Solventless reaction methodology avoids the use of hazardous and toxic solvents and minimizes generation of waste, thereby addressing some of the principles of green chemistry. 2,4,6-Trisubstituted pyridines are readily prepared in high yield using this methodology in three steps: (i) solventless aldol condensation of benzaldehyde and acetophenone, (ii) solventless Michael addition of 2-acetylpyridine to the previously formed 1,3-diphenylpropenone, and (iii) the ring closure of the resulting 1,5-diketone in acetic acid with ammonium acetate. An undergraduate laboratory has been developed teaching the relevant principles of green chemistry, at the same time teaching traditional aspects of organic synthesis. The laboratory incorporates critical questions and demonstrates the advantages of the paradigm shift in using solventless reaction methodology compared to traditional approaches using organic solvents, as well as drawing attention to applications in other areas of chemistry including medicinal and supramolecular materials chemistry. The laboratory is inherently simpler and quicker, requiring less time and demand on equipment. All products and intermediates can be unambiguously characterized by NMR (1H and 13C) and IR spectrographic techniques.
|Journal||Journal of Chemical Education|
|Publication status||Published - 2005|