RESUMO
Configurationally-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 ß-boryl sorbic acid derivatives can be isomerized in a regio- and stereo-selective manner (up to 97 : 3). Directionality is guided by a stabilizing nOâpB interaction in the product: this constitutes a formal anti-hydroboration of the starting alkyne. This operationally simple reaction employs low catalyst loadings (1â mol %) and is complete in 1â h. X-ray analysis supports the hypothesis that the nOâpB interaction leads to chromophore bifurcation: this provides a structural foundation for selective energy transfer.