Phthalimides, reaction with epoxides

Another method for the conversion of an alkene into an allylic alcohol, but with a shift in the position of the double bond, proceeds from the corresponding p-hydroxyselenide. The p-hydroxyselenide can be obtained from the epoxide by reaction with phenylselenide anion or directly from the alkene by addition of phenylselenenic acid, phenylselenenyl chloride in aqueous MeCN, or by acid-catalysed reaction with A-phenylseleno-phthalimide. The hydroxyselenide does not need to be isolated, but can be oxidized directly with tert-BuOOH to the unstable selenoxide, which spontaneously eliminates phenylselenenic acid to form the E-allylic alcohol. For example, 4-octene gave 5-octen -ol (6.15). Elimination takes place away from the hydroxy group to give the allylic alcohol no more than traces... 

Electrophilic agents other than halide can be used in reactions with phthalimide. One example involved opening the epoxide moiety in 1.47 with phthalimide, catalyzed by palladium (0), to give methyl 4-(N-phthalimido)-5-hydroxyhex-2-enoale, 1.48. This example is also an example of the powerful palladium (0) chemistry that has been applied to many systems over the last few years. 

Vinyl epoxides can also be used as substrates for formation of optically active allyl amines catalyzed by the same type of chiral palladium complexes as in Eq. (10). By reaction of simple vinyl epoxides with phthalimide as the nitrogen source in the presence of the chiral palladium complexes as the catalyst, very high ee (> 98 %) and regioselectivity (> 97 %) were obtained [26]. A variety of different applications of the use of the palladium-catalyzed approach for the formation of allyl amines and the use of this in total synthesis has been pursued by several research groups, and further details can be obtained in a review by Trost et al. [19d]. 

The reaction of 2-pyrimidone with vinyl epoxide 16 also takes place under neutral conditions, as oxidative addition of 16 to palladium(O) generates an alkoxide that is sufficiently basic to deprotonate 2-pyrimidone22. In contrast, allyl ester (lS,4/ )-18 demands the use of the potassium phthalimide salt for C-N bond formation33. Similar to the purine /V-allylations with 16 and 18, only the depicted isomers 26 and (15,4f )-27 result. Potassium phthalimide thus represents another ammonia equivalent in palladium(0)-catalyzed allylic substitutions66. 

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