Lanthanide-PyBox complex

By taking advantage of the (salen)AlCl complex s ability to activate imide and of the lanthanide-PyBOX complex s ability to activate cyanide, intermolecular heterobimetallic dual cooperative catalysis was investigated. The dual catalyst system, that is, the combination of bench-stable (S,S)-[(salen)Al]20 complex and (S,S)-ErCl3-PyBOX complex, afforded distinctly superior results compared with (salen)AlCl complex alone (Table 13.33) [105]. Reaction times (from 26-48 to 8-14 hours), the amount of TMSCN (from 2.5-4 equiv to 2 equiv), and total catalyst loading (f rom 10 to 15 mol% to 7 mol%) decreased significantly. Reaction proceeded... 

Chapter 12 of this book. In some of these studies, lanthanide-PyBOX complexes are also examined, but Sc gave the best results. 

Scheme 17.24) [91]. Use of the corresponding lanthanide-PyBox complexes including gadolinium complex 171 enabled the cycloaddition of qui-nones (cf. 169) to give cycloadducts in superb optical purity (Equation 19) [92]. 

A comparative study on the influence of different lanthanide cations and the substituents at the 4 and 5 -positions in the pybox ligands in the Diels-Alder reaction of cyclopentadiene with 3-acryloyl-l,3-oxazolidin-2-one was realized [135], Of the catalysts derived from (4 P,5 P)-4-Me-5-Ph-pybox, the Sc(III)-based one is both strongly endo selective (endo/exo = 97/3) and highly enantioselective (97% ee (endo)). Later, it was found that the scandium-(4 S,5 S)-4-CH20TIPS-5-Ph-pybox complex also gave endo selective (endo/exo = 92/8-96/4) and highly enantioselective (93-99% ee (endo)) for the Diels-Alder reactions of cyclopentadiene with 3-acryloyl-or 3-crotonoyloxazolidinones. 

Schaus, S. E. Jacobsen, E. N. (2000) Asymmetric ring opening of meso- epoxides with TMSCN catalyzed by (pybox)lanthanide complexes., Org. Lett, 2 1001-1004. 

---