Solvent-Free Ball-Milling Biginelli Reaction by Subcomponent Synthesis

We report here an understanding of systems chemistry on small molecules through covalent mechanochemistry. As a proof-of-concept, the multicomponent Biginelli reaction by subcomponent synthesis was considered as a model system. Reactions were performed under solvent-free, metal-free, mechanochemical (ball milling) and ambient laboratory conditions. Br+-catalyzed oxidation of benzyl alcohols led to the product benzaldehydes and byproduct H+ which were further promoted as component and catalyst, respectively, for a cascade transformation to dihydropyrimidones within the same reaction pot. Remarkably, in solution, the reaction system could not be reproduced at room temperature even after 24 h.