Clean osmium-catalyzed asymmetric dihydroxylation of olefins in ionic liquids and supercritical CO2 product recovery

Abstract

The combination of ionic liquids (ILs) as solvents in the asymmetric Sharpless dihydroxylation (AD) with the use of scCO(2) in the separation process allows a very simple, efficient, clean and robust system for the reuse of the AD catalytic system, which also does not need the use of organic solvents either for the reaction or for the separation of products and allows the isolation of the diol, in high yield and enantiomeric excess and basically without contamination with osmium.

Osmium catalyzed asymmetric dihydroxylation of methyl trans-cinnamate in ionic liquids, followed by supercritical CO2 product recovery

“…The model substrate in these studies was 1-hexene. In this work, we performed a series of experiments of AD were selected as potential candidates for further experiments, on the basis of previous study of the AD reaction in ILs for a range of aryl and alkyl-olefins [21].…”

“…In line with our ongoing interest in the development of new ILs [30], their application in separation technology [27c,31], and their use as an efficient reaction medium for catalyst immobilization [19a,c,32], and encouraged by the results obtained for the AD reaction on the model substrate 1-hexene [21], we applied this methodology to the important substrate methyl transcinnamate 1. The importance of this substrate lies in the fact that it allows for the preparation of the diol 2, a known efficient precursor for the synthesis of the taxol side chain 3 (Scheme 1).…”

“…Moreover, extensive research of osmium catalyst immobilization in ionic liquids only, without any other reaction solvents, followed by supercritical CO 2 extraction, has been conducted in our laboratories [21].…”

Asymmetric Catalytic Synthesis of Organic Compounds using Metal Complexes in Supercritical Fluids

“…This reaction has been performed on methyl E-cinnamic acid esters in ionic liquids, with the product recovery involving extraction with scCO 2 . [42,43] 6 giving the best results (88 % yield, < 0.05 % Os). The reaction and extraction were repeated 6 times, with addition of fresh substrate and oxidant each time.…”

Ionic Liquids as Solvents for Catalyzed Oxidations of Organic Compounds

“…[84] Subsequently, the same team has also studied their K 2 OsO 2 (OH) 4 -L* catalytic sys- [86] Recently, with the team of Nunes da Ponte who has studied different mixtures of ILs under high pressures of CO 2 , [87] Afonso et al have shown the efficiency of the use of scCO 2 in the separation process, allowing a better recyclability of the catalyst/IL system. [88] As for Songs team, it observed that the use of OsO 4 with (DHQ) 2 (57)]. [85] These asymmetric dihydroxylation processes, in particular the effect of the ligand structure on recyclability, have subsequently been studied by Sheldon et al [89] ð57Þ S. Zhang et al have mono-quaternized Songs ligand to obtain (QN þ )(QN)PHAL (Scheme 18).…”