The two acridinedione derivatives 1 [3,3,6,6-tetramethyl-9-(4-methoxyphenyl)-3,4,6,7,9,10-hexahydro-2H,5H-acridine-1,8-dione (C24H29NO3)] and 2 [3,3,6,6-tetramethyl-9-(4-methylphenyl)-3,4,6,7,9,10-hexa-hydro-2H,5H-acridine-1,8-dione (C24H29NO2)] were synthesized and their crystal structures were determined by direct methods. The asymmetric unit of compound 1 contains two independent molecules. The 1,4-dihydropyridine (DHP) ring adopts boat conformation in both 1 and 2. In 1 the dione rings exist in sofa conformation (for both the crystallographically independent molecules) while the corresponding rings in 2 adopt half chair and sofa conformations, respectively. The crystal packing is stabilized by intermolecular N–HO and C–HO interactions in compound 1 and N–HO interactions in compound 2.

1. Introduction

A multicomponent reaction (MCR) provides powerful tool for the synthesis of complex molecules and drug like heterocycles and has great interest in diversity oriented synthesis. MCRs are economic, selective, plain procedure and time and power saving with being ecofriendly in organic synthesis [13]. Acridinediones containing a 1,4-DHP nucleus are used as laser dyes with very high efficiencies of photo initiators [4, 5]. A latest literature review reveals that 1,4-DHP nucleus exhibits calcium channels blockers and antiaggregatory activity. Besides this, 1,4-DHP skeleton shows many biological activities such as antihypertension, anticancer, antidiabetics, geroprotective, neuroprotectant, and anti-HIV [6]. Synthesis of 1,8-dioxoacridinedione is usually carried out by MCRs of dimedone, aldehydes, and ammonium acetate [7, 8]. In continuation of our ongoing work on multicomponent reaction derivatives and their crystal structure analyses [9, 10], we report the synthesis and crystal structure of 3,3,6,6-tetramethyl-9-(4-methoxyphenyl)-3,4,6,7,9,10 hexahydroacridine-1,8-dione 1 and 3,3,6,6-tetramethyl-9-(4-methylphenyl)-3,4,6,7,9,10 hexahydroacridine-1,8-dione 2 (Scheme 1).


2. Materials and Methods

All the chemicals were purchased from SD Fine Chem Limited and Thomas Baker, used as received without further purification. Melting point was determined on Labstar melting apparatus. The IR spectra were recorded on a Perkin-Elmer, FTIR-1600 spectrophotometer and expressed in cm−1 (KBr). 1H NMR spectra were recorded on Bruker Avance (300 MHz) spectrometer in DMSO-d6 using TMS as the internal standard. Elemental analysis was performed on a EURO-EA analyzer.

2.1. Synthesis of 3,3,6,6-Tetramethyl-9-(4-methoxyphenyl)-3,4,6,7,9,10-hexahydroacridine-1,8-dione (1) and 3,3,6,6-Tetramethyl-9-(4-methylphenyl)-3,4,6,7,9,10-hexahydroacridine-1,8-dione (2)

In a 50 mL rounded bottom flask, a mixture of dimedone (2 mmole), 4-methoxy or 4-methyl benzaldehyde (1 mmole), and ammonium acetate (1.2 mmole) in mixture of aqueous ethanol (5 mL) was stirred at RT for 5 min. To this [CMIM][HSO4] (20 mol%) was added and the reaction mixture heated at 85°C till completion of reaction. The progress of reaction was monitored by TLC. After completion of reaction, the mixture was gradually cooled to RT and poured on ice water under stirring; solids were precipitated out. Filter the product and dry it. The crude products were recrystallized from ethanol and characterized by IR, 1H NMR, and elemental and single crystal analysis.

Compound 1M.P.: 308–311°C, Yield: 80%.IR (KBr): 3431, 3298, 2963, 1657, 1619 cm−1.1H NMR (300 MHz, DMSO-d6): 1.03 (s, 6H, CH3), 1.15 (s, 6H, CH3), 2.31–2.43 (m, 8H, CH2), 3.92 (s, 3H, OCH3), 5.01 (s, 1H, CH), 6.78–7.31 (m, 4H. Ar–H), 8.97 (bs, 1H, NH).Analysis calculated for C24H29NO3 (379.491): C, 75.96%; H, 7.70%; N, 3.69%.Found: C, 75.91%; H, 7.64%; N, 3.74%.

