Synthesis, spectroscopic characterization, and reactivity of water-tolerant Eu3+-based precatalysts.

Abstract

We report the synthesis, spectroscopic characterization, and reactivity of Eu(3+) in the presence of a new set of chiral ligands designed for the aqueous, enantioselective Mukaiyama aldol reaction. Luminescence and NMR measurements were used to characterize the coordination environments of the Eu(3+)-based precatalysts, and this data is compared with yields and stereoselectivities. In addition to structure-function relationships, we found that, in the presence of excess hexadentate ligands, Eu(3+) is coordinatively saturated, and subsequently, the reactivity of the precatalysts is reduced. These findings are helpful for the design of new ligands that bind Eu(3+) without saturating the Eu(3+) coordination sphere.