Triazole-phosphine Pd(II)-Enabled Dehydrogenation of Alcohols or Amines: A Combination of Experimental and Theoretical Study

We describe a novel triazole-phosphine Pd(II) (TPP) complex-catalyzed dehydrogenation reaction of alcohols or amines by using iodobenzene as the oxidant, in which a unique butterfly TPP dimer is first prepared via a three-component reaction of 1,2,3-triazole, P(Cy)3, and PdCl2 and the competitive cross-coupling reaction of iodobenzene with alcohols or amines could be avoided under TPP catalysis. In particular, the primary alcohols and imines can be further oxidized into acids or nitriles in a tunable manner, respectively. Preliminary mechanistic results by density functional theory calculation suggest that this reaction follows the Pd(II)–Pd(IV) catalytic pathway and the process of TPP-catalyzed oxidation dehydrogenation of alcohol or amine to form unsaturated bonds and Pd(II)–H species generated before the oxidative addition of TPP with iodobenzene, thereby avoiding competitive cross-coupling.