Preparation of Spiro[indene-1,1′-isoindolin]-3′-ones via Sulfuric Acid-Promoted Cascade Cyclization

The sulfuric acid-promoted cascade cyclization of 2-(3-hydroxyprop-1-ynyl)­benzonitriles led to an efficient synthesis of spiro­[indene-1,1′-isoindolin]-3′-ones. This class of spiro compounds could also be prepared by the sulfuric acid-catalyzed cyclization of 2-(phenylacryloyl)­benzonitriles, which were readily derived from 2-(3-hydroxyprop-1-ynyl)­benzamides using trifluoroacetic acid as a catalyst.