Optically Pure Calixarenyl Phosphine via Stereospecific Alkylation on Evans’ Oxazolidinone Moiety
2024
Claude Bauder | David Sémeril
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&rsquo: oxazolidinone moiety was reported. According to the 13C 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 [RuCl2(p-cymene)]2 organometallic precursor, the resulting arene&ndash:ruthenium complex was tested in the asymmetric reduction of acetophenone and alcohol was obtained with modest enantiomeric excess.
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