A novel chemoselective synthesis of 3H-spiro[isobenzofuran-1,3′-pyrazole] derivatives by oxidative cleavage of their corresponding dihydroindeno[1,2-c]pyrazoles

This paper reports a new and simple procedure for the synthesis of 3H-spiro[isobenzofuran-1,3′-pyrazole] derivatives by reacting 1-benzylidene-2-phenylhydrazine derivatives with ninhydrin in acetic acid medium at room temperature followed by oxidative cleavage of their corresponding dihydroindeno[1,2-c]pyrazoles. 1-Benzylidene-2-phenylhydrazine derivatives were prepared via the reaction between phenylhydrazine and benzaldehyde derivatives. Easy procedure, mild reaction conditions, high yields in short reaction times, availability of starting materials, and no formation of by-product are the advantages of this approach.