Oxidative cleavage, degradation rearrangement

Serajuddin et al. [19] reported that the degradation pathway of prevastatin sodium was directly linked to the micro-pH environment within the formulation. Under neutral conditions (pH 6.5), the statin formed two degradation products, a cyclic lactone and an internal hydroxyl rearrangement product. However, as the pH was increased to 9.9 with the incorporation of magnesium oxide into the blend, the only degradation mechanism involved the formation of the cleavage product, 2-methylpropanoic acid. This latter approach of increasing the... 

Figure 69 depicts the degradants and the proposed degradation pathway involving (1) rearrangement to isotimolol, (2) ether cleavage to form 4-hydroxy-3-morpholino-l,2,5-thiadiazole, and (3) oxidation followed by ether cleavage to form 4-hydroxy-3-morpholino-l,2,5-thiadiazole-l-oxide (109). 

Azides are utilized for various C-C cleavage reactions [45]. For example, the alkylarene 78 v ras converted to the aniline 81 upon treatment with n-nonyl azide and an iron catalyst under oxidative reaction conditions (Scheme 7.30). Oxidation of the arene 78 generates the benzyhc cation 79, which reacts with the azide. Subsequent Schmidt rearrangement generates the iminium cation 80, which hydrolyzes to form the aniline 81. This method was applicable to degradation of low molecular weight polystyrenes to arylamines [45c]. 

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