4‐Aminothiourea Prolinol <i>tert</i>‐Butyldiphenylsilyl Ether: A Chiral Secondary Amine‐Thiourea as Organocatalyst for Enantioselective <i>anti</i>‐Mannich Reactions

Abstract

Abstract anti ‐Selective Mannich reactions of N ‐ p ‐methoxyphenyl (PMP)‐protected α‐iminoglyoxylate with unmodified aldehydes or ketones were effectively catalyzed by 4‐aminothiourea prolinol tert ‐butyldiphenylsilyl ether. The reactions led to chiral β‐amino carbonyl compounds in high yields (up to 94%), excellent diastereo‐ and enantioselectivities (up to 98% de and &gt;99% ee ). The study demonstrated for the first time that direct Mannich‐type reactions of unmodified aldehydes or ketones to α‐iminoglyoxylate can be promoted by secondary amine‐thiourea chiral organocatalyst.