The Synthesis of 2-Spiroindolin-3-one-(thio)barbiturates from 2,1-Benzisoxazoles: A Rearrangement Promoted by Thermal Conditions

A new thermal process to prepare spiroindolin-3-ones from 3-substituted 2,1-benzisoxazoles in good yields (70–85%) is described. The highest yields were observed when microwave irradiation was used. The method does not require the use of any additive or catalyst. A possible reaction mechanism involving a nitrene key intermediate is proposed.