Indomuscone-Based Sterically Encumbered Phosphines as Ligands for Palladium-Catalyzed Reactions

The fragrance compound indomuscone is used here as a scaffold to prepare two different sterically hindered phosphines, one aromatic and another alkylic, in good yields, after four synthetic steps. The new phosphines show enhanced electronic and steric properties when compared to benchmark commercial phosphine ligands, which is reflected in the catalytic results obtained for representative palladium-catalyzed reactions such as the telomerization reaction, the Buchwald-Hartwig and Suzuki cross-coupling reactions of chloroaromatic rings, and the semi-hydrogenation reaction of an alkyne. In particular, the indomuscone-based aromatic phosphine ligand leads to the highest selectivity for the tail-to-head telomerization product between isoprene and methanol, while the indomuscone-based alkylic phosphine ligand shows extraordinary similarities with the Buchwald-type SPhos phosphine ligand.