Cyclopalladated aldehyde

Similar metal-mediated routes to indenols and indenones have been reported by other groups. A cyclopalladated aldehyde 75 gives indenones 76 stoichiometrically and the related indenols catalytically in the presence of stoichiometric amounts of the corresponding organomer-... 

This reaction seems to involve coordination of the phenolate oxygen to aryl-palladium intermediate and the successive cyclopalladation as the key steps. This is similar to the arylation of biphenyl-2-ols in Eqs. (56) and (57). A similar intramolecular reaction of haloaryl-linked aldehydes to give cyclic ketones is found in Eq. (20). This occurs along with a-arylation. 

There have been several reports of ortho-acylations using palladium catalysis. Orthoacylation of acetanilides with aldehydes is catalysed by palladium trifluoroacetate in the presence of f-butylhydroperoxide. A likely pathway involves the formation of a cyclopalladated intermediate (57), which reacts with an acyl radical to give (58) followed by carbon—carbon bond formation through reductive elimination. A similar methodology has been used in the preparation of a range of ort/io-acylacetanilides. ... 

Cyclometallation is a powerful tool for regiospecific substitution in functionalized aromatics, and a series of cyclopalladated t-butylimines of aromatic aldehydes react with styrene to give o-formylstilbenes in high yield. ... 

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