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Abstract: A one pot synthesis of the 3,3-dimethylacroyl enol ester function found in the vibsane type diterpenes has been developed based on the Anders–Gaßner variant of the Wittig reaction (AGW reaction). This method uses easily accessible acyloxyalkylidene phosphoranes and a variety of aldehydes. [Copyright &y& Elsevier]

N,N,N′,N′-Tetramethylethylenediamine dioxide (TMEDAO2) was explored as a more atom economical co-oxidant for the Ley–Griffith oxidation of alcohols to aldehydes. TMEDAO2 was found to selectivity oxidise benzylic and allylic alcohols in comparable yields to that of the standard Ley–Griffith co-oxidant (NMO). Importantly TMEDAO2 facilitated tandem Ley–Griffith-Wittig reactions with stabilised ylides, in good to excellent yields, without the requirement of anhydrous conditions. [ABSTRACT FROM AUTHOR]

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]

A wide variety of novel non-hygroscopic N-oxide tetraphenylborate salts were synthesized and evaluated as co-oxidants in the Ley-Griffith (TPAP) oxidation of benzylic and allylic alcohols under non-anhydrous conditions. The novel DABCOO ·TPB (2:1) salt was herein unearthed as a viable competitor to the first-generation NMO ·TPB (2:1) salt, but more importantly gave increased performance under oxidative competition. X-ray crystal structure analysis and NMR spectroscopy revealed that depending on the crystallization conditions 1:1, 2:1 or 3:2 N-oxide-tetraphenylborate salts could be formed. [ABSTRACT FROM AUTHOR]