Catalytic Stereoselective 1,4‐Addition Reactions Using CsF on Alumina as a Solid Base: Continuous‐Flow Synthesis of Glutamic Acid Derivatives

Abstract

AbstractA novel methodology using CsF⋅Al2O3 as a highly efficient, environmentally benign, and reusable solid‐base catalyst was developed to synthesize glutamic acid derivatives by stereoselective 1,4‐addition of glycine derivatives to α,β‐unsaturated esters. CsF⋅Al2O3 showed not only great selectivity toward 1,4‐addtion reactions by suppressing the undesired formation of pyrrolidine derivations by [3+2] cycloadditions, but also offered high yields for the 1,4‐adduct with excellent anti diastereoselectivities. The catalyst was well characterized by using XRD, 19F MAS‐NMR and 19F NMR spectroscopy, FT‐IR, CO2‐TPD, and XPS. And highly basic F from Cs3AlF6 was identified as the most probable active basic site for the 1,4‐addition reactions. Continuous‐flow synthesis of 3‐methyl glutamic acid derivative was successfully demonstrated by using this solid‐base catalysis.