Nicolet 380 fourier transform infrared ftir spectrophotometer

All reagents and solvents were obtained from commercially available sources and were used without further purification. Reaction progress was monitored using analytical thin-layer chromatography (TLC) on precoated silica gel GF254 (Qingdao Haiyang Chemical Plant, Qing-Dao, China) plates and spots were detected under UV light (254 nm). Melting points were determined on a WRS-2B digital melting point apparatus and uncorrected. IR spectra were recorded using a Nicolet 380 Fourier-transform infrared (FTIR) spectrophotometer (Thermo, USA) from KBr pellets. ¹H NMR and ¹³C NMR spectra were recorded on a Bruker AVANCE III-600 NMR spectrometer (Bruker Biospin Co., Switzerland) with tetramethylsilane (TMS) as the internal standard and CDCl₃ as solvent and known chemical shifts of residual proton signals of deuterated solvents (¹H NMR δ: 7.26 for CDCl₃ and δ: 3.33 for H₂O) or carbon signals of deuterated solvents (¹³C NMR δ: 77.16 for CDCl₃) as internal standard. MS (ESI) measurement was conducted on an Agilent 1100 LC-MS spectrometer (Agilent, Palo Alto, USA).
The synthetic route of target molecules 7a–7o was depicted in Scheme 1. All the target compounds and some intermediates were synthesized according to the following procedures.