Paal--Knorr reactions are a classical method for synthesizing pyrroles, using 1,4-dicarbonyl compound and amine as reactants. It has the characteristics of green chemistry, as only two molecules of water are lost. In this teaching and learning experiment, 2,5-hexanedione and 4-"tert"-butylaniline were used to synthesize 1-(4-("tert"-butyl)phenyl)-2,5-dimethyl-1H-pyrrole without solvent and catalyst. This method offers several advantages, including commercially available starting materials, mild reaction conditions, solvent- and catalyst-free, short reaction time, simple and convenient operation, good yield, and high atom economy. The experiment allows beginners to master experimental skills including recrystallization, filtration, and NMR, as well as the concept of green chemistry. Green chemistry is important for environmental protection, resource conservation, and the sustainable development of the planet. Therefore, green chemistry experimental learning is also significant for undergraduates. We introduced green chemistry to students and encouraged them to discuss green chemistry and environmental protection. To assess students' understanding of green chemistry, they were asked to calculate the green metrics of the experiment to evaluate the sustainability of this process and answer the corresponding post-course questions. Results from a survey of students indicated an improved operation of the organic experiment and an enhanced knowledge of green chemistry.