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Zr[bis(salicylidene)ethylenediaminato]-mediated Baeyer-Villiger oxidation: stereospecific synthesis of abnormal and normal lactones.

ABSTRACT: Baeyer-Villiger oxidation of racemic bicyclic cyclobutanones with Zr[bis(salicylidene)ethylenediaminato] (salen) complex 1 as catalyst in the presence of a urea-hydrogen peroxide adduct was found to proceed enantiospecifically. The enantiotopos selection in the oxidation was governed primarily by the Zr(salen) catalyst, although migratory aptitude (methine > methylene > methyl) in Baeyer-Villiger oxidation affected the selection to a varied extent, depending on the substrate structures; one enantiomer of cyclobutanones gave exclusively a normal lactone expected from the migratory aptitude, and the other enantiomer gave an abnormal lactone preferentially, the formation of which is counter to the migratory aptitude. Furthermore, the rates of abnormal lactone formation were found to be faster than those of normal lactone formation in most of the oxidations examined. For example, the enantiomer of racemic bicyclo[3.2.0]heptan-6-one giving an abnormal lactone reacted 2.2 times faster than the other enantiomer giving a normal lactone. To our knowledge, this example of chemocatalytic Baeyer-Villiger oxidation giving an abnormal lactone in preference to a normal lactone has been previously unreported. This unusual behavior is likely to be attributable to strict control of stereoelectronic demand in Baeyer-Villiger oxidation and chiral recognition by complex 1.

SUBMITTER: Watanabe A

PROVIDER: S-EPMC395977 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Perdecanoic acid as a safe and stable medium-chain peracid for Baeyer-Villiger oxidation of cyclic ketones to lactones.

Project description:Stability studies dedicated to high-energy compounds for a series of linear peracids (C6-C12), including sensitivity to mechanical impulse (shock and friction), as well as electrical (spark) and thermal sensitivity (temperature and heat of decomposition), were presented in this work for the first time. Studies revealed that all peracids were insensitive to shock, while in the case of the other sensitivity tests sharp differences between results for C8 and C10 peracids were observed. Taking into account the relatively high initial temperature of decomposition (above 64 °C) perdecanoic acid was selected as a safe alternative to commonly used hazardous short-chain peracids. Next, a new method for the Baeyer-Villiger oxidation was presented. Oxidation of 2-adamantanone was chosen as a model reaction. Peroctanoic, perdecanoic and perdodecanoic acids were tested as oxidants. Peroctanoic acid was the most reactive but taking into account both safety and kinetic issues, perdecanoic acid was selected for the further studies. The influence of reaction conditions on reaction rate was investigated. Optimized reaction conditions were suggested (two-fold molar excess of peracid with respect to the ketone, toluene as a solvent, 35 °C). This exploratory study offers promise with regard to the development of safer alternatives to peracetic acid in industrial oxidation.

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A Synergistic Combinatorial and Chiroptical Study of Peptide Catalysts for Asymmetric Baeyer-Villiger Oxidation.

Project description:We report an approach to the asymmetric Baeyer-Villiger oxidation utilizing bioinformatics-inspired combinatorial screening for catalyst discovery. Scaled-up validation of our on-bead efforts with a circular dichroism-based assay of alcohols derived from the products of solution-phase reactions established the absolute configuration of lactone products; this assay proved equivalent to HPLC in its ability to evaluate catalyst performance, but was far superior in its speed of analysis. Further solution-phase screening of a focused library suggested a mode of asymmetric induction that draws distinct parallels with the mechanism of Baeyer-Villiger monooxygenases.

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