Ley oxidation

The mechanism of the Ley oxidation is complex and the exact nature of the species involved in the catalytic cycle is unknown. The difficulty in establishing an exact mechanism arises from the fact that the complexes of Ru ", Ru ", Ru , Ru and Ru are all capable of stoichiometrically oxidizing alcohols to carbonyl compounds. The TRAP reagent can oxidize alcohols stoichiometrically as a three-electron oxidant and can also be used as a catalyst when a co-oxidant is present (e.g., NMO, TMAO, or hydroperoxides). Data suggests that the oxidation proceeds via the formation of a complex between the alcohol and TRAP (ruthenate ester). It was also found that the stoichiometric oxidation of isopropyl alcohol with TRAP is autocatalytic and the catalyst is suspected to be colloidal RUO2. Small amounts of water decrease the degree of autocatalysis. This observation is supported by the finding that the addition of molecular sieves improves the efficiency of the reaction. 

The total synthesis of the immunosuppressant (-)-pironetin (PA48153C) was accomplished by G.E. Keck and co-workers. The six-membered a,(3-unsaturated lactone moiety was installed using a lactone annulation reaction by reacting the advanced aldehyde intermediate with the lithium enolate of methyl acetate. The aldehyde was prepared by the Ley oxidation of the corresponding primary alcohol and was used without purification in the subsequent annulation step. 

In the laboratory of D. Tanner, a novel method was developed for the stereoselective synthesis of ( )-tributylstannyl-a,P-unsaturated ketones in two steps from secondary propargylic alcohols. The first step was the highly regio- and stereoselective Pd-catalyzed hydrostannylation of the triple bond followed by a mild Ley oxidation. This method was utilized for the construction of a key intermediate for the total synthesis of zoanthamine. 

During the total synthesis of (-)-motuporin by J.S. Panek et al., the modified Ley oxidation was utilized in the preparation of the key A/-Boc-valine-Adda fragment. In order to obtain the carboxylic acid, the TPAP and NMO were administered twice, and the second portion of TPAP/NMO was accompanied by the addition of water. The water formed aldehyde hydrate which was oxidized to the carboxylic acid. The oxidation is so mild that the labile a-stereocenter was left intact. 

The first total synthesis of the marine dolabellane diterpene (+)-deoxyneodolabelline was achieved in the laboratory of D.R. WilliamsJ In the final step of the synthetic sequence, the oxidation of a secondary alcohol functionality of a 1,2-diol to the corresponding a-hydroxy ketone was required. Such 1,2-diols are known to be unstable under most oxidation conditions, and often glycol cleavage is observed. Indeed, when Dess-Martin and Ley oxidations were tried, the substrate suffered carbon-carbon bond cleavage. However, under the Swern oxidation conditions, the desired a-hydroxy ketone was isolated in a 65% yield. Interestingly, the substrate was a mixture of four inseparable diastereomeric diols (obtained in a McMurry reaction), which gave two easily separable ketone products, one of which was the natural product. 

Ley oxidation Oxidation of primary and secondary alcohols with TPAP/NMO to give the corresponding aldehydes and ketones. 260... 

Related reactions Dess-Martin oxidation, Jones oxidation, Ley oxidation, Oppenauer oxidation, PTitzner-Moffatt oxidation, Swern oxidation ... 

F.i. Tetrapropylammonium Perruthenate-Ley Oxidation. Ruthenium derivatives have been used for oxidation reactions. A particularly useful one is TPAP, introduced by Ley for the oxidation of alcohols and called Ley oxidation. 1 2 a very mild oxidizing agent that is compatible with many sensitive... 

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