Compound 2M.P.: 325–327°C, Yield: 85%.IR (KBr): 3415, 3298, 2959, 1641, 1613 cm−1.1H NMR (300 MHz, DMSO-d6): 0.98 (s, 6H, CH3), 1.08 (s, 6H, CH3), 2.19 (s, 3H, CH3), 2.23–2.41 (m, 8H, CH2), 5.08 (s, 1H, CH), 6.97–7.21 (m, 4H. Ar–H), 8.72 (bs, 1H, NH).Analysis calculated for C24H29NO2 (363.429): C, 79.30%; H, 8.04%; N, 3.85%.Found: C, 79.26%; H, 7.99%; N, 3.90%.

2.2. X-Ray Analysis

A summary of the crystallographic data is given in Table 1. The X-ray intensity data of a well-defined crystal for 1 and 2 (0.30 0.20 0.10 mm) were collected at room temperature (293 K) by using a CCD area-detector diffractometer (X’calibur system, Oxford diffraction, 2010) which is equipped with graphite monochromated MoK radiation ( Å). The cell dimensions were determined by the least-squares fit of angular settings of 14203 (1) and 11474 (2) reflections in the range 3.48 to 29.04° (1) and 3.99 to 23.48° (2), respectively. Data were corrected for Lorentz, polarization, and absorption factors.

The structure elucidation and full-matrix least-squares refinement were carried out by using SHELXL97 software [11]. The geometry of the molecule is determined by PLATON [12]. All the hydrogen atoms were geometrically fixed and allowed to ride on the corresponding non-H atoms with C-H distances of 0.93–0.98  and with , except for the methyl groups where (H) = 1.5(C). Multiscan absorption correction was employed (with = 0.65162 (1); 0.90012 (2) and = 1.00000 (for both 1 and 2, resp.)) [13]. Atomic scattering factors were taken from International Tables for X-Ray Crystallography (1992, Vol. C, Tables and The crystallographic data are summarized in Table 1. CCDC-946763 (1) and CCDC-954009 (2) contain the supplementary crystallographic data for both the structures.

3. Results and Discussion

Figures 1 and 2 show the perspective view of molecules 1 and 2, respectively [14]. Table 2 presents selected geometrical parameters for both the structures. The asymmetric unit of compound 1 comprises two crystallographically independent molecules, A and B (Figure 2). Bond lengths and angles are normal and correspond to those observed in some related structures [15, 16]. The central ring (C9/C10/C11/N12/C13/C14) of the acridinedione moiety adopts a distorted boat conformation molecule A: Cs (C9A–C12A) = 2.426 and Cs (C10A–C11A) = 7.72; molecule B: Cs (C9B–C12B) = 1.014 and Cs (C10B–C11B) = 11.97. The benzene ring is held almost at right angles to the 1,4-DHP ring (dihedral angles for molecules A and B being 87.32(13)° and 86.49(12)°, resp.). A comparison of 1,4-DHP ring is presented in Table 3. Both the cyclohexanes exist in sofa conformations (molecule A: Cs (C3A) = 4.97; Cs (C6A) = 9.625; molecule B: Cs (C3B) = 6.917; Cs (C6B) = 10.82)) [17].

In molecule 2, the central ring (C9/C10/C11/N12/C13/C14) of the acridinedione moiety adopts a boat conformation (ΔCs (C9–C12) = 2.22 and ΔCs (C10-C11) = 3.757). The cyclohexane comprising atoms (C5/C6/C7/C8/C14/C13) adopts half chair conformation (ΔC2 (C13-C14) = 9.63) while the other one exists in sofa conformation (ΔCs (C10–C3) = 1.85) [17]. The dihedral angle between the 1,4-DHP ring and the phenyl ring (C19–C24) is 89.15(9)°, which shows that the benzene ring is almost perpendicular to the central 1,4-dihydropyridine ring. The bond lengths of C11–N12 and C13–N12 are 1.354(3)  and 1.376(3) , respectively, shorter than the normal C–N bond length of 1.47 .

Packing of molecules 1 and 2 in the unit cell is shown in Figure 3. The crystal packing is stabilized by the presence of few intermolecular N–HO and C–HO interactions in compound 1 and a N–HO interaction in compound 2, respectively (Table 4).

4. Conclusions

Compounds (1) and (2) were synthesized by adopting multicomponent reaction system and the corresponding molecular and crystal structures were determined by single crystal X-ray diffraction. In compound 1 there are two independent molecules per asymmetric unit. The 1,4-dihydropyridine ring adopts boat conformation in both compounds 1 and 2. In addition the cyclohexane rings display sofa conformations for both molecules A and B in compound 1 whereas in 2 the cyclohexane ring (C5/C6/C7/C8/C14/C13) adopts half chair conformation and the other ring adopts sofa conformation.

Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.


One of the authors (Rajni Kant) acknowledges the Department of Science & Technology for sanctioning single crystal X-ray diffractometer as a National Facility under Project no. SR/S2/CMP-47/2003.