Comparing the Traditional with the Modern: A Greener, Solvent-Free Dihydropyrimidone Synthesis

A microscale organic synthesis experiment is outlined where students undertake both a "traditional" and "modern" Biginelli preparation of a dihydropyrimidone, within the same three-hour session. Each method is straightforward, appropriate as part of a mid-level undergraduate laboratory, and performed individually or between a pair of students. Emphasis is placed on comparing approaches from a green chemistry perspective. The class probes concepts of catalytic reactivity, solvent-free synthesis, atom economy, and energy consumption to assess green improvements made by employing the modern strategy.