Stereoselective Synthesis of Highly Substituted 1,3‐Dienes via “à la carte” Multifunctionalization of Borylated Dendralenes

Despite the high relevance of 1,3‐dienes, stereoselective methods to access tetrasubstituted conjugated dienes are still scarce. We here report an efficient and modular approach that provides access to multifunctional tetrasubstituted 1,3‐dienes with excellent levels of regio‐ and stereoselectivity. This methodology is based on a tetracomponent reaction between a borylated dendralene, an organolithium reagent and two different electrophiles. Mechanistic studies reveal that this transformation proceeds through a regio‐ and stereoselective carbolithiation/electrophilic trapping of an in situ formed dendralenic boron‐ate complex, followed by a stereoretentive halodeborylation. The ease in which complex structural dienes can be accessed and their synthetic versatility highlight the importance and utility of this method.