Tandem retro-Michael addition-Claisen rearrangement-intramolecular cyclization: One-pot synthesis of densely functionalized ethyl dihydropyrimidine-4-carboxylates from simple building blocks

摘要

Pyrolysis of suitably functionalized oxadiazoline diesters in refluxing xylenes provided ethyl 1,2-disubstituted 5-hydroxy-6-oxo-1,6-dihydropyrimidine-4-carboxylates in moderate to good yields. Under thermal conditions, the oxadiazoline esters undergo a sequence of complex molecular reorganizations, namely retro-Michael addition, Claisen rearrangement, and cyclization, to produce the desired pyrimidinones.