1e |
15 |
78 |
6 |
2-Naphthyl |
1f |
15 |
78 |
7 |
2-OCH3C6H4 |
1g |
15 |
82 |
8 |
Iso-CH(CH3)2 |
1h |
20 |
65b |
9 |
4-ClC6H4 |
2a |
10 |
85 |
10 |
4-NO2C6H4 |
2b |
10 |
85 |
11 |
4-OCH3C6H4 |
2c |
10 |
85 |
12 |
4-OHC6H4 |
2d |
10 |
82 |
13 |
4-CH3C6H4 |
2e |
10 |
86 |
14 |
3-ClC6H4 |
2f |
10 |
83 |
15 |
2,6-Cl2C6H3 |
2g |
10 |
82 |
16 |
2,5-(OH)(NO2)C6H3 |
2h |
10 |
83 |
17 |
CH3 |
2i |
20 |
72b |
18 |
C6H5CH2CH2 |
2j |
10 |
87c |
19 |
Iso-CH(CH3)2 |
2k |
20 |
70b |
20 |
4-ClC6H4 |
3a |
30 |
67 |
21 |
4-NO2C6H4 |
3b |
30 |
65 |
22 |
4-CH3C6H4 |
3c |
30 |
69 |
23 |
4-OHC6H4 |
3d |
30 |
69 |
24 |
2-OCH3C6H4 |
3e |
30 |
70 |
25 |
CH3 |
3f |
30 |
69b |
26 |
Iso-CH(CH3)2 |
3g |
25 |
65b |
27 |
2-OCH3C6H4 |
1g |
15 |
82d |
28 |
2-OCH3C6H4 |
1g |
15 |
82e |
29 |
2-OCH3C6H4 |
1g |
15 |
82f |
To determine the optimum amount of the [(n-propyl)2NH2][HSO4] IL necessary for less reaction time and maximum yield, the model reaction of dimedone and p-anisaldehyde for the formation of 2c (Table 2) was selected. The mol% of the IL was changed and the optimum quantity of IL required for maximum yield and shortest reaction time was found to be 50 mol% (Fig. 1).
 |
| Fig. 1 Effect of amount of [(n-propyl)2NH2][HSO4] IL on the synthesis of 2c. | |
In the first instance, the three component reaction of 2-naphthol, dimedone and aldehyde was carried out in di-n-propylammoniumhydrogensulphate to give the 9,9-dimethyl-12-aryl-8,9,10,12-tetrahydrobenzo[a]xanthenes-11-one in high yield (Scheme 1). In a subsequent reaction using only the dimedone and aldehyde as the substrates in the molar ratio 2
:
1 and the product obtained was 3,3,6,6-tetramethyl-9-aryl-1,2,3,4,5,6,7,8-octahydro-xanthene-1,8-dione (Scheme 2) and finally a reaction of 2-naphthol and aldehyde in the molar proportion of 2
:
1 gave the 14-aryl-14[H]-dihydro-dibenzo[a,j]xanthenes (Scheme 3). In comparison to aromatic aldehydes, aliphatic aldehydes are found to be less reactive under this reaction conditions giving reasonably low yields.
 |
| Scheme 1 Synthesis of 9,9-dimethyl-12-aryl-8,9,10,12-tetrahydrobenzo[a]xanthenes-11-one. | |
 |
| Scheme 2 Synthesis of 3,3,6,6-tetramethyl-9-aryl-1,2,3,4,5,6,7,8-octahydro-xanthene-1,8-dione. | |
 |
| Scheme 3 Synthesis of 14-aryl-14[H]-dihydrodibenzo[a,j]xanthenes. | |
Experimental procedure for all the three reactions involve mixing the substrates and IL in the right proportions, grinding to give a oily homogeneous mixture followed by thermal heating at 80 °C in an oil bath for 10–30 minutes in the absence of solvents. The oily homogeneous mixture solidified on completion of the reaction as indicted by TLC. Addition of ethylacetate to the crude product precipitated the insoluble IL which could be recovered in high state of purity by simple filtration and reused for three successive run without any appreciable loss of activity (all these representative steps are shown in Fig. S1 in ESI†). The products were crystallized from ethylacetate extract. The results are summarized in Table 2.
It can be seen from Table 2 that a variety of aldehydes both aromatic as well as aliphatic aldehydes respond similarly and give similar products under identical reaction conditions. However, we observed that with aliphatic aldehydes, the % yield is generally lower than those obtained from aromatic aldehydes and requires higher reaction time. Further, among the aromatic aldehydes, the % yield and the reaction time is not influenced by the nature and electronic effects of the substituents present in the phenyl ring.
All products obtained were characterized by IR, 1H NMR, 13C NMR, mass spectrometry and by comparing the melting points with those reported in literature. Single crystal X-ray analysis of one of the product namely 14-(4-methylphenyl)-14[H]-dihydro-dibenzo[a,j]xanthenes (3c) confirms the structure (Fig. 2) (Table 3).
 |
| Fig. 2 ORTEP diagram of 3c. | |
Table 3 Crystallographic parameter of compound 3c
Chemical formula |
C28H20O |
Formula mass |
372.44 |
Crystal system |
Orthorhombic |
Space group |
Pna2(1) |
T (K) |
296 |
a/Å |
14.015(4) |
b/Å |
17.350(6) |
c/Å |
7.950(2) |
α/degree |
90.00 |
β/degree |
90.00 |
γ/degree |
90.00 |
Unit cell volume/Å3 |
1933.2(10) |
Dcalcd (g cm−3) |
1.280 |
μ (mm−1) |
0.076 |
Z |
4 |
Reflns collected |
9212 |
Unique reflns |
4050 |
Observed reflns |
2410 |
R1 [I > 2σ(I)] |
0.0607 |
wR2 (all) |
0.1219 |
Goodness-of-fit |
1.082 |
Diffractometer |
SMART Bruker Apex-II |
CCDC number |
1025707 |
A comparison of results obtained in this study with some reported procedures is presented in Table 4. Data indicate the superiority of the present procedure over others in terms of yield, time, reaction conditions and ease of product recovery.
