A Base and Solvent-Free Ruthenium-Catalyzed Alkylation of Amines

A (pyridyl)­phosphine-ligated
ruthenium­(II) catalyst is reported
for the chemoselective benzylic N-alkylation of amines, via a hydrogen-borrowing
mechanism. The catalyst operates under mild conditions, neat, and
without a base or other additive. These conditions offer remarkable
functional group compatibility for applications in organic synthesis,
including reactions involving phenols and anilines, which are very
difficult to achieve. Mechanistic studies suggest that, unlike other
catalysts for this reaction, the redox steps are fast and reversible
while imine formation is slow. We perceive that this is the origin
of the selectivity realized with these reaction conditions.

一种（吡啶基）膦配位的钌(II)催化剂被报道，用于胺的化学选择性苄基N-烷基化反应，该反应通过氢转移机制进行。该催化剂在温和条件下，无需添加剂或碱即可进行反应。这些条件为有机合成中的应用提供了显著的官能团相容性，包括涉及酚类和苯胺的反应，这些反应难以实现。机理研究表明，与该反应的其他催化剂不同，氧化还原步骤快速且可逆，而亚胺的形成则较慢。我们认为，这正是这些反应条件下实现的特异性的起源。