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

Abstract

A 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.

De novo assembly of frustrated Lewis pair bearing metal‐organic frameworks for atmospheric CO2 cycloaddition

“…It can be concluded that the acidic sites in FMOF-IBCIL are mainly imidazole ring and benzene ring from IBCIL and exposed open Cr(III) sites, 44 while the basic sites in FMOF-IBCIL are mainly Cl À . 45 The active sites in FMOF-IBCIL were further observed by using in-situ FT-IR spectroscopy for CO 2 adsorption with the assistance of DFT calculation. In the in-situ FT-IR spectra of CO 2 adsorption on FMOF-IBCIL, the ν 3 antisymmetric stretching band of CO 2 at 2359 cm À1 with four large shoulder peaks (2343, 2330, 2323, 2313 cm À1 ) can be observed (Figure 2A).…”