Table 4 Comparison of the efficiency of ionic liquid ([(n-propyl)2NH2][HSO4]) with some reported catalyst for the synthesis of xanthenes and benzoxanthenes
Entry |
Catalyst |
Temp. (°C) |
Time |
Yield (%) |
Ref. |
1 |
InCl3/P2O5 |
120 |
25–80 min |
58–88 |
27 |
2 |
[n-WO3–SO3H] |
100 |
75–100 min |
83–94 |
44 |
3 |
AIL@MNP |
90 |
30–65 min |
80–94 |
29 |
4 |
HY zeolite |
80 |
1–24 h |
70–95 |
24 |
5 |
Dowex-50W |
100 |
1.5–5 h |
78–91 |
30 |
6 |
NaHSO4·SiO2 |
Reflux |
6–6.5 h |
90–98 |
45 |
7 |
[Hmim]TFA |
80 |
2.5–4 h |
80–94 |
46 |
8 |
Nano-TiO2 |
100 |
15–90 min |
81–96 |
47 |
9 |
Amberlite IR-120H |
Reflux |
1.5–3 h |
70–94 |
48 |
10 |
ZrTPA |
130 |
1–5 h |
54–98 |
49 |
11 |
P2O5/InCl3 |
80 |
30–75 min |
50–94 |
50 |
12 |
CoPy2Cl2 |
85 |
1.5–8 h |
65–97 |
51 |
13 |
Heteropoly acid |
100 |
1–1.5 h |
81–94 |
52 |
14 |
p-TSA |
125 |
2.5–6 h |
80–96 |
53 |
15 |
I2 |
90 |
2–5 h |
85–95 |
54 |
16 |
[(n-Propyl)2NH2][HSO4] |
80 |
10–30 min |
65–86 |
|
Conclusion
Experiments indicate that a solvent free multicomponent reaction of dimedone, aldehyde and 2-naphthol can be carried out by using the easily prepared IL namely the di-n-propylammoniumhydrogensulphate which performs the role of a catalyst. The nature of the products varied with the variation in the composition of the reaction mixture. The reactions were simple and efficient for both aromatic and aliphatic aldehydes which widen the scope of the present protocol. The reactions could be completed in short reaction time of 10–30 minutes. Isolation of the products was easy and the IL used could be easily recovered for reuse.
Experimental
Melting points were recorded in open capillaries. 1H-NMR and 13C NMR spectra recorded in a Bruker 300 MHz spectrometer and Bruker ascend 600 MHz spectrometer and Varian AS 400 (400 MHz) in CDCl3 with TMS as the internal standard. IR spectra were recorded in Perkin Elmer FT-IR 1600 spectrometer using KBr pallets. High resolution mass spectra were recorded on a Micromass QTOF ESI-MS instrument (model HAB273).
Preparation of IL
The classical ionic liquid was prepared by a method reported earlier.39
General procedure for synthesis of 9,9-dimethyl-12-aryl-8,9,10,12-tetrahydro-benzo[a]xanthenes-11-one
5,5-Dimethyl-cyclohexane-1,3-dione (dimedone) (1 mmol), 2-naphthol (1 mmol), aldehyde (1 mmol) and 50 mol% of di-n-propylammoniumhydrogensulphate were mixed, ground to a homogeneous mixture taken in a 100 mL RBF and heated to 80 °C with stirring in an oil bath for 15 minute. After completion of the reaction, indicated by TLC, the crude product was extracted with ethyl acetate, washed with water and dried in anhydrous Na2SO4. Product was crystallized on slow evaporation of solvent at room temperature. The ethyl acetate insoluble IL was recovered by simple filtration of product mixture and stored in desiccator for reuse.
General procedure for synthesis of 3,3,6,6-tetramethyl-9-aryl-1,2,3,4,5,6,7,8-octahydro-xanthene-1,8-dione
5,5-Dimethyl-cycloheaxan-1,3-dione (dimedone) (2 mmol), aldehyde (1 mmol) and 50 mol% IL was grounded to a homogeneous mixture taken in a 100 mL RBF and the mixture heated with stirring in an oil bath at 80 °C for 10 minutes. After completion of the reaction indicated by TLC, the crude product extracted with ethyl acetate, washed with water and then dried with anhydrous Na2SO4. Product was crystallized on room temperature evaporation of solvent. The ethyl acetate insoluble IL was recovered by simple filtration of product mixture and stored in desiccator for reuse.
General procedure for synthesis of 14-aryl-14[H]-dihydro-dibenzo[a,j]xanthenes
2-Naphthol (2 mmol), aldehyde (1 mmol) and IL (50 mol%) grounded to a homogeneous mixture taken in a 100 mL RBF and heated with stirring in an oil bath at 80 °C for 30 minutes. After completion of the reaction as indicated by TLC, the crude product was extracted with ethyl acetate, washed with water and dried with anhydrous Na2SO4. The product was crystallized on slow evaporation of solvent at room temperature. The ethyl acetate insoluble IL was recovered by simple filtration of the product mixture and stored in desiccator for reuse.
