Z. Karimi-Jaberi, A. Jaafarizadeh
Thus, a variety of synthetic approaches are desirable to synthesize acridines from
dimedone, aldehydes, and aniline derivatives, or ammonium acetate via the Hantzch
reaction in the presence of various catalysts [8–13]. In this context, we planned to
employ isatin instead of an aldehyde. However, recently, Kefayati’s group reported
the reaction of dimedone, anilines, and isatinin in the ionic liquid [HMIm]HSO4 at
80 °C. This reaction afforded 2-arylpyrrolo[2,3,4-kl]acridin-1(2H)-ones [14]. Also,
these compounds were constructed by refluxing a mixture of isatins and enaminones
in toluene in the presence of an L-proline catalyst [15].
The B(HSO4)3 catalyst was prepared by the addition of chlorosulfonic acid to
boric acid at room temperature according to our reported method [16]. This
catalyst is safe and easy to handle and has been successfully applied for the
synthesis of biscoumarins [16], dihydroquinazolinones [17], and arylidenebisamide
derivatives [18].
Experimental
The B(HSO4)3 catalyst was prepared by addition of chlorosulfonic acid to boric acid
at room temperature according to our reported method [14].
General procedure for the synthesis of pyrroloacridine derivatives
A solution of dimedone (2 mmol), aniline (1 mmol), isatin (1 mmol), and B(HSO4)3
(0.10 g) in 5.0 mL ethanol (96 %) was stirred at reflux conditions for the
appropriate times (Table 1). Upon completion of the reaction, monitored by TLC,
the reaction mixture was allowed to cool to room temperature. The solid was filtered
off and washed with water (2 9 10 mL) and purified by recrystalization from
ethanol. The structures of all products 4a–f were confirmed by IR, 1HNMR,
13CNMR, and elemental analysis.
Compound (4a): IR (KBr): 3,035, 2,960, 1,698, 1,647, 1,460, 1,344, 1,095,
777 cm-1; 1H NMR (400 MHz, CDCl3): 1.34 (s, 6H, 2CH3), 3.23 (s, 2H, CH2), 5.64
(s, 1H, CH), 7.43 (t, J 6.4 Hz, 1H), 7.51–7.56 (m, 4H), 7.68 (t, J 6.8 Hz, 1H), 7.78
(t, J 7.6 Hz, 1H), 8.19 (d, J 8.0 Hz, 1H), 8.76 (d, J 8.0 Hz, 1H); 13CMNR
(100 MHz, CDCl3): 32.0, 38.2, 45.3, 119.5, 122.5, 123.8, 125.4, 126.1, 127.5,
127.6, 128.6, 128.9, 130.5, 130.6, 134,5, 135.9, 150.9, 155.7, 167.7.
Compound (4b): IR (KBr): 3,064, 2,957, 1,699, 1,649, 1,494, 1,346, 1,090, 830,
775 cm-1; 1HNMR (400 MHz, CDCl3): 1.34 (s, 6H, 2CH3), 3.23 (s, 2H, CH2), 5.62
(s, 1H), 7.47 (d, J 8.4 Hz, 2H), 7.53 (d, J 8.4 Hz, 2H), 7.69 (t, J 7.2 Hz, 1H), 7.77 (t,
J 7.8 Hz, 1H), 7.19 (d, J 8.4 Hz, 1H), 8.72 (d, J 8.4 Hz, 1H).
Compound (4d): IR (KBr): 3,045, 2,961, 1,703, 1,648, 1,491, 1,344, 1,116, 1,076,
821, 773 cm-1; 1HNMR (400 MHz, CDCl3): 1.34 (s, 6H, 2CH3), 3.23 (s, 2H, CH2),
5.63 (s, 1H), 7.41 (d, J 8.4 Hz, 2H), 7.67–7.69 (m, 3H), 7.78 (t, J 7.2 Hz, 1H), 8.18
(d, J 8.4 Hz, 1H), 8.71 (d, J 8.0 Hz, 1H).
Compound (5) IR (KBr): 3,332, 3,090, 2,960, 1,724, 1,693, 1,599, 1,377, 1,233,
1
1,129, 905 cm-1; HNMR (400 MHz, CDCl3): 1.08 (s, 6H, 2CH3), 1.13 (s, 6H,
123