A practical synthetic approach to chiral α-aryl substituted ethylphosphonates

A convenient general method is reported for the synthesis of alpha -aryl substituted ethylphosphonic acids and esters by hydrogenation of alpha -aryl substituted ethenylphosphonic acids and esters. Racemic alpha -arylethylphosphonic acids and esters were prepared in 70-88%, yield under palladium-assisted transfer hydrogenation conditions using ammonium formate. Asymmetric hydrogenation of alpha -arylethenylphosphonic acids using chiral Ru(II) catalysts led to alpha -arylethylphosphonic acids with enantiomeric excesses up to 86%. (C) 2001 Elsevier Science Ltd. All rights reserved.