HOAc-Mediated Domino Diels–Alder Reaction for Synthesis of Spiro[cyclohexane-1,3′-indolines] in Ionic Liquid [Bmim]Br

An efficient and diastereoselective synthetic protocol for the construction of spiro­[cyclohexane-1,3′-indolin]-3-en-2′-ones and spiro­[cyclohexane-1,2′-inden]-3-ene-1′,3′-diones was provided by HOAc-mediated domino reaction of pinacoles with typical dienophiles, such as 3-methyleneoxindolines and 2-arylideneindane-1,3-diones, in ionic liquid [Bmim]­Br. This domino reaction involved the in situ generation of 1,3-dienes from acid-mediated dehydration of various pinacoles and the sequential Diels–Alder reaction.