In all the reactions, the products were obtained in pure form and did not require further purification.
Recycling of ionic liquid
After completion of the reactions, ethyl acetate was added to the reaction mixture. The IL was found to be insoluble in ethyl acetate, precipitated out and recovered by simple filtration. Being hygroscopic, recovered IL was stored in desiccator and reused. The IL did not undergo any change during the reaction as confirmed by 1H NMR of the recovered IL (Fig. S2 in ESI†). Amount of the recovered IL is 0.0982 g (98.69%).
Experimental data
9,9-Dimethyl-12-(4-chlorophenyl)-8,9,10,12-tetrahydrobenzo[a]xanthe-11-one (1a). Mp: 182 °C (ethylacetate) (lit:26 181–182 °C); IR(KBr): ν 2950 (Ar–H), 2872 (C–H), 1657 (C
O), 1587 (C
C), 1362 (CH3), 1015 (C–O), 828 (Ar–H, out of plane bending), 748 (C–Cl) cm−1. 1H NMR (300 MHz, CDCl3): δH ppm 7.943–7.144 (10H, m, ArH) 5.709 (1H, s, CH), 2.567 (2H, s, CH2), 2.355–2.224 (2H, m, CH2), 1.123 (3H, s, CH3), 0.097 (3H, s, CH3). 13C NMR (75 MHz, CDCl3) δ ppm 196.94, 164.10, 147.72, 143.29, 131.93, 131.51, 131.21, 129.84, 129.14, 128.53, 128.43, 127.15, 125.06, 123.47, 117.08, 113.80, 50.85, 41.37, 34.21, 32.27, 29.36, 27.12. HRMS (ESI): m/z [M + Na]+ calcd for C25H21ClO2 411.1128, found 411.1131.
9,9-Dimethyl-12-(4-nitrophenyl)-8,9,10,12-tetrahydrobenzo[a]xanthen-11-one (1b). Mp: 176–177 °C (ethylacetate) (lit:27 178–180 °C); IR(KBr): ν 2952 (Ar–H), 2873 (C–H), 1650 (C
O), 1589 (C
C), 1509 (N
O), 1370 (CH3), 1223 (C–O), 1018 (C–O), 833 (Ar–H, out of plane bending) cm−1. 1H NMR (300 MHz, CDCl3): δH ppm 8.045–7.348 (10H, m, ArH), 5.822 (1H, s, CH), 2.602 (2H, s, CH2), 2.370–2.220 (2H, m, CH2), 1.139 (3H, s, CH3), 0.955 (3H, s, CH3). 13C NMR δ ppm 196.70, 164.62, 151.87, 147.80, 146.36, 131.59, 131.03, 129.63, 129.36, 128.66, 127.38, 125.24, 123.61, 123.11, 117.09, 116.04, 113.00, 50.79, 41.42, 34.87, 32.24, 29.28, 27.06. HRMS (ESI): m/z [M + Na]+ calcd for C25H21NO4 422.1368, found 422.1369.
9,9-Dimethyl-12-(4-methylphenyl)-8,9,10,12-tetrahydro-benzo[a]xanthen-11-one (1c). Mp: 177–179 °C (ethylacetate) (lit:27 176–178 °C); IR(KBr): ν 2945 (Ar–H), 2860 (C–H), 1650 (C
O), 1579 (C
C), 1445 (CH3), 1369 (CH3), 1219 (C–O), 1015 (C–O), 814 (Ar–H, out of plane bending) cm−1. 1H NMR (300 MHz, CDCl3): δH ppm 8.026 (1H, d, J = 8.1 Hz, ArH), 7.794–7.743 (2H, m, ArH), 7.473–7.235 (5H, m, CH2), 6.991 (2H, d, J = 7.8 Hz, ArH), 5.686 (1H, s, CH), 2.576 (2H, s, CH2), 2.353–2.223 (2H, m, CH2), 2.210 (3H, s, CH3), 1.126 (3H, s, CH3), 0.989 (3H, s, CH3). 13C NMR (75 MHz, CDCl3): δ ppm 196.96, 163.76, 147.58, 141.79, 135.61, 131.41, 131.34, 128.88, 128.66, 128.31, 128.21, 126.92, 124.80, 123.61, 117.81, 116.99, 114.30, 50.84, 41.33, 34.22, 32.24, 29.22, 27.21, 20.95. HRMS (ESI): m/z [M + Na]+ calcd for C26H24O2 391.1674, found 391.1678.
9,9-Dimethyl-12-(4-methoxyphenyl)-8,9,10,12-tetrahydrobenzo[a]xanthen-11-one (1d). Mp: 203–205 °C (ethylacetate) (lit:26 205–206 °C); IR(KBr): ν 2948 (Ar–H), 2863 (C–H), 1655 (C
O), 1570 (C
C), 1443 (CH3), 1351 (CH3), 1240 (C–O), 1027 (C–O), 824 (Ar–H, out of plane bending) cm−1. 1H NMR (300 MHz, CDCl3): δH ppm 7.996 (1H, d, J = 8.1 Hz, ArH), 7.795–7.742 (2H, m, ArH), 7.443–7.243 (5H, m, ArH), 6.712 (2H, d, J = 8.4 Hz, ArH), 5.663 (1H, s, CH), 3.692 (3H, s, OCH3), 2.570 (2H, s, CH2), 2.349–2.218 (2H, m, CH2), 1.122 (3H, s, CH3), 0.978 (3H, s, CH3). 13C NMR (75 MHz, CDCl3): δ ppm 197.08, 163.71, 157.71, 147.62, 137.13, 131.44, 131.33, 129.32, 128.68, 128.35, 126.92, 124.82, 123.65, 117.83, 117.00, 114.36, 113.53, 55.03, 50.87, 41.34, 33.77, 32.25, 29.26, 27.16. HRMS (ESI): m/z [M + Na]+ calcd for C26H24O3 407.1623, found 407.1624.
