Palladium-Catalyzed Enantiospecific Cross-Coupling of Secondary Alkyl Carbagermatranes Preserving Primary Alkyl Bpin

In this study, we report a series of enantioenriched, unactivated sp3-Ge/B bimetallic modules in which secondary alkyl carbagermatranes undergo enantiospecific palladium-catalyzed cross-coupling, while the vicinal primary alkylboron moiety is retained. This modular strategy provides access to alkylboronic esters bearing chiral, branched substituents that are valuable in medicinal chemistry. Mechanistic investigations reveal that the vicinal Bpin group does not promote transmetallation at the carbagermatrane center, highlighting the very high transmetallation propensity of alkyl carbagermatranes. Consequently, these organogermanium reagents address a long-standing challenge in cross-coupling chemistry: the intrinsically low transmetallation reactivity of unactivated secondary alkyl nucleophiles and their propensity for competing β-hydride elimination.