Tandem Oxidation-Dehydrogenation of (Hetero)Arylated Primary Alcohols via Perruthenate Catalysis.

Tandem oxidative-dehydrogenation of primary alcohols to give α,β-unsaturated aldehydes in one pot are rare transformations in organic synthesis, with only two methods currently available. Reported herein is a novel method using the bench-stable salt methyltriphenylphosphonium perruthenate (MTP3), and a new co-oxidant NEMO·PF₆ (NEMO = N -ethyl- N -hydroxymorpholinium) which provides unsaturated aldehydes in low to moderate yields. The Ley-Griffith oxidation of (hetero)arylated primary alcohols with N -oxide co-oxidants NMO (NMO = N -methylmorpholine N -oxide)/NEMO, is expanded by addition of the N -oxide salt NEMO·PF₆ to convert the intermediate saturated aldehyde into its unsaturated counterpart. The discovery, method development, reaction scope, and associated challenges of this method are highlighted. The conceptual value of late-stage dehydrogenation in natural product synthesis is demonstrated via the synthesis of a polyene scaffold related to auxarconjugatin B. A novel method is described, using perruthenate salts, for performing the rarely reported dehydrogenation of primary alcohols to afford unsaturated aldehydes in low to moderate yields. The discovery, method development, reaction scope, and associated challenges of this method are presented in detail. [ABSTRACT FROM AUTHOR]