Nickel-catalyzed intramolecular homoallylation of omega-dienyl aldehyde

[GRAPHICS] In the presence of a catalytic amount of Ni(acac)(2), E3B and Et2Zn nicely promote a reductive homoallylic cyclization of omega -dienyl aldehydes and provide 2-allylcyclopentanols and -cyclohexanols with high stