Synthesis of indenols and indanones via catalytic cyclic vinylpalladation of aromatic aldehydes

o-Bromobenzaldehyde 1, in the presence of a palladium catalyst, smoothly un derwent consecutive intermolecular carbopalladation with internal alkynes 2 and then intramolecular nucleophilic vinylpalladation of the aldehyde func tion to produce the indenol derivatives 4 in high yields. Further heating o f 4 under more elevated temperature caused complete isomerization to the co rresponding indanones 8. A mechanism for this nucleophilic vinylpalladation of aromatic aldehydes is proposed. (C) 1999 Elsevier Science Ltd. All righ ts reserved.