ИСТИНА

Remarkable achievements in asymmetric catalysis with chiral palladacycles have given a powerful impetus to development of the routes to a more elaborate collection of cyclopalladated complexes (CPC's) of diverse structural and stereochemical types. This report describes recent results obtained by our group in the field of enantiomerically pure palladacycles with nitrogen, sulfur or phosphorus donor atoms that are derived from amines, imines, thioamides, phosphines, phosphites or phosphinites. Examples of the CPC's reported contain compounds of axial and planar chirality of metallocene or non-metallocene type, as well as complexes with stereogenic carbon, phosphorus or nitrogen atoms, including structures with a direct Pd-C* or Pd–P* bond. All these complexes may be considered as potential enantioselective (pre)catalysts or precatalysts. Several new strategies for preparation of enantiopure CPC's will be discussed. The most important method is asymmetric transcyclopalladation, based on the use of enantiopure CN-palladacycle as a chirality inductor in the C–H bond activation of P-donor ligand. Two versions of this approach were developed, designed for asymmetric cyclopalladation of prochiral and racemic ligands. Another new method is destined for racemic palladacycle resolution; it is based on diastereoselective decoordination of chiral auxiliary ligand on silica. Examples of CPC applications will also be presented. They include palladacycle using as chiral deivatizing reagents for enantiomer separation, enantiomeric composition determination and spectral estimation of absolute configuration of substrates, capable for palladium coordination. Two aspects of palladacycle using in asymmetric catalysis will be also presented: (i) they may be used as enantioselective (pre)catalysts, and (ii) as testing molecules for mechanistic studies of stoichiometric and catalytic processes.