One-Pot Synthesis of Benzo[4,5]imidazo[1,2-a]quinazoline Derivatives via Facile Transition-Metal-Free Tandem Process

Abstract

A one-pot transition metal-free method for synthesizing benzo[4,5]imidazo[1,2-a]quinazoline and imidazo[1,2-a]quinazoline derivatives has been developed. The approach is widely applicable to 2-fluoro-, 2-chloro-, 2-bromo- and 2-nitro-substituted aryl aldehyde and ketone substrates. The fluorescence properties of target compounds were studied.

Green Synthesis of 6‐Aryl‐5,6‐dihydrobenzo[4,5]imidazo[1,2‐c]quinazoline Derivatives in Ionic Liquid under Catalyst‐free Conditions

“…First of all, these optimized conditions were applied for the conversion of various kinds of benzaldehydes reacting with 2-(1H-benzo[d]imidazol-2-yl)aniline 1 into the corresponding 6-aryl-5,6-dihydrobenzo [4,5]imidazo[1,2-c]quinazoline analogues 3a-l (Scheme 2; Table 2, entries 1-12). From the Table 2, it could be found that the reaction could be suitable for benzaldehydes bearing electron-withdrawing groups (such as halide and cyano group) or electron-donating groups (such as alkoxy group).…”

“…It was reported that they were usually obtained by a condensation of 1H-benzo [d]imidazol-2-amine, aldehydes, and dimedone [3]; or 1H-benzo [d]imidazol-2-amine and 2-halogenated benzaldehydes [4]; or two-step reaction of isatoic anhydride, o-phenylenediamine, and aldehydes [5]. In addition, treatment of 2-(1H-benzo[d]imidazol-2-yl) aniline with various kinds of benzaldehydes also is a more efficient procedure.…”

“…Water in the filtrate was removed by distillation under reduced pressure, and the [BMIm]BF 4 in the residue could be reused after being evaporated at 80°C for 4 h in vacuum. Successive reuse of the recycled ionic liquids ([BMIm]BF 4 ) in the model reaction gave a high yield of 3a (92%) even after the fourth cycle.First of all, these optimized conditions were applied for the conversion of various kinds of benzaldehydes reacting with 2-(1H-benzo[d]imidazol-2-yl)aniline 1 into the corresponding 6-aryl-5,6-dihydrobenzo [4,5]imidazo[1,2-c]quinazoline analogues 3a-l (Scheme 2; Table 2, entries 1-12). From the Table 2, it could be found that the reaction could be suitable for benzaldehydes bearing electron-withdrawing groups (such as halide and cyano group) or electron-donating groups (such as alkoxy group).…”

“…Si as internal standard using a Bruker-400 spectrometer. HRMS analyses were carried out using a Bruker-micro-TOF-Q-MS analyzer.1 3-Cl 3a 9 9 6 2 2,3-Cl 2 3b 8 9 1 3 2,4-Cl 2 3c 8 9 8 4 2-Cl 3d 10 89 5 4-Cl 3e 12 92 6 3,4-Cl 2 3f 8 9 0 7 4-Br 3g 10 92 8 3-Br 3h 12 86 9 2-Br 3i 12 90 10 3,General procedure for the synthesis of 6-arylbenzo [4,5] imidazo[1,2-c]quinazoline derivatives 3.A dry 50-mL flask was charged with 2-(1H-benzo[d]imidazol-2-yl) aniline 1 (209 mg, 1.0 mmol), benzaldehydes 2 (1.05 mmol), and ionic liquid of [BMIm]BF 4 (2.0 mL). The reaction mixture was stirred at 80°C for 8-12 h, and then a little amount of water (5.0 mL) was added to the cooled mixture, and the generated yellow solid was filtered off.…”

“…Using ionic liquids as green media, a series of 6-arylbenzo [4,5]imidazo [1,2-c]quinazoline derivatives is synthesized via a reaction of 2-(1H-benzo [d]imidazol-2-yl)aniline and benzaldehydes in the air. While the intermediate products of 6-aryl-5,6-dihydrobenzo[4,5]imidazo [1,2-c]quinazolines were obtained in high yields at the same conditions under nitrogen protection.…”