9,9-Dimethyl-12-phenyl-8,9,10,12-tetrahydro-benzo[a]xanthen-11-one (1e). Mp: 155 °C (ethylacetate) (lit:26 154–155 °C); IR(KBr): ν 2945 (Ar–H), 2870 (C–H), 1651 (C
O), 1591 (C
C), 1368 (CH3), 1229 (C–O), 804 (Ar–H, out of plane bending) cm−1. 1H NMR (300 MHz, CDCl3): δH ppm 8.031–7.068 (11H, m, ArH), 5.286 (1H, s, CH), 2.579 (2H, s, CH2), 2.353–2.225 (2H, m, CH2), 1.126 (3H, s, CH3), 0.973 (3H, s, CH3). 13C NMR (75 MHz, CDCl3): δ ppm 196.84, 163.81, 147.59, 144.62, 131.35, 131.26, 128.71, 128.30, 128.11, 126.88, 126.12, 124.77, 124.14, 123.54, 117.56, 116.92, 114.12, 50.75, 41.26, 34.57, 32.14, 29.18, 27.02. HRMS (ESI): m/z [M + Na]+ calcd for C25H22O2 377.1517, found 377.1519.
9,9-Dimethyl-12-naphthyl-8,9,10,12-tetrahydro-benzo[a]xanthen-11-one (If). Mp: 234–236 °C (ethylacetate) (lit:40 231–233 °C); IR(KBr): ν 2955 (Ar–H), 2869 (C–H), 1648 (C
O), 1582 (C
C), 1375 (CH3), 1222 (C–O), 1021 (C–O), 791 (Ar–H, out of plane bending) cm−1. 1H NMR (300 MHz, CDCl3): δH ppm 9.214 (1H, d, J = 7.2 Hz, ArH), 7.916 (1H, d, J = 8.1 Hz, ArH), 7.819–7.211 (11H, m, ArH), 6.455 (1H, s, CH), 2.638 (2H, s, CH2), 2.320–2.161 (2H, m, CH2), 1.132 (3H, s, CH3), 0.944 (3H, s, CH3). 13C NMR (75 MHz, CDCl3): δ ppm 197.12, 163.71, 147.54, 142.64, 133.49, 131.69, 131.33, 130.85, 128.62, 128.53, 128.28, 127.72, 127.14, 127.01, 126.21, 125.47, 125.40, 124.76, 124.57, 123.66, 119.48, 117.13, 115.10, 50.72, 41.46, 32.08, 30.16, 29.23, 27.11. HRMS (ESI): m/z [M + Na]+ calcd for C29H24O2 427.1674, found 427.1675.
9,9-Dimethyl-12-(2-methoxyphenyl)-8,9,10,12-tetrahydrobenzo[a]xanthen-11-one (1g). Mp: 165–167 °C (ethylacetate) (lit:27 163–165 °C); IR(KBr): ν 2955 (Ar–H), 2872 (C–H), 1658 (C
O), 1578 (C
C), 1445 (CH3), 1363 (CH3), 1245 (C–O), 1031 (C–O), 825 (Ar–H, out of plane bending) cm−1. 1H NMR (600 MHz, CDCl3): δH ppm 8.285 (1H, d, J = 8.4 Hz, ArH), 7.739–7.683 (2H, m, ArH), 7.430–7.251 (3H, m, ArH), 7.035–7.022 (1H, m, ArH), 6.812–6.768 (2H, m, ArH), 5.960 (1H, s, CH), 3.945 (3H, s, OCH3), 2.625–2.555 (2H, m, CH2), 2.281–2.190 (2H, m, CH2), 1.125 (3H, s, CH3), 1.001 (3H, s, CH3). 13C NMR (150 MHz, CDCl3): δ ppm 197.18, 164.59, 156.53, 147.84, 133.49, 132.05, 131.45, 130.79, 128.52, 128.36, 127.81, 126.92, 124.83, 124.16, 120.90, 118.49, 117.12, 113.84, 111.70, 56.04, 51.07, 41.63, 32.39, 29.68, 29.60, 27.16. HRMS (ESI): m/z [M + Na]+ calcd for C26H24O3 407.1623, found 407.1626.
9,9-Dimethyl-12-isopropyl-8,9,10,12-tetrahydro-benzo[a]xanthen-11-one (1h). Mp: 115–117 °C (ethylacetate) (lit:27 116–117 °C); IR(KBr): ν 2961 (Ar–H), 2849 (C–H), 1660 (C
O), 1559 (C
C), 1363 (CH3), 1200 (C–O) cm−1. 1H NMR (600 MHz, CDCl3): δH ppm 8.106 (1H, d, J = 8.4 Hz, ArH), 7.812 (1H, d, J = 7.8 Hz, ArH), 7.699 (1H, d, J = 9 Hz, ArH), 7.547–7.521 (1H, m, ArH), 7.439–7.413 (1H, m, ArH), 7.224 (1H, d, J = 9 Hz, ArH), 4.711 (1H, d, J = 3.6 Hz, CH), 2.622–2.296 (4H, m, 2CH2), 2.113–2.062 (1H, m, CH), 1.236 (3H, s, CH3), 1.143 (3H, s, CH3), 0.905 (3H, d, J = 7.2 Hz, CH3), 0.669 (3H, d, J = 6.6 Hz, CH3). 13C NMR (150 MHz, CDCl3): δ ppm 197.78, 167.33, 149.25, 131.66, 128.64, 128.00, 126.73, 124.90, 123.69, 119.11, 116.89, 111.84, 51.20, 41.73, 35.52, 33.08, 31.97, 30.10, 29.37, 27.42, 21.02, 18.42. HRMS (ESI): m/z [M + H]+ calcd for C22H24O2 321.1855, found 321.1849.
