From Star Anise Oil to (3+2) 1,3-Dipolar Cycloaddition Reactions: A Comprehensive Approach to the Extraction, Characterization, and Application of trans -Anethole with a Focus on Experimental Chemistry Education

This work describes an integrated undergraduate laboratory sequence combining essential oil extraction, spectroscopic characterization, and the synthetic application of trans-anethole in a (3+2) 1,3-dipolar cycloaddition reaction. These experiments involved three key steps: extraction, synthesis, and spectroscopic characterization. They were specifically designed for students studying Chemistry, Pharmacy, and Chemical and Food Engineering. To facilitate learning, the experiments were organized into two separate phases, allowing students to focus on each stage carefully and build a solid understanding of the processes involved. The first phase involved the extraction of star anise oil from star anise (Illicium verum Hook.f.) fruits, followed by the comprehensive characterization of the oil obtained, which is predominantly composed of trans-anethole. The second phase consisted of organic synthesis experiments using trans-anethole as the starting material for the preparation of 3,5-diarylisoxazolines through a (3+2) 1,3-dipolar cycloaddition reaction. In both phases, routine laboratory techniques were employed, together with full structural characterization by proton and carbon-13 nuclear magnetic resonance (1H and 13C NMR) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and high-resolution mass spectrometry (HRMS). In addition, SC-XRD analysis was performed on the final cycloadduct, with single crystals isolated for further structural analysis. The project can also be carried out in separate parts, with one focusing solely on the extraction process and the other exclusively on the synthesis process. In both cases, the laboratory procedures and spectroscopic characterization requirements are fulfilled.