Hemilability Driven Water Activation: A Ni(II) Catalyst for Base-Free Hydration of Nitriles to Amides.

Hemilability Driven Water Activation: A Ni(II) Catalyst for Base-Free Hydration of Nitriles to Amides. Chemistry. 2017 Apr 07;: Authors: Bera JK, Singh K, Sarbajna A, Dutta I, Pandey P Abstract A Ni(II) complex 1 containing pyridyl- and hydroxy-functionalized N-heterocyclic carbenes (NHC) is synthesized and its catalytic utility for selective nitrile hydration to amide under base-free condition is evaluated. The title compound exploits hemilabile pyridyl unit to interact with a catalytically relevant water molecule via hydrogen-bonding and promote nucleophilic water attack to the nitrile. A wide variety of nitriles are hydrated to the corresponding amides including pharmaceutical drugs Rufinamide, Rifater and Piracetam. Synthetically challenging α-hydroxyamides are accessed from cyanohydrins under neutral conditions. Related catalysts that lack the pyridyl unit (2 and 4) are not active whereas those containing both the pyridyl and the hydroxy or only the pyridyl pendant (1 and 3) show substantial activity. A linkage isomer 1' where hydroxy group is bound to the metal instead of the pyridyl was isolated under different crystallization conditions insinuating ligand hemilabile behavior. pKa measurements reveal accessible pyridyl unit under catalytic conditions. Kinetic studies support a ligand-promoted nucleophilic water addition to a metal-bound nitrile. This work reports a Ni based catalyst that exhibits functional hemilability for h...
Source: Chemistry - Category: Chemistry Authors: Tags: Chemistry Source Type: research