Lactone Synthesis by Enantioselective Orthogonal Tandem Catalysis

Enantioselective Lactonization by π-Acid-Catalyzed Allylic Substitution: A Complement to π-Allylmetal Chemistry

Asymmetric allylic alkylation (AAA) is a powerful method for the formation of highly useful, non-racemic allylic compounds. Here we present a complementary enantioselective process that generates allylic lactones via π-acid catalysis. More specifically, a catalytic enantioselective dehydrative lactonization of allylic alcohols using a novel Pd^II -catalyst containing the imidazole-based P,N-ligand (S)-StackPhos is reported. The high-yielding reactions are operationally simple to perform with enantioselectivities up to 99 % ee. This strategy facilitates the replacement of a poor leaving group with what would ostensibly be a better leaving group in the product avoiding complications arising from racemization by equilibration.

Configuration Sampling With Five-Membered Atropisomeric P,N-Ligands

Here we report a strategy for the systematic variation of atropisomeric C₁ -symmetric P,N ligands to incrementally change the position of the groups within the chiral pocket without modifying their steric parameters. More specifically, the effects of systematic modification of the nitrogen heterocycle in atropisomeric C₁ -symmetric stack ligands have been investigated in this study. The versatility and applicability of this approach has been demonstrated in mechanistically distinct catalytic enantioselective transformations, resulting in the identification of a P,N-ligand for a highly enantioselective synthesis of organoboranes.