Organic Superbases in Annulation with Propargylic Alcohols: Straightforward Synthesis of the Functionalized Oxazolopyrrolohexahydropyrimidine and Oxazolohexahydropyrimidoazepine Scaffolds

摘要

The popular organic superbases 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) underwent annulation with electron-deficient propargylic alcohols [EWG = CN, C(O)Ph, CO2Me] to afford functionalized condensed hexahydropyrimidine systems, [1,3]oxazolo[3,2-a]pyrrolo[2,1-b]hexahydropyrimidines and [1,3]oxazolo[3,2:3,4] hexahydropyrimido[1,2-a]azepines, in good to high yields. The reactions proceeded regioselectively and, in most cases, stereoselectively under mild conditions (without catalyst, 20-25 degrees C). The synthesized compounds, owing to their potential rich chemistry, are novel promising precursors for pyrimidine-based pharmaceuticals.