Synthesis of α,α-Diaryl-α-amino Acid Precursors by Reaction of Isocyanoacetate Esters with -Quinone Diimides.

A novel procedure for the synthesis of α,α-diaryl-α-amino acid derivatives has been developed. Silver oxide catalyzes the conjugate addition of α-aryl isocyanoacetates to -quinone diimide, affording the corresponding α,α-diarylisocyano esters in excellent yields and regioselectivities in short reaction times. Acid hydrolysis of the isocyano group provides the corresponding amino acids bearing a diarylated tetrasubstituted carbon atom. The reaction is also amenable to the synthesis of α-alkyl-α-arylisocyano esters, while the reaction with 3-hydroxy -quinone diimides provides 4-benzo[][1,3]oxazines via a conjugate addition/cyclization process.