Copper(I)-Catalyzed Substitution Reactions of Propargylic Amines: Importance of C(sp)-C(sp3) Bond Cleavage in Generation of Iminium Intermediates

Substitution reactions of propargylic amines proceed in the presence of copper(I) catalysts. Mechanistic studies showed that C(sp)-C(sp(3)) bond cleavage assisted by nitrogen lone-pair electrons is essential for the reaction, and the resulting iminium intermediates undergo amine exchange, aldehyde exchange, and alkyne addition reactions. Because iminium intermediates are key to aldehyde-alkyne-amine (A(3)) coupling reactions, this transformation is effective not only for reconstruction of propargylic amines but also for chiral induction of racemic compounds in the presence of chiral catalysts.