Supramolecular Interactions as Key in Racemic Resolution: New Insights into the (SSi)- and (RSi)-Diastereomers of (1R,2S,5R)-Methyl(1-naphthyl)-phenylmenthoxysilane of Sommer

A highly selective approach with high yields of two diastereomeric silicon-stereogenic menthoxysilanes, (R-Si)-3 and (S-Si)-3, introduced by Sommer et al., could be established as well as investigated in detail using different analytical tools. Single-crystal X-ray diffraction analysis was used to examine the different crystallization rates while Hirshfeld surface analysis was applied to extend supramolecular interactions in the solid state which showed stronger hydrogen bridges for the faster crystallizing diastereomer (S-Si)-3. In addition, similar ground-state energies haven been found for both diastereomers by DFT calculations. Subsequent NMR studies showed stable Si-configurations wherein epimerization only started after more than 4 hours at 110 degrees C. Access to both diastereomers with opposite configuration at the stereogenic silicon center is achievable in high yields and high stereochemical purity using only naturally occurring (-)-menthol as a reagent.