Organocatalytic Enantioselective Hydrazination of 1,3-Dicarbonyl ­Compounds: Asymmetric Synthesis of (alpha),(alpha)-Disubstituted (alpha)-Amino Acids

The organocatalytic (alpha)-hydrazination of ?-keto esters using a bifunctional urea as catalyst and azodicarboxylates as electrophiles has been investigated and is shown to proceed in high yields and with good enantioselectivity. The scope of the reaction is de­ monstrated for various substrates and the urea catalyst 1b was revealed to be superior to thiourea 1a. Furthermore, transformation of the obtained product 4aa into optically active amino acid derivative 10 is also presented.