Copper-Catalyzed Tandem Decyclization-Cyclization Reaction of N-Alkynyl-3-hydroxyisoindolin-1-ones Generated from N-Alkynyl Phthalimides: Selective Synthesis of ortho-(2-Oxazolyl)phenyl Ketones

Selective carbophilic monoaddition on N-alkynyl phthalimides was performed with organometallic reagents to afford 3-substituted N-alkynyl-3-hydroxyisoindolin-1-ones (α-hydroxy ynamides) as a new subgroup of ynamides. Owing to the alkynyl motif on the nitrogen atom, α-hydroxy ynamides were easily isomerized to the corresponding ortho-(2-oxazolyl)phenyl ketones in a CuCl-catalyzed tandem decyclization–cyclization reaction under mild conditions.