Optically Pure Calixarenyl Phosphine via Stereospecific Alkylation on Evans' Oxazolidinone Moiety.

A convenient protocol for the synthesis of 25,26,27-tribenzoyl-28-[(( S )-1-diphenylphos- phanyl-propan-2-yl)oxy]-calix[4]arene via stereospecific methylation on Evans' oxazolidinone moiety was reported. According to the 13 C NMR analysis of this phosphine, the calix[4]arene skeleton adopted a 1,3-alternate conformation. The latter conformation of the macrocycle and the ( S )-chirality of the carbon atom bearing the methyl substituent were confirmed by a single-crystal X-ray diffraction study. After coordination of the phosphinated ligand to the dimeric [RuCl 2 ( p -cymene)] 2 organometallic precursor, the resulting arene-ruthenium complex was tested in the asymmetric reduction of acetophenone and alcohol was obtained with modest enantiomeric excess.