Chiral ferrocenyl ligands with pyridine nitrogen donors

Our long standing interest in chiral pyridine ligands, has lead us to undertake the synthesis of ligands with a stereogenic plane featuring a pyridine ring supported onto a ferrocene backbone. More recently we employed the same procedures for the synthesis of chiral ferrocenyl bipyridine and ferrocenyl pincer ligands.The key intermediate for the synthesis of targeted ligands, 2-Amino ferrocenyl carbaldehyde was synthesized in enantiopure form in 6-step from formylferrocene. The planar chirality was submitted using the chiral ortho-directing metalation.By Friedlander condensation with a suitable methyl ketone, 2-Amino ferrocenyl carbaldehyde was readily converted into the targeted pyridoferrocenyl ligands.The scope of these ligands in asymmetric catalysis was explored in the Pd-catalyzed allylic alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate. The conversion and enantioselectivity were highly dependent on the conditions of reaction. The best ee’s have been scored in chloroform at low temperature with lithium acetate as a base and thus far are not higher than 80%.