Sequential Hydroperoxylation and Amberlyst‐15 Catalyzed Hock‐type Rearrangement of Spiroepoxy/Spiroaziridine Oxindoles for the Synthesis of 2‐Hydroxybenzo[b][1,4]oxazin‐3(4H)‐ones

Abstract

A sequential one‐pot direct strategy for the synthesis of 2‐hydroxy‐2‐substituted‐2H‐benzo[b][1,4]oxazin‐3(4H)‐ones is developed under ambient conditions with moderate to good yields (up to 75 %) by regioselective ring‐opening of spiro‐epoxy/aziridine oxindoles with 50 % aq. H2O2 followed by rearrangement reaction in presence of amberlyst‐15 catalyst. Further, sequential reaction with aldehydes/ketones and carbonyldiimidazole (CDI) gave spiro[benzo[b][1,4]oxazine‐2,4′‐[1,3]dioxolan]‐3(4H)‐ones and spiro[benzo[b][1,4]oxazine‐2,4′‐[1,3]dioxolane]‐2′,3(4H)‐diones, respectively.