Chiral cyclopropenimine-catalyzed enantioselective Michael reactions of phenol and benzofuran-derived α,β-unsaturated pyrazolamides with benzophenone-imine of glycine esters

The enantioselective Michael reactions of benzophenone-imine of glycine esters with phenol- and benzofuran-derived α,β-unsaturated pyrazolamides have been realized by using a chiral cyclopropenimine (Lambert catalyst, CSB-1 ) as an organocatalyst. In the presence of 20 mol % CSB-1 , the Michael adducts were obtained in up to 85% yield and 98% ee under mild conditions. The configurations of these Michael products were deduced by X-ray single crystal diffraction of a pyroglutamic acid ester containing two adjacent stereocenters, which was obtained from in-situ acidic hydrolysis and lactamization of the corresponding Michael product.