Scalable Enantiomeric Separation of Dialkyl-Arylphosphine Oxides Based on Host-Guest Complexation with TADDOL-Derivatives, and their Recovery

Several dialkyl-arylphosphine oxides were prepared, and the enantioseparation of the corresponding racemates was elaborated with host-guest complexation using TADDOL-derivatives. The crystallization conditions were optimized and two separate crystallization methods, one in organic solvent, and the other in water, were found to yield five examples of phosphine oxides with enantiomeric excess values higher than 94 %. A gram scale resolution was performed, and both enantiomers of the methyl-phenyl-propyl-phosphine oxide were separated with (R,R)- or (S,S)-spiro-TADDOL. The intermolecular interactions responsible for the enantiomeric recognition between the chiral host and guest molecules were investigated by single-crystal X-ray diffractional structural determinations. The similarities in the structural patterns of a few diastereomeric crystals were checked by powder X-ray diffraction, as well. Organic solvent nanofiltration (OSN) was used as a scalable technique for the decomposition of the corresponding phosphine oxide-spiro-TADDOL molecular complexes, and for the recovery of the phosphine oxide enantiomers and resolving agents.