Site-Selective (Z)-α-Borylalkenyl Copper Systems for Nucleophilic Stereodefined Allylic Coupling

Stereoselective C-B and C-H Bonds Functionalization of PolyBorylated Alkenes

Alkenes are fundamental functional groups which feature in various materials and bioactive molecules; however, efficient divergent strategies for their stereodefined synthesis are difficult. In this regard, numerous synthetic methodologies have been developed to construct carbon-carbon bonds with regio- and stereoselectivity, enabling the predictable and efficient synthesis of stereodefined alkenes. In fact, an appealing alternative approach for accessing challenging stereodefined alkene molecular frameworks could involve the sequential selective activation and cross-coupling of strong bonds instead of conventional C-C bond formation. In this study, we introduce a series of programmed site- and stereoselective strategies that capitalizes on the versatile reactivity of readily accessible polymetalloid alkenes (i.e. polyborylated alkenes), through a tandem cross-coupling reaction, which is catalyzed by an organometallic Rh-complex to produce complex molecular scaffolds. By merging selective C-B and remote C-H bond functionalization, we achieve the in situ generation of polyfunctional C(sp2)-nucleophilic intermediates. These species can be further modified by selective coupling reactions with various C-based electrophiles, enabling the formation of C(sp2)-C(sp3) bond for the generation of even more complex molecular architectures using the readily available starting polyborylated-alkenes. Mechanistic and computational studies provide insight into the origins of the stereoselectivities and C-H activation via a 1,4-Rh migration process.

Ru(0)-catalysed synthesis of borylated polyene building blocks by cross-dimerisation toward cross-coupling

Conjugated and non-conjugated polyenes are important substructures and are often found in biologically active compounds and natural products. Their preparation often needs multiple steps or iterative reactions and as a result, they have poor step economies. In this feature article, we show a new methodology to prepare these substructures by combinations of cross-dimerisation giving borylated polyenes and subsequent cross-coupling reactions. This divergent reaction strategy allows for the opportunity to access many bioactive compounds and natural products as well as some electronic materials.

Stereoselective Control of the Cu Activation of β,β-Diboryl Acrylates for Allylic Coupling Protocols with Concomitant Lactonization

The key to a successful C-B activation is to discriminate between two geminal boryl moieties that are exposed to the same reaction conditions. Here we describe a stereoselective C-B activation of β,β-diboryl acrylates forming exclusively the (Z)-α-borylalkenyl copper(I) key intermediate, for subsequent allylic alkylation reactions. The new borylated (Z)-skipped dienoates followed a feasible iodo-lactonization sequence for the preparation of borylated lactone cores, which can be used in drug discovery.