3,3,6,6-Tetramethyl-9-(4-chlorophenyl)-1,2,3,4,5,6,7,8-octahydroxanthene-1,8-dione (2a). Mp: 230–231 °C (ethylacetate) (lit:27 230–232 °C); IR(KBr): ν 2955 (Ar–H), 2877 (Ar–H), 2820 (C–H), 1662 (C
O), 1593 (C
C), 1362 (CH3), 1196 (C–O), 1161 (C–O), 840 (Ar–H, out of plane bending) cm−1. 1H NMR (300 MHz, CDCl3): δH ppm 7.252–7.148 (4H, m, ArH), 4.711 (1H, s, CH), 2.574 (4H, s, 2CH2), 2.271–2.134 (4H, m, 2CH2), 1.104 (6H, s, 2CH3), 0.988 (6H, s, 2CH3). 13C NMR (75 MHz, CDCl3): δ ppm 196.41, 162.43, 142.64, 131.98, 129.73, 128.85, 128.35, 128.18, 126.87, 117.00, 115.20, 50.62, 40.78, 32.17, 31.41, 29.24, 27.23. HRMS (ESI): m/z [M + Na]+ calcd for C23H25ClO3 407.1390, found 407.1392.
3,3,6,6-Tetramethyl-9-(4-nitrophenyl)-1,2,3,4,5,6,7,8-octahydroxanthene-1,8-dione (2b). Mp: 22–226 °C (ethylacetate) (lit:27 223–224 °C); IR(KBr): ν 2949 (Ar–H), 2868 (Ar–H), 2823 (C–H), 1666 (C
O), 1597 (C
C), 1512 (N
O), 1354 (CH3), 1200 (C–O), 1134 (C–O), 829 (Ar–H, out of plane bending) cm−1. 1H NMR (300 MHz, CDCl3): δH ppm 8.083 (2H, d, J = 8.4 Hz, ArH), 7.472 (2H, d, J = 8.4 Hz, ArH), 4.808 (1H, s, CH), 2.495 (4H, s, 2CH2), 2.277–2.120 (4H, m, 2CH2), 1.106 (6H, s, 2CH3), 0.974 (6H, s, 2CH3). 13C NMR (75 MHz, CDCl3): δ ppm 196.32, 162.95, 151.49, 146.29, 129.28, 123.33, 114.35, 50.46, 40.67, 32.26, 32.14, 29.15, 27.14. HRMS (ESI): m/z [M + Na]+ calcd for C23H25NO5 418.1630, found 418.1634.
3,3,6,6-Tetramethyl-9-(4-methoxyphenyl)-1,2,3,4,5,6,7,8-octahydroxanthene-1,8-dione (2c). Mp: 241–242 °C (ethylacetate) (lit:35 240–242 °C); IR(KBr): ν 2951 (Ar–H), 2882 (Ar–H), 2835 (C–H), 1666 (C
O), 1608 (C
C), 1362 (CH3), 1250 (C–O), 1192 (C–O), 840 (Ar–H, out of plane bending) cm−1. 1H NMR (300 MHz, CDCl3): δH ppm 7.202 (2H, d, J = 8.4 Hz, ArH), 6.755 (2H, d, J = 8.4 Hz, ArH), 4.693 (1H, s, CH), 3.733 (3H, s, OCH3), 2.455 (4H, s, 2CH2), 2.265–2.134 (4H, m, 2CH2), 1.098 (6H, s, 2CH3), 0.992 (6H, s, 2CH3). 13C NMR (75 MHz, CDCl3): δ ppm 196.57, 162.07, 157.89, 136.43, 129.28, 115.73, 113.42, 55.08, 50.71, 40.81, 32.18, 30.91, 29.26, 27.30. HRMS (ESI): m/z [M + Na]+ calcd for C24H28O4 403.1885, found 403.1887.
3,3,6,6-Tetramethyl-9-(4-hydroxyphenyl)-1,2,3,4,5,6,7,8-octahydroxanthene-1,8-dione (2d). Mp: 252–254 °C (ethylacetate) (lit:27 249–251 °C); IR(KBr): ν 3455 (O–H), 2952 (Ar–H), 2875 (Ar–H), 2830 (C–H), 1655 (C
O), 1595 (C
C), 1360 (CH3), 1220 (C–O), 1128 (C–O), 820 (Ar–H, out of plane bending) cm−1. 1H NMR (300 MHz, CDCl3): δH ppm 7.102 (2H, d, J = 7.8 Hz, ArH), 6.613 (2H, d, J = 8.1 Hz, ArH), 4.667 (1H, s, CH), 2.457 (4H, s, 2CH2), 2.273–2.145 (4H, m, 2CH2), 1.097 (6H, s, 2CH3), 0.996 (6H, s, 2CH3). 13C NMR (75 MHz, CDCl3): δ ppm 196.95, 162.27, 154.41, 135.95, 129.39, 115.81, 115.11, 50.73, 40.83, 32.22, 30.93, 29.20, 27.33. HRMS (ESI): m/z [M + Na]+ calcd for C23H26O4 389.1729, found 389.1731.
