The first catalytic asymmetric homo-aldol reaction of ethyl
pyruvate leading to diethyl-2-hydroxy-2-methyl-4-oxoglutarate in up to 96%
enantiomeric excess is reported; this reaction has been investigated for
various catalysts, amines and solvents, and it is demonstrated that this
new reaction leads to a simple synthetic procedure for the formation of
optically active isotetronic acid derivatives.
text] L-proline failed to act as an organocatalyst in the homoaldol reaction of ethyl pyruvate; however, it reacted with the ester to give an azomethine ylide that in turn underwent 1,3-dipolar cycloaddition with a second molecule of pyruvate. Direct catalytic homoaldol reaction of ethyl pyruvate was performed using an (S)-(+)-1-(2-pyrrodinylmethyl)pyrrolidine/trifluoroacetic acid combination as organocatalyst