Stereoselective Synthesis of 3-Alkylideneoxindoles by Palladium-Catalyzed Cyclization Reaction of 2-(Alkynyl)aryl Isocyanates with Organoboron Reagents
A palladium(0)/monophosphine catalystpromotes a cyclization reaction of 2-(alkynyl)aryl isocyanates with organoboron reagents to produce stereodefined 3-alkylideneoxindoles. The alkynyl and isocyanato groups undergo oxidative cyclization with Pd(0) to form an oxapalladacycle intermediate. Subsequent transmetalation and reductive elimination afford the product.