Chiral Discrimination at the Solid State of Methyl 2-(Diphenylmethylsulfinyl)acetate

The present paper reports a study on the chiral discrimination at the solid state of methyl 2-(diphenylmethylsulfinyl)acetate (hereafter, DMSAM) as a key intermediate in the synthesis of an acetamide derivative (modafinil). A partial solid solution (i.e., stable “racemic conglomerate” with partial miscibility at the solid state) between enantiomers was characterized by X-ray single crystal analyses and high performance liquid chromatography (HPLC). Binary and ternary phase diagrams of DMSAM were investigated by HPLC measurements, differential scanning calorimetry (DSC), discontinuous isoperibolic thermal analysis (DITA), and Raman spectroscopy. Finally, the distribution of the two enantiomers inside single crystals was studied by dissolution and Raman microspectroscopy.