3,3,6,6-Tetramethyl-9-(4-methylphenyl)-1,2,3,4,5,6,7,8-octahydroxanthene-1,8-dione (2e). Mp: 216–217 °C (ethylacetate) (lit:27 213–215 °C); IR(KBr): ν 2939 (Ar–H), 2886 (Ar–H), 2825 (C–H), 1652 (C
O), 1616 (C
C), 1358 (CH3), 1200 (C–O), 1134 (C–O), 833 (Ar–H, out of plane bending) cm−1. 1H NMR (300 MHz, CDCl3): δH ppm 7.175 (2H, d, J = 7.8 Hz, ArH), 7.017 (2H, d, J = 7.5 Hz, ArH), 4.706 (1H, s, CH), 2.460 (4H, s, 2CH2), 2.238 (3H, s, CH3), 2.205–2.125 (4H, m, 2CH2), 1.096 (6H, s, 2CH3), 0.991 (6H, s, 2CH3). 13C NMR (75 MHz, CDCl3): δ ppm 196.42, 162.07, 141.12, 135.68, 128.71, 128.16, 115.65, 50.67, 40.77, 32.12, 31.35, 29.20, 27.28, 20.99. HRMS (ESI): m/z [M + Na]+ calcd for C24H28O3 387.1936, found 387.1937.
3,3,6,6-Tetramethyl-9-(3-chlorophenyl)-1,2,3,4,5,6,7,8-octahydroxanthene-1,8-dione (2f). Mp: 185–186 °C (ethylacetate) (lit:33 183–184 °C); IR(KBr): ν 2953 (Ar–H), 2877 (Ar–H), 2816 (C–H), 1666 (C
O), 1589 (C
C), 1365 (CH3), 1201 (C–O), 1165 (C–O), 843 (Ar–H, out of plane bending), 751 (C–Cl) cm−1. 1H NMR (300 MHz, CDCl3): δH ppm 7.222–6.963 (4H, m, ArH), 5.487 (1H, s, CH), 2.505–2.282 (8H, m, 4CH2), 1.234 (6H, s, 2CH3), 1.102 (6H, s, 2CH3). 13C NMR (75 MHz, CDCl3): δ ppm 190.60, 189.40, 140.42, 134.13, 129.34, 127.15, 126.00, 124.91, 115.06, 46.98, 46.36, 32.61, 31.40, 29.52, 27.33. HRMS (ESI): m/z [M + Na]+ calcd for C23H25ClO3 407.1390, found 407.1392.
3,3,6,6-Tetramethyl-9-(2,6-dichlorophenyl)-1,2,3,4,5,6,7,8-octahydroxanthene-1,8-dione (2g). Mp: 315–317 °C (ethylacetate) (lit:43 318–320 °C); IR(KBr): ν 2958 (Ar–H), 2872 (Ar–H), 2822 (C–H), 1661 (C
O), 1595 (C
C), 1359 (CH3), 1192 (C–O), 1160 (C–O), 839 (Ar–H, out of plane bending), 757 (C–Cl) cm−1. 1H NMR (300 MHz, CDCl3): δH ppm 7.382–6.984 (3H, m, ArH), 5.526 (1H, s, CH), 2.535 (4H, s, 2CH2), 2.264–2.129 (4H, m, 2CH2), 1.105 (6H, s, 2CH3), 1.051 (6H, s, 2CH3). 13C NMR (75 MHz, CDCl3): δ ppm 196.71, 163.87, 129.48, 128.74, 128.35, 127.83, 112.34, 50.71, 40.78, 31.85, 30.02, 29.16, 27.54. HRMS (ESI): m/z [M + Na]+ calcd for C23H24Cl2O3 441.1000, found 441.1004.
3,3,6,6-Tetramethyl-9-(2-hydroxy-5-nitrophenyl)-1,2,3,4,5,6,7,8-octahydroxanthene-1,8-dione (2h). Mp: 194–196 °C (ethylacetate) (lit: ---); IR(KBr): ν 3440 (O–H), 2934 (Ar–H), 2858 (Ar–H), 2830 (C–H), 1672 (C
O), 1581 (C
C), 1509 (N
O), 1355 (CH3), 1222 (C–O), 1125 (C–O), 831 (Ar–H, out of plane bending) cm−1. 1H NMR (600 MHz, CDCl3): δH ppm 10.325 (1H, s, OH), 8.059 (1H, dd, J = 3.0, 3.0 Hz, ArH), 7.941 (1H, d, J = 2.4 Hz, ArH), 7.130 (1H, d, J = 9 Hz, ArH), 4.675 (1H, s, CH), 2.631–2.363 (6H, m, 3CH2), 2.046–1.958 (2H, m, 1CH2), 1.035 (3H, s, 1CH3), 1.001 (3H, s, 1CH3), 0.996 (6H, s, 2CH3). 13C NMR (150 MHz, CDCl3): δ ppm 201.14, 196.05, 172.20, 168.14, 155.65, 144.54, 126.13, 123.96, 123.82, 117.88, 116.65, 111.18, 50.80, 50.10, 43.41, 41.44, 32.57, 31.37, 29.87, 29.40, 28.15, 27.27, 26.86. HRMS (ESI): m/z [M + Na]+ calcd for C23H25NO6 411.1128, found 411.1131.
