Enantioselective decarboxylative Mannich reaction of β-keto acids with -alkynyl -Boc ,-acetals: access to chiral β-keto propargylamines.

The chiral keto-substituted propargylamines are an essential class of multifunctional compounds in the field of organic and pharmaceutical synthesis and have attracted considerable attention, but the related synthetic approaches remain limited. Therefore, a concise and efficient method for the enantioselective synthesis of β-keto propargylamines chiral phosphoric acid-catalyzed asymmetric Mannich reaction between β-keto acids and -alkynyl -Boc ,-acetals as easily available -alkynyl imine precursors has been demonstrated here, affording a broad scope of β-keto -Boc-propargylamines in high yields (up to 97%) with generally high enantioselectivities (up to 97 : 3 er).