A detailed investigation into the one-pot cascade reaction of ethyl 3,9-dimethyl-7-phenyl-6H-dibenzo-[b,d]pyran-6-one-8-carboxylate with phenylhydrazine

摘要

When synthesizing cyclohexane-annulated pyrazolones from a cyclohexonedicarboxylate derivative with phenylhydrazine under the catalysis of sulfuric acid in the air, up to five products were finally obtained from the one-pot procedure. Among the obtained five products derived from the reaction, two unexpected products were identified, an interesting cyclohexane-annulated pyrazolone bearing a hydroperoxide group and a cyclohexene-annulated pyrazolone, both by crystallographic analysis. Reaction optimization and product distributions were investigated in different reaction conditions. A reaction mechanism for the formation of the five products has been proposed, and the two unexpected pyrazolones were suggested to be from the three-step cascade products of the condensation/amidation/peroxidation and the condensation/amidation/dehydration, respectively.