3,3,6,6-Tetramethyl-9-methyl-1,2,3,4,5,6,7,8-octahydroxanthene-1,8-dione (2i). Mp: 176 °C (ethylacetate) (lit:55 174 °C); IR(KBr) ν 2834 (C–H), 1678 (C
O), 1590 (C
C), 1351 (CH3), 1175 (C–O) cm−1. 1H NMR (600 MHz, CDCl3): δH ppm 3.631 (1H, q, J = 6.6 Hz, CH), 2.343 (4H, s, 2CH2), 2.259 (4H, d, J = 3 Hz, 2CH2), 1.085 (3H, d, J = 3.6 Hz, CH3), 1.007 (12H, s, 4CH3). 13C NMR (150 MHz, CDCl3): δ ppm 197.32, 162.94, 116.97, 51.17, 41.05, 32.30, 29.48, 27.44, 21.97, 21.08. HRMS (ESI): m/z [M + H]+ calcd for C18H24O3 289.1804, found 289.1789.
3,3,6,6-Tetramethyl-9-phenethyl-1,2,3,4,5,6,7,8-octahydro-xanthene-1,8-dione (2j) (new compound). Mp: 172–174 °C (ethylacetate) (lit: -); IR(KBr): ν 2951 (Ar–H), 2838 (C–H), 1675 (C
O), 1585 (C
C), 1381 (CH3), 1171 (C–O) cm−1. 1H NMR (600 MHz, CDCl3): δH ppm 7.271–7.246 (2H, m, ArH), 7.176–7.126 (3H, m, ArH), 3.998 (1H, t, J = 7.8 Hz, CH), 2.498–2.471 (2H, m, CH2), 2.349–2.243 (10H, m, 5CH2), 1.070 (6H, s, 2CH3), 1.052 (6H, s, 2CH3). 13C NMR (150 MHz, CDCl3): δ ppm 190.23, 142.00, 128.57, 126.09, 116.56, 47.23, 46.42, 35.64, 31.67, 31.40, 29.92, 29.82, 26.96. HRMS (ESI): m/z [M + H]+ calcd for C25H30O3 379.2273, found 379.2222.
3,3,6,6-Tetramethyl-9-isopropyl-1,2,3,4,5,6,7,8-octahydroxanthene-1,8-dione (2k). Mp: 147–149 °C (ethylacetate) (lit:27 146–147 °C); IR(KBr): ν 2825 (C–H), 1675 (C
O), 1572 (C
C), 1353 (CH3), 1179 (C–O) cm−1. 1H NMR (600 MHz, CDCl3): δH ppm 3.455 (1H, d, J = 11.4 Hz, CH), 2.976–2.893 (1H, m, CH), 2.334–2.246 (8H, m, 4CH2), 1.007 (6H, s, 2CH3), 1.054 (6H, s, 2CH3), 0.840 (6H, d, J = 6 Hz, 2CH3). 13C NMR (150 MHz, CDCl3): δ ppm 190.57, 116.67, 47.21, 46.49, 38.29, 31.30, 30.17, 27.06, 25.93, 22.50. HRMS (ESI): m/z [M + H]+ calcd for C20H28O3 317.2117, found 317.2105.
14-(4-Chlorophenyl)-7,14-dihydro-dibenzo[a,j]xanthene (3a). Mp: 287 °C (ethylacetate) (lit:41 288 °C); IR(KBr):ν 2920 (Ar–H), 2820 (Ar–H), 1590 (C
C), 803 (Ar–H, out of plane bending) cm−1, 1H NMR (300 MHz, CDCl3): δH ppm 8.457 (2H, d, J = 8.4 Hz, ArH), 7.905–7.844 (4H, m, ArH), 7.664–7.450 (8H, m, ArH), 7.155 (2H, d, J = 8.4 Hz, ArH), 6.579 (1H, s, CH). 13C NMR (75 MHz, CDCl3): δ ppm 147.22, 142.73, 130.52, 129.86, 129.69, 128.47, 127.95, 127.64, 127.31, 125.88, 123.34, 121.53, 116.77, 115.51, 35.76. HRMS (ESI): m/z [M]+ calcd for C27H17ClO 392.0968, found 392.0971.
14-(4-Nitrophenyl)-7,14-dihydro-dibenzo[a,j]xanthene (3b). Mp: 312–314 °C (ethylacetate) (lit:41 315 °C); IR(KBr): ν 2941 (Ar–H), 2831 (Ar–H), 1595 (C
C), 1518 (N
O), 818 (Ar–H, out of plane bending) cm−1. 1H NMR (300 MHz, CDCl3): δH ppm 8.291 (2H, d, J = 8.4 Hz, ArH), 8.008 (2H, d, J = 8.7 Hz, ArH), 7.874–7.831 (4H, m, ArH), 7.700–7.421 (8H, m, ArH), 6.612 (1H, s, CH). 13C NMR (75 MHz, CDCl3): δ ppm 148.72, 131.03, 129.55, 129.02, 128.92, 127.15, 124.54, 123.83, 121.98, 118.02, 115.71, 37.82. HRMS (ESI): m/z [M]+ calcd for C27H17NO3 403.1208, found 403.1209.
14-(4-Methylphenyl)-7,14-dihydro-dibenzo[a,j]xanthene (3c). Mp: 229–230 °C (ethylacetate) (lit:41 227 °C); IR(KBr): ν 2909 (Ar–H), 2824 (Ar–H), 1593 (C
C), 1392 (CH3), 810 (Ar–H, out of plane bending) cm−1. 1H NMR (300 MHz, CDCl3): δH ppm 8.434 (2H, d, J = 8.4 Hz, ArH), 8.089–7.417 (12H, m, ArH), 6.997 (2H, d, J = 7.8 Hz, ArH), 6.481 (1H, s, CH), 2.196 (3H, s, CH3). 13C NMR (75 MHz, CDCl3): δ ppm 148.66, 142.15, 135.90, 131.46, 131.08, 129.19, 128.79, 128.12, 126.76, 124.22, 122.73, 118.01, 117.45, 37.64, 20.91. HRMS (ESI): m/z [M]+ calcd for C28H20O 372.1514, found 372.1517.
