Regiospecific and Stereoselective Alkylation of Allylic Substrates on Pd, Ir, and Rh Complexes with Chiral Phosphite Ligands

摘要

Substitution reactions in allylic systems by different nucleophiles catalyzed by transition metal complexes have been widely used in recent years in organic synthesis, including asymmetric synthesis. Asymmetrically substituted allylic systems are the most general and important in synthetic practice. The substitution in allylic substrates containing, along with a leaving group, only one substituent at one of the terminal carbon atoms of the allylic system may be accompanied by allylic rearrangement to give, in the general case, a mixture of two products: linear and branched. The branched product contains an asymmetric center and, therefore, can exist as two enantiomers. When complexes with chiral ligands are used as catalysts, the regio- and stereoisomeric composition of the reaction products depends on the nature of both the chiral ligand and the transition metal. In recent years, in addition to palladium catalysis, catalysis by Rh, Ir, and other metals has been often used in allylation reactions. The search for new types of chiral ligands, especially phosphite ones, is taking place in parallel. Therefore, it is an important problem to reveal factors affecting the regio- and stereoselectivity of allylation reactions.