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.