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A non-hygroscopic tetraphenylborate salt of N-methylmorpholine- N-oxide (NMO) is reported (NMO ⋅TPB), which modulates the standard Ley-Griffith oxidation such that benzylic and allylic alcohols are oxidised selectively. An attractive feature of this new protocol is that anhydrous conditions are not required for this selective tetra- n-propylammonium perruthenate (TPAP) oxidation, superseding the requirement of molecular sieves. [ABSTRACT FROM AUTHOR]

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]

Abstract: The Ley–Griffith tetra‐n‐propylammonium perruthenate (TPAP) catalyst has been widely deployed by the synthesis community, mainly for the oxidation of alcohols to aldehydes and ketones, but also for a variety of other synthetic transformations (e.g. diol cleavage, isomerizations, imine formation and heterocyclic synthesis). Such popularity has been forged on broad reaction scope, functional group tolerance, mild conditions, and commercial catalyst supply. However, the mild instability of TPAP creates preparation, storage, and reaction reproducibility issues, due to unpreventable slow decomposition. In search of attributes conducive to catalyst longevity an extensive range of novel perruthenate salts were prepared. Subsequent evaluation unearthed a set of readily synthesized, bench stable, phosphonium perruthenates (ATP3 and MTP3) that mirror the reactivity of TPAP, but avoid storage decomposition issues. [ABSTRACT FROM AUTHOR]