Selective deuteroreduction of alkynes by Zn/Mn with nickel catalysis under mechanical conditions

Abstract

Selective deuteroreduction of alkynes remains a longstanding challenge, as semi-deuteration is often hampered by overreduction, while tetra-deuteration suffers from incomplete conversion. Herein, we report a mechanochemically driven nickel-catalyzed deuteroreduction of alkynes, in which the mechanical activation of Zn and Mn modulates the selective formation of either semi-deuterated or tetra-deuterated products. Control experiments demonstrated that the selectivity is governed by the interplay between the distinct reducing abilities of Zn/Mn and the catalytic role of nickel. During the reaction, the low-valent nickel catalyst coordinates with the semi-deuterated alkene intermediate; the stronger reducing ability of Mn then activates this intermediate, enabling further conversion to the tetra-deuterated product. This protocol is applicable to the selective deuteroreduction of terminal and internal alkynes, affording deuterated compounds with high efficiency and excellent isotopic purity.