Copper-Catalyzed Ring-Opening Defluoroborylation of <i>gem</i>-Difluorinated Cyclobutenes: A General Route to Bifunctional 1,3-Dienes and Their Applications
gem-fluorinated cyclobutenes with bis(pinacolato)diboron (B2pin2). A sequence of defluoroborylation and a ring-opening process produces B,F-bifunctional 1,3-dienes in a stereoselective manner. The transformation together with the efficient downstream coupling of the boronate and the fluoride moieties collectively constitutes a modular route to highly functionalized and stereocontrolled 1,3-dienes.