One-Pot Catalytic Synthesis of α-Tetrasubstituted Amino Acid Derivatives via In Situ Generation of N-Unsubstituted Ketimines.

A one-pot catalytic synthesis of α-tetrasubstituted amino acid derivatives via in situ generation of N-unsubstituted ketimines is reported. Because of the irreversible formation of N-unsubstituted ketimines, the yields were higher than those generated under the conventional one-pot reaction conditions. This process prevents the need to isolate unstable N-unsubstituted ketimines with alkyl substituents and streamlines the synthesis of highly congested α-amino acid derivatives.

Scandium(III) Triflate Catalyzed Direct Synthesis of N-Unprotected Ketimines.

N-Unprotected ketimines are useful substrates and intermediates for synthesizing valuable nitrogen-containing compounds, but their potential applicability is limited by the available synthetic methods. To address this issue, we report a scandium(III) triflate catalyzed direct synthesis of N-unprotected ketimines. Using commercially available reagents and Lewis acid catalysts, ketones were directly transformed into the corresponding N-unprotected ketimines in high yields with broad functional group tolerance, even in multigram scales. The reactions were readily applicable for one-pot synthesis of important compounds such as a glycine Schiff base without isolation of N-unprotected ketimine intermediates. Preliminary mechanistic studies to clarify the reaction mechanism are also described.