Quantitative monitoring of solid phase organic reactions by high-resolution magic angle spinning NMR spectroscopy

Abstract

Three possible high-resolution magic angle spinning (HR MAS) NMR experiments to quantitatively monitor a solid phase supported Horner-Emmons reaction are presented. In the first experiment we follow the solid phase reaction in deuterated solvent directly in the NMR rotor. The second quantification is done by reconditioning of a few milligrams of resin from an undefined reaction vessel by washing, drying, and reswelling in deuterated solvent, and the evaluation of the amount of resin bound structures by comparing to an external standard. The third experiment represents the first analytical quantification of resin-bound structures without any sample preparation, except the transfer of resin-solvent suspension (large excess of reagents in protonated dimethylformamide) from the reaction vessel to the NMR rotor.