Decarboxylative Cyclizations and Cycloadditions of Palladium-polarized Aza-ortho-Xylylenes.

Previously we have shown that palladium catalysts effect the decarboxylation of vinyl oxazinones to form zwitterionic π-allyl palladium intermediates (A, Scheme 1).1 Thus, vinyl oxazinones can be equated with zwitterionic synthons (B). In the absence of other electrophiles, the zwitterionic intermediate cyclizes to form vinyl azetidines with high diastereoselectivity. Moreover, in the presence of suitably electrophilic Michael acceptors,2 the intermediates undergo diastereoselective cycloadditions to generate highly substituted piperidine derivatives. 3