Baeyer-Villiger reaction buffers

More recently, permaleic acid has been recommended as a very satisfactory reagent for the Baeyer-Villiger reaction. It reacts almost as fast as trifluoroperoxyacetic acid and does not require buffering. Unfortunately, neither of these two reagents has been used extensively on 20-keto steroids a patent claims the conversion of progesterone to testosterone acetate with trifluoroperoxyacetic acid, but a later communication describes the ready reaction of 3-keto-A" -steroids with this reagent. 

Baeyer-Villiger reaction. This peracid has been used for the Baeycr-Villiger reaction with cyclopentanones and cyclohexanones. The reaction is carried out with 1.25 molar equiv. of benzeneseleninic acid and 10 molar equiv. of H2O2 in THF or CH2CI2 buffered to pH 7. Yields are comparable to those with other peracids. One example, 1 2, was reported where oxidation was achieved only with this peracid. 

In the Baeyer-Villiger reaction of 4-nonanone to butyl pentanoate with trif-luoroperoxyacetic acid, a large excess of sodium acetate is sometimes added as a buffer. Explain why this is necessary. 

The choice of the oxidant is primordial, as it acts both as the nucleophile and the leaving group. A reactivity order of oxidants has been established [174]. Peracids and especially m-CPBA [296] are the most efficient oxidants for the Baeyer-Villiger reaction, followed by alkyl peroxides. The reaction with peracids proceeds faster under acid catalysis [297], but buffered solutions can also be used. Some ketones are un-reactive under standard conditions, and need to be transformed into their hemiketals [298]. Safer peracids such as MMPP (magnesium monoperphthalate) [299, 300] and sodium perborate [301] have also been applied giving similar results as m-CPBA. Recently, processes with solid-supported peracids [302] and transformations in the solid state [303] have been developed. 

The peracid is prepared in 65-75% yield by the reaction between o-sulfobenzoic anhydride and 30 % hydrogen peroxide in acetone solution at - 4 to 0°C. The solution is used directly for epoxidation of olefins. Since the reagent contains a strongly acidic group, the initially formed epoxide undergoes acid cleavage to a trans-diol unless a solid buffer such as sodium carbonate is present. The peracid can also be used for Baeyer-Villiger oxidation and for oxidation of heterocyclic f-amines to N-oxides.1... 

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