Nmr spectrophotometer

All solvents were obtained from Merck (Kenilworth, NJ, USA). The homogeneity of the compounds was checked by TLC performed on silica gel G; An iodine chamber was used for visualization of TLC spots. The FT-IR spectra were recorded in KBr pellets on a Spectrum BX Perkin Elmer FT-IR spectrophotometer (Perkin Elmer, Hopkinton, MA, USA). Melting points were determined on a Gallenkamp melting point apparatus (Gallenkamp, Loughborough, UK), and are uncorrected. NMR spectra were scanned in DMSO-d₆ on a Bruker NMR spectrophotometer (Bruker, Billerica, MA, USA) operating at 500 MHz for ¹H and 125.76 MHz for ¹³C at the Research Center, College of Pharmacy, King Saud University, Saudi Arabia. Chemical shifts δ are expressed in parts per million (ppm) relative to TMS as an internal standard and D₂O was added to confirm the exchangeable protons. Coupling constants (J) are in Hertz. The molecular masses of compounds were determined by UPLC/TQMS and all tested compounds yielded data consistent with a purity of ≥95%, as measured by HPLC (Agilent 1260 affinity). The elemental analyses (C, H, N (±0.4%); and S (±0.3%)) were performed on a CHN Elementar (Analysensysteme GmbH, Langenselbold, Germany).
The synthesis of dihydropyrimidine derivatives was carried out in single step as shown in Scheme 1.

All of the reagents used for synthesis of the novel hybrid compound were synthetic grade and purchased from known Aldrich and Merck companies. The solvent was obtained from Merck Company. The synthesized compounds were characterized with different spectroscopic techniques. KBr sample plates were used to obtain Infrared spectra by Jasco-680 FT-IR (Japan) spectrometer (FT-IR). Nuclear magnetic resonance (NMR) Spectrophotometer (Bruker 500 MHz, Germany) was utilized to record proton and carbon (¹H NMR & ¹³CNMR) spectra in DMSO‑d₆ with trimethyl silane as the internal reference. To obtain melting points of newly synthesized derivatives and to confirm the purity of the starting material, an electrothermal 9200 melting point apparatus (UK) was used. Additionally, silica gel 60 F254 plates (Merck, Germany) were applied in thin-layer chromatography (TLC) to assess the purity of the compounds and evaluate the reaction progression.

The ¹H-NMR experiments were carried out using a Bruker NMR spectrophotometer (Bruker Biospin GmbH, Karlsruhe, Germany) operating at 600 MHz and a temperature of 25 °C.

For structure prediction, ¹H and ¹³C proton nuclear magnetic spectra were recorded at 294 K on a 500 and 101 MHz nuclear magnetic resonance (NMR) spectrophotometer (Bruker, Germany). The samples were prepared as solutions in 100% CDCl₃, with 5 mg of RTE4 BS and tetramethylsilane (TMS) as internal standard (Pemmaraju et al., 2012 (link)).

All the chemicals were purchased from Sigma-Aldrich (Burlington, MA, USA), and commercial-grade solvents were used. Melting points of the synthesized compounds were checked with a Buchi B-540 melting point apparatus (New Castle, DE, USA). A Bruker NMR spectrophotometer (Billerica, MA, USA) was used to attain NMR spectra by using DMSO-d₆ and CDCl₃ solvents. Mass spectra were generated on a JEOL spectrometer JMS-HX-110 (USA). To monitor the reaction’s progress, TLC on silica gel 60 PF₂₅₄ cards (Merck, Kenilworth, NJ, USA) was used. UV light (254–365 nm) was used to visualize the product on TLC. For the purification of compounds, silica gel (70–230 mesh) was used in columns.

Melting points were determined uncorrected by a Gallen Kamp melting point apparatus (Sanyo Gallen Kamp, UK). Precoated silica gel plates (Kieselgel 0.25 mm, 60 F254, Merck, Germany) were used for TLC with solvent system of chloroform/methanol (8:2), spots were detected by UV light. IR spectra (KBr discs) were recorded using FT-IR spectrophotometer (Perkin Elmer, USA). ¹H, ¹³C NMR and 2D NMR experiments were scanned on an NMR spectrophotometer (Bruker AXS Inc., Switzerland), operating at 500 MHz for ¹H and 125.76 MHz for ¹³C. Chemical shifts are expressed in δ-values (ppm) relative to TMS as an internal standard, using DMSO-d₆ and CDCl₃ as solvents. EIMS were measured using Shimadzu-GC/MS. Elemental analyses were performed on a model 2400 CHNSO analyser (Perkin Elmer, USA). All the values were within ±0.4% of the theoretical values. The X-ray data were collected at T = 298 K on Enraf Nonius 590 Kappa CCD single crystal diffractometer equipped with graphite monochromated Mo Kα (λ=0.71073 Å) radiation using ψ–ω scan technique. All reagents used were of AR grade.