Synthesis of chromeno[2,3-b]indeno[2,1-e]pyridine derivatives via K₂CO₃-promoted three-component reaction of 2-amino-4H-chromen-4-ones, aromatic aldehydes and 1H-Indene-1,3(2H)-dione

Abstract

S2 EXPERIMENTAL SECTIONGeneral. Substituted 2-amino-4H-chromen-4-ones 1a-f were prepared according to reported methods [11] and were purified by recrystallization from ethanol. Common reagents and solvents were purchased from commercial suppliers. Melting points were recorded in a Yanaco melting point apparatus and are uncorrected. TLC was carried out on pre-coated glass plates, and components were monitored by observation under UV light (254 and 365 nm). Flash chromatography was employed on silica gel (230-400 mesh) eluting with ethyl acetate-hexanes mixture. IR spectra were recorded using a Nicolet FT-IR 5DX spectrometer and samples were loaded neat. The 1 H and 13 C NMR spectra were recorded on a Bruker AV-400 spectrometer with TMS as internal reference in CDCl3. Chemical shifts were quoted in ppm. Coupling constants, J, were shown in Hz. HRMS analysis was carried out on a UHR-TOF maXis mass spectrometer in ESI mode. Data collection for the crystal structure was performed using a SMART APEX-II diffractometer with monochromatic Mo KR radiation (λ) 0.71073 Å) and integrated with the SAINT-Plus program. All calculations were performed with programs from the SHELXTL crystallographic software package.The mixture of substituted 2-amino-4H-chromen-4-ones 1a-f (1.0 mmol), aromatic aldehydes 2a-l (2.0 mmol), 1H-indene-1,3(2H)-dione (3a) (292 mg, 2.0 mmol) and potassium carbonate (166 mg, 1.2 mmol) in DMF (8 mL) was stirred at 110 o C in oil bath for 8-11 h. The reaction was monitored by TLC (EtOAc/hexanes, 1/2, silica gel). After complete consumption of 2-amino-4H-chromen-4-ones, most of solvent was removed by reduced pressure distillation. To the cooled residues were added water (15 mL), subsequently the resulting mixture was fully stirred. Then, the resulting mixture was extracted with dichloromethane (10 mL × 2). The combined organic phase was washed with water (10 mL) and brine (10 mL), and dried over anhydrate sodium sulfate. After removal of dichloromethane via vacuum, the crude product was purified by flash chromatography (EtOAc/hexanes, 1/10, silica gel) to give the desirable products 4a-t.