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.