Stereodivergent Allylic Substitutions with Aryl Acetic Acid Esters by Synergistic Iridium and Lewis Base Catalysis

The
preparation of all possible stereoisomers of a given chiral
molecule bearing multiple stereocenters by a simple and unified method
is a significant challenge in asymmetric catalysis. We report stereodivergent
allylic substitutions with aryl acetic acid esters catalyzed synergistically
by a metallacyclic iridium complex and benzotetramisole. Through permutations
of the enantiomers of the two chiral catalysts, all four stereoisomers
of the products bearing two adjacent stereocenters are accessible
with high diastereoselectivity and enantioselectivity. The resulting
chiral activated ester products can be converted readily to enantioenriched
amides, unactivated esters, and carboxylic acids in a one-pot manner.