Palladium‐Catalyzed Enantioselective Heteroarenyne Cycloisomerization Reaction

Abstract

Abstract The extensively developed ene‐type enantioselective cycloisomerization of classical 1,n‐enynes provides an efficient approach to chiral cyclic 1,4‐dienes. In contrast, the catalytic asymmetric heteroarenyne (heteroarene–alkyne) cycloisomerization involving the dearomative transformation of endocyclic aromatic C=C bonds remains unknown. Herein, we communicate a PdH‐catalyzed enantioselective heteroarenyne cycloisomerization reaction of alkyne‐tethered indole substrates (formal 1,5‐ and 1,6‐enynes). Based on this strategy, a variety of structurally diverse chiral spiro and fused indoline derivatives bearing quaternary stereocenters and exocyclic C=C bonds are afforded in moderate to excellent yields and excellent enantioselectivities (up to 98 % ee). The classical ene‐type enantioselective 1,5‐enyne cycloisomerization of N ‐vinylpropiolamides is also developed to afford chiral 2‐pyrrolones in good to excellent ee values.