Highly Stereoselective Generation of Complex Oxy-Bicyclic Scaffolds via an Atom-Economic Pd(II)-Catalyzed Hydroalkynylation, Isomerization and Diels–Alder Cycloaddition Sequence

An atom-economic tandem Pd­(II)-catalyzed hydroalkynylation, alkyne-allene isomerization, and Diels–Alder cycloaddition is reported. The reaction employs readily available starting substrates, proceeds in a highly ordered fashion, features high regio- and stereoselectivity, and tolerates a wide range of functionality and structural motifs, thus offering an attractive strategy for producing new molecular complexity and diversity from easily available starting materials. A mechanistic study with density functional theoretical calculations was conducted to rationalize the observed stereoselectivity.