Determination of Dihydrobenzoacridinone Structures by NMR, IR, and UV Spectroscopy and Mass Spectrometry

Abstract

Introduction. Synthetic benzoacridinone derivatives are critical because of their applications as luminescent materials [1], antitumor drugs [2], and antibiotics [3]. The activity of such compounds was found to depend on the location of the carbonyl in the cyclic system [4]. Therefore, the location of the carbonyl in the fi nal product from three-component condensation of 2-naphthylamine, aromatic aldehydes, and dimedone is important because 9,9-dimethylor 10,10-dimethyl dihydrobenzoacridinones can be produced. The goal of the present work was to elucidate the structures of synthesized dihydrobenzoacridinone derivatives IVa–IVf. Experimental. 2-Naphthylamine (I, 1.43g, 0.01 mol), the appropriate aromatic aldehyde (IIa–IIf, 0.01 mol), and dimedone (III, 1.4 g, 0.01 mol) were refl uxed in EtOH until crystals of IVa–IVf began to precipitate (30–60 min) and then cooled. The resulting precipitate was fi ltered off, rinsed with Et2O, and recrystallized from EtOH:C6H6 (1:1). PMR and 13C NMR spectra were recorded from DMSO-d6 solutions (2–5%) on an Avance-500 spectrometer (BrukerBiospin, operating frequency 500.13 and 125.77 MHz for 1H and 13C). Chemical shifts were determined relative to TMS internal standard. COSY-45, NOESY, HSQC, and HMBC two-dimensional correlation spectra of IVa, IVd, and IVe were recorded in order to confi rm the structures and refi ne the resonances. All experimental results were obtained and processed using Topspin 2.1 software. IR spectra were recorded from thin layers or KBr pellets on a Protege-460 FTIR spectrophotometer (Nicolet). UV spectra of EtOH solutions (1·10–4 M) were taken on a Cary-300 spectrophotometer (Varian). Mass spectra of the synthesized compounds were measured using an Agilent 6890N gas chromatograph with an Agilent 5975 Inert mass-selective detector operating in electron-impact mode (70 eV) and was tuned to maximum sensitivity for the determined compounds. An HP-5ms capillary column (30 m × 0.25 mm × 0.25 μm) was connected directly to the mass spectrometer ion source. Samples were injected as CH2Cl2 solutions. Results and Discussion. Structures of synthesized 9,9-dimethyl-12-[5-(4-nitrophenyl)furan-2-yl]-9,10-dihydrobenzo[a] acridin-11-(7H,8H,12H)-one (IVa), 9,9-dimethyl-12-[5-(4-methoxy-2-nitrophenyl)furan-2-yl]-9,10-dihydrobenzo[a]acridin11-(7H,8H,12H)-one (IVb), 9,9-dimethyl-12-[5-(4-nitrophenyl)thiophen-2-yl]-9,10-dihydrobenzo[a]acridin-11-(7H,8H,12H)one (IVc), 9,9-dimethyl-12-[5-(3-nitrophenyl)thiophen-2-yl]-9,10-dihydrobenzo[a]acridin-11-(7H,8H,12H)-one (IVd), 12-[5-(4-bromophenyl)-1-methyl-1H-pyrrol-2-yl]-9,9-dimethyl-9,10-dihydrobenzo[a]acridin-11-(7H,8H,12H)-one (IVe), and 12-[5-(2-bromophenyl)-1-methyl-1H-pyrrol-2-yl]-9,9-dimethyl-9,10-dihydrobenzo[a]acridin-11-(7H,8H,12H)-one (IVf) were elucidated using UV, IR, PMR, and 13C NMR spectroscopy and mass spectrometry. The results indicated that condensation of 2-naphthylamine (I), aromatic aldehydes IIa–IIf, and dimedone (III) produced 9,9-dimethyl-12-[5-(aryl)furan-(or thiophen,