14-(4-Hydroxyphenyl)-7,14-dihydro-dibenzo[a,j]xanthene (3d). Mp: 145 °C (ethylacetate) (lit:41 141 °C); IR(KBr): ν 3459 (O–H), 2915 (Ar–H), 2830 (C–H), 1595 (C
C), 1230 (C–O), 804 (Ar–H, out of plane bending) cm−1. 1H NMR (300 MHz, CDCl3): δH ppm 8.325 (2H, d, J = 8.4 Hz, ArH), 7.860–7.796 (4H, m, ArH), 7.616–7.409 (8H, m, ArH), 7.112 (2H, d, J = 8.4 Hz, ArH), 6.472 (1H, s, CH). 13C NMR (75 MHz, CDCl3): δ ppm 148.74, 143.52, 132.13, 131.30, 131.10, 129.55, 129.14, 128.97, 128.70, 126.97, 124.42, 122.46, 118.07, 116.80, 37.43. HRMS (ESI): m/z [M]+ calcd for C27H18O2 374.1307, found 374.1309.
14-(2-Methoxyphenyl)-7,14-dihydro-dibenzo[a,j]xanthene (3e). Mp: 260 °C (ethylacetate) (lit:42 258–259 °C); IR(KBr): ν 2911 (Ar–H), 2828 (Ar–H), 1589 (C
C), 1395 (CH3), 815 (Ar–H, out of plane bending) cm−1. 1H NMR (600 MHz, CDCl3): δH ppm 8.575 (2H, d, J = 8.4 Hz, ArH), 7.794 (2H, d, J = 8.4 Hz, ArH), 7.758 (2H, d, J = 9 Hz, ArH), 7.543–7.518 (2H, m, ArH), 7.467 (2H, d, J = 9 Hz, ArH), 7.385 (2H, t, J = 7.8 Hz, ArH), 6.969–6.942 (1H, m, ArH), 6.901 (1H, s, CH), 6.861 (1H, d, J = 7.8 Hz, ArH), 6.633 (1H, t, J = 7.8 Hz, ArH), 4.271 (3H, s, OCH3). 13C NMR (150 MHz, CDCl3): δ ppm 153.95, 149.05, 132.25, 131.05, 128.65, 127.74, 126.83, 124.36, 123.50, 121.92, 118.72, 118.19, 110.78, 55.94, 30.45. HRMS (ESI): m/z [M]+ calcd for C28H20O2 388.1463, found 388.1465.
14-Methyl-7,14-dihydro-dibenzo[a,j]xanthenes (3f). Mp: 174 °C (ethylacetate) (lit:53 173 °C); IR(KBr): ν 2951 (Ar–H), 1565 (C
C), 1385 (CH3) cm−1. 1H NMR (400 MHz, CDCl3): δH ppm 8.246 (2H, d, J = 8.4 Hz, ArH), 7.881 (2H, d, J = 8.4 Hz, ArH), 7.773 (2H, d, J = 8.8 Hz, ArH), 7.636 (2H, t, J = 7.6 Hz, ArH), 7.466 (2H, t, J = 7.6 Hz, ArH), 7.380 (2H, d, J = 9.2 Hz, ArH), 5.446 (1H, q, J = 6.4 Hz, CH), 1.625 (3H, d, J = 7.2 Hz, CH3). 13C NMR (100 MHz, CDCl3): δ ppm 149.017, 131.492, 131.202, 129.074, 128.388, 126.939, 124.315, 122.386, 118.428, 118.031, 110.222, 26.538, 23.655. HRMS (ESI): m/z [M + H]+ calcd for C22H16O 297.1279, found 297.0925.
14-Isopropyl-7,14-dihydro-dibenzo[a,j]xanthene (3g). Mp: 152–153 °C (ethylacetate) (lit:50 152–153 °C); IR(KBr): ν 2939 (Ar–H), 1581 (C
C), 1372 (CH3), cm−1. 1H NMR (600 MHz, CDCl3): δH ppm 8.296 (2H, d, J = 8.4 Hz, ArH), 7.863 (2H, d, J = 8.4 Hz, ArH), 7.776 (2H, d, J = 8.4 Hz, ArH), 7.604–7.577 (2H, m, ArH), 7.449–7.406 (4H, m, ArH), 5.442 (1H, d, J = 4.2 Hz, CH), 2.312–2.248 (1H, m, CH), 0.819 (6H, d, J = 6.6 Hz, 2CH3). 13C NMR (150 MHz, CDCl3): δ ppm 151.10, 132.41, 131.24, 128.89, 128.23, 126.45, 124.20, 123.20, 117.79, 117.42, 37.24, 36.47, 20.55. HRMS (ESI): m/z [M + H]+ calcd for C24H20O 325.1592, found 325.1616.
Acknowledgements
Authors are thankful to Head, Department of Chemistry, GU for providing laboratory facilities. JD thanks CSIR, New Delhi, for Junior Research Fellowship. Central Instruments Facility, IIT Guwahati, is acknowledged for providing various instrumentation facilities. Authors are also grateful to Ms N. Phukan for analyzing the XRD data.
Notes and references
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Footnote |
† Electronic supplementary information (ESI) available: 1H and 13C NMR spectra of all the synthetic product. CCDC 1025707. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4ra12298d |
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