Copper-Catalyzed Reaction of α-Aryldiazoesters with Terminal Alkynes: A Formal [3 + 2] Cycloaddition Route Leading to Indene Derivatives

Abstract

It was discovered that Cu(IPr)Cl-catalyzed reaction of terminal alkynes with alpha-aryldiazoacetates provides indene derivatives, formal [3 + 2] cycloaddition adducts. Excellent regio- and chemoselectivity were observed to afford either 3H- or 1H-indene esters depending on the reaction conditions employed. The reaction is proposed to proceed via tandem processes: alkyne insertion into copper-carbenoid, intramolecular electrophilic attack on the aromatic ring, and then isomerization.