Superoxide ester cleavage

After drying this block polymer precursor, partial hydrolysis of the methacrylate block lead to the ion containing block copolymer. The hydrolysis route is shown in Scheme II. The hydrolysis method employed utilized potassium superoxide as a general route to ester cleavage to generate in a direct fashion potassium carboxylate units. 

The observation that R-2-octyl acetate yields R-2-octanol with 99% retention rules out the possibility that the reaction occurs by alkyl-oxygen fission [10]. This mechanism is consistent with the normal mode of ester hydrolysis which also occurs by acyl-oxygen fission. Neither amides nor nitriles were affected by superoxide under phase transfer conditions [10]. The data on ester cleavage by superoxide ion is summarized in Table 8.3. 

RC=N -+ RCONHz. Sodium superoxide in DMSO converts nitriles to amides (2-30 hours) in reasonable yields. The paper also reports cleavage of esters by NaOg in DMSO at 20° in 1-8 hours. ... 

Cleavage of esters. Esters, but not amides, are cleaved in high yield by potassium superoxide in the presence of 18-crown-6. This reaction is relevant to certain biological oxidations that apparently involve 02. ... 

SanFilippo, J., Jr., C.-I. Chern, and J. S. Valentine Oxidative Cleavage of a-Keto, a-Hydroxy- and a-Halo Ketones, Esters and Carboxylic Acids by Superoxide. J. Org. Chem. 41, 1077 (1976). 

Superoxide ion reacts with esters in the presence of 18-crown-6 affording the corresponding acids after aqueous work-up [7, 8, 10]. This reaction was first reported by Corey who found that cleavage occurred as well as displacement in ester mesylates and tosylates [7, 8]. Two examples of this reaction are shown in equations 8.6 and 8.7. 

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