# Optically Pure Calixarenyl Phosphine via Stereospecific Alkylation on Evans’ Oxazolidinone Moiety

## TL;DR

Scientists developed a new method to create a chiral phosphine compound using a calixarene structure, which was tested in a chemical reaction to produce an alcohol with some chirality.

## Contribution

A novel stereospecific synthesis of a chiral calixarenyl phosphine and its application in asymmetric catalysis.

## Key findings

- The calix[4]arene skeleton adopts a 1,3-alternate conformation confirmed by 13C NMR.
- The (S)-chirality of the compound was confirmed by single-crystal X-ray diffraction.
- The ruthenium complex showed modest enantiomeric excess in the asymmetric reduction of acetophenone.

## Abstract

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 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–ruthenium complex was tested in the asymmetric reduction of acetophenone and alcohol was obtained with modest enantiomeric excess.