Recyclable diguanidinium-BINAP and PEG-BINAP supported catalysts: syntheses and use in Rh(I) and Ru(II) asymmetric hydrogenation reactions

The syntheses of new recyclable cationic BINAP type ligand diguanidinium 1 and PEG-bound BINAP ligand 2 are described. The use of ethylene glycol instead of water increased the enantioselectivity in the ruthenium-promoted hydrogenation reaction of functionalized ketones. These catalysts are highly active (catalyst/substrate ratio up to 1:10 000, up to 99% e.e.). The rhodium-mediated hydrogenation of acetamidoacrylic acid was also examined using 1 and 3 as chiral auxiliaries.