The development of new robust and reliable transformations is of utmost importance for the efficient synthesis of fine chemicals. For instance, the discovery of new pharmaceuticals and agrochemicals requires the synthesis of libraries of molecules that exhibit promising activities, typically complex molecules containing multiple functional groups. In that context, the access to organoboron derivatives of such lead molecules is highly appealing because they can be readily converted to families of derivatives through divergent post-functionalization reactions exploiting the unique reactivity of their C-B bonds. Ideally, such organoboron intermediates can be prepared by borylation of a single C−H bond in available starting materials, thereby allowing the direct derivatization of existing libraries of bioactive compounds. While the borylation of aromatic C(sp2)-H and aliphatic C(sp3)-H bonds has attracted a lot of attention resulting in sizeable progress, the C-H borylation of alkenes remains underdeveloped and suffers from persistent issues restricting its application in fine-chemical synthesis, despite the great synthetic utility of the corresponding vinyl boronate esters.
Transfer borylation for late-stage functionalization
Transfer C−H borylation of alkenes bears the potential to unlock a range of attractive transformations for modular synthesis and late-stage derivatization of complex molecules. However, its scarce precedence and limited mechanistic understanding hinder the development of practical synthetic protocols. Based on the mechanistic design, we have recently discovered a highly efficient a Rh(I)-catalyzed transfer C−H borylation that is applicable to various terminal and internal alkenes and compatible with a plethora of functional groups, including often problematic motifs (Chem Catalysis 2022, (in press): DOI: 10.1016/j.checat.2022.02.008).
Having the insight into the features controlling the activity and the selectivity of the transfer C-H borylation reactions, we foresee the possibility to attain the catalysts that would selectively form other regio- and stereoisomers of the products, which are typically difficult to obtain with existing methods. Research along these lines is continued.