1,3-Dipolar cycloadditions catalyzed by bis(oxazoline)-magnesium-based chiral complexes. The importance of a Mg(II) counterion

✍ Scribed by Giovanni Desimoni; Giuseppe Faita; Annalisa Mortoni; PierPaolo Righetti

• Book ID: 104260899
• Publisher: Elsevier Science
• Year: 1999
• Tongue: French
• Weight: 235 KB
• Volume: 40
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(99)00101-x

✦ Synopsis

The 1,3-dipolar cycloaddition between N-acryloyl-oxazolidinone and diphenyl nitrone is catalyzed by chiral catalysts derived from bis(oxazoline) (R)-7 and Mg(II) perchlorate or triflate. In addition to complete regioselectivity, the endo cycloadduct can be obtained with up to 86% ee. The stereochemical results are due either to the specific counterion or to the presence of molecular sieves (as well as to the relative reagent concentrations). As a consequence, the enantioselecvity is opposite to that induced by the catalyst derived from Mg(II) iodide with the same chiral ligand.