Vinyl ethers diastereoselective oxidation reaction

In the presence of additional unsaturation, the intermediate a-palladium bond formed in these transformations can undergo a further Heck process to establish an additional C-C bond. The reactions of allylic alcohols with vinyl ethers proceed along this pathway and lead diastereoselectively to THFs (Equation (112)), with Cu(OAc)2409 and 02410 used as the stoichiometric oxidants. This methodology has been used to good effect in the syntheses of (—)-dihy-droxanthatin,409 fraxinellone limonoids,411 and mycalamide A.412... 

Beckwith has observed moderate diastereoselectivity in this reaction involving cyclic systems. The cyclizations of allyl and homoallyloxycarbonyloxy radicals are potentially useful as radical based alternatives for an overall oxidation or hydrolysis of a double bond, and also various further transformations of the cyclic carbonates can lead to synthetically useful products.62b In contrast, simple alkoxycarbonyloxy radicals 91a add intermolecularly to ethyl vinyl ether to give, ultimately, carbonates of glycoaldehyde derivatives 91b, Scheme 37.62a... 

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