Regio‐ and Stereo‐Selective Isomerization of Borylated 1,3‐Dienes Enabled by Selective Energy Transfer Catalysis

Abstract

AbstractConfigurationally‐defined dienes are pervasive across the bioactive natural product spectrum, where they typically manifest themselves as sorbic acid‐based fragments. These C5 motifs reflect the biosynthesis algorithms that facilitate their construction. To complement established biosynthetic paradigms, a chemical platform to facilitate the construction of stereochemically defined, functionalizable dienes by light‐enabled isomerization has been devised. Enabled by selective energy transfer catalysis, a variety of substituted β‐boryl sorbic acid derivatives can be isomerized in a regio‐ and stereo‐selective manner (up to 97 : 3). Directionality is guided by a stabilizing nO→pB interaction in the product: this constitutes a formal anti‐hydroboration of the starting alkyne. This operationally simple reaction employs low catalyst loadings (1 mol %) and is complete in 1 h. X‐ray analysis supports the hypothesis that the nO→pB interaction leads to chromophore bifurcation: this provides a structural foundation for selective energy transfer.