Ferrocenium Boronic Acid Catalyzed Deoxygenative Coupling of Alcohols with Carbon- and Nitrogen-Based Borate and Silane Nucleophiles

A boronic acid catalyzed
carbon–carbon and carbon–nitrogen
bond-forming reaction for the functionalization of various π-activated
alcohols has been developed. Ferrocenium boronic acid hexafluoroantimonate
salt was identified as an effective catalyst in the direct deoxygenative
coupling of alcohols with a variety of potassium trifluoroborate and
organosilane nucleophiles. In a comparison between these two classes
of nucleophiles, the use of organosilanes leads to higher reaction
yields, increased diversity of the alcohol substrate scope, and high E/Z selectivity. Furthermore, the reaction
proceeds under mild conditions and yields up to 98%. Computational
studies provide a rationalization for a mechanistic pathway for the
retention of E/Z stereochemistry
when E or Z alkenyl silanes are
used as nucleophiles. This methodology is complementary to existing
methodologies for deoxygenative coupling reactions involving organosilanes,
and it is effective with a variety of organosilane nucleophile sub-types,
including allylic, vinylic, and propargylic trimethylsilanes.