Stereoselective synthesis of medicinally relevant furo[2,3-d]pyrimidine framework by thermal rearrangement of spirocyclic barbiturates

Abstract

A new rearrangement of functionalised cyclopropanes was found: the thermally initiated transformation of substituted 2-aryl-4,6,8-trioxo-5,7-diazaspiro[2.5]octanes in DMSO at 100 °C results in the formation of furo[2,3-d]pyrimidines in 50–75% yields. Similar results were obtained using [BMim][BF₄] as a solvent. NMR and single-crystal X-ray diffraction analysis indicate stereoselective formation of (5R*,6R*) isomers by thermal rearrangement of 2-aryl-1-cyano-5,7-dimethyl-4,6,8-trioxo-5,7-diazaspiro[2.5]octane-1-carboxylates.