Sc(OTf)(3)-catalyzed effcient synthesis of beta,beta-bis(indolyl) ketones by the double indolylation of acetic acid 2-methylene-3-oxobutyl ester

In the presence of 5 mol% Sc(OTf)(3), double indolylation of acetic acid 2-methylene-3-oxo-butyl ester with differently substituted indoles readily afforded β,β-bis(indolyl) ketones. The reaction may proceed via a Sc(OTf)(3)-catalyzed SN2'-type substitution and subsequent conjugate addition.