(–)-Sparteine-mediated stereoselective directed ortho metalation of ferrocene diamides

Abstract

The utility of (–)-sparteine-mediated directed ortho metalation (DoM) has been investigated in stereoselective preparation of planar chiral ferrocenes derived from 1,1′-N,N,N′,N′-tetraisopropylferrocenedicarboxamide (5). In the synthesis of C2-symmetric analogs of 5, the protocol (base, solvent, and two-step DoM) was found to be crucial for obtaining high enantio- and diastereo-selectivities of the products. A variety of highly enantioenriched mono and doubly functionalized derivatives of 5 have been synthesized. The synthetic applications of these compounds as chiral ligands in asymmetric alkylation of aldehydes and asymmetric palladium-catalyzed allylic substitutions have been demonstrated.Key words: directed ortho metalation, stereoselective deprotonation, ferrocene ligands, asymmetric catalysis.