Tiglic acid allylic oxidation

This oxidation is applicable to a wide variety of both electron-rich and electron-poor alkenes for example a number of tiglic acid derivatives undergo this reaction in moderate to excellent yield, as in equation (5). In cases where there are several nonequivalent allylic sites the course of this reaction is highly substrate dependent, and the yields and selectivity vary from excellent to mediocre. In tiisub-stituted alkenes (except fw most 1-al cyclohexenes), a reactivity pattern has emm ged which has been termed a preference for syn ene attack (or PSEA ) This means that O2 will preferentially attack one of the two allylic carbons which ate cu to each othw. In practical terms, this still translates into relatively low product selectivity in most cases such as in equation (6), although some notable excqrtions are known (equations 7 and 8). 

---