Thomas hoover melting point apparatus

General chemical reagents and solvents were obtained from commercial suppliers. All reactions were monitored by thin layer chromatography on plates coated with 0.25 mm silica gel 60 F254 (Qingdao Haiyang Chemicals, Qingdao, China). TLC plates were visualized by UV irradiation (254 nm, Shanghai Peiqing Sci & Tech, Shanghai, China). Flash column chromatography employed silica gel (particle size 32–63 μm, Qingdao Haiyang Chemicals, Qingdao, China). Melting points were determined with a Thomas-Hoover melting point apparatus (Thomas Scientific, Swedesboro, NJ, USA) and uncorrected. NMR spectra were obtained with a Bruker AV-400 instrument (Bruker BioSpin, Faellanden, Switzerland) with chemical shifts reported in parts per million (ppm, δ) and referenced to CDCl₃ or DMSO-d₆. The NMR spectra of compounds 11, 15, 16, 20–23, 25, and 27–29 were provided in Supplementary Materials (Figures S1–S22). IR spectra were recorded on a Bruker Vertex-70 spectrometer (Bruker Optics, Billerica, MA, USA). High-resolution mass spectra were reported as m/z and obtained with a Dalton micrOTOF-Q II spectrometer (Bruker Daltonics, Billerica, MA, USA).

The reagents were commercially purchased from Sigma-Aldrich (St. Louis, MO, USA) or TCI (Tokyo, Japan). If necessary, solvents were purified and/or dried prior to use. All anhydrous reactions were carried out under a dry atmosphere of nitrogen. Melting points (m.p.) were measured on Thomas-Hoover melting point apparatus (Thomas Scientific, Swedesboro, NJ, USA) and not corrected. ¹H, ¹³C-NMR and HMBC spectra were measured on a Varian 400 MHz spectrometer (Agilent Technologies, Santa Clara, CA, USA) in DMSO-d₆, CDCl₃, or (CD₃)₂CO. Chemical shifts (δ) are in ppm relative to tetramethylsilane, and coupling constants (J) are in Hz. DIP-MS (EI) was measured on an Agilent 7890A-5975C GC/MSD (Agilent Technologies). GC/MS (EI) was determined on a SHIMADZU QP 2010 model (Shimadzu, Kyoto, Japan) and FAB-MS was determined on a JEOL JMS-700 Mstation (JEOL, Tokyo, Japan). Fraction collection was performed on an EYELA fraction collector DC-1500 (Tokyo Rikakikai, Tokyo, Japan). An analytical TLC was performed on pre-coated silica gel 60 F₂₅₄ plates (Merck, Kenilworth, NJ, USA). Solvent systems for TLC and column chromatography were ethyl acetate/n-hexane mixtures and 10% methanol in dichloromethane. Column chromatography was carried out on Merck silica gel 9385 (Merck).