Novel synthesis of highly functionalized pyrazolone systems via rearrangement of 5-phenyl-1-oxa-5,6-diazaspiro[2.4]heptane-4,7-diones
Epoxidation of 4-alkylidene(arylidene)-1-phenyl-3,5-pyrazolidinediones using alkaline hydrogen peroxide gave the corresponding 5-phenyl-1-oxa-5,6-diazaspiro[2.4]heptane-4,7-dione derivatives. Their reaction with nucleophilic reagents was investigated. The resulting products depend on the type of the diazaspiro compound and/or the nucleophile used.