Hydrazine Hydrate Accelerates Neocuproine–Copper Complex Generation and Utilization in Alkyne Reduction, a Significant Supplement Method for Catalytic Hydrogenation

Diimine
(HNNH) is a strong reducing agent, but the efficiency
of diimine oxidized from hydrazine hydrate or its derivatives is still
not good enough. Herein, we report an in situ neocuproine–copper
complex formation method. The redox potential of this complex enable
it can serve as an ideal redox catalyst in the synthesis of diimine
by oxidation of hydrazine hydrate, and we successfully applied this
technique in the reduction of alkynes. This reduction method displays
a broad functional group tolerance and substrate adaptability as well
as the advantages of safety and high efficiency. Especially, nitro,
benzyl, boc, and sulfur containing alkynes can be reduced to the corresponding
alkanes directly, which provides a useful complementary method to
traditional catalytic hydrogenation. Besides, we applied this method
in the preparation of the Alzheimer’s disease drug CT-1812
and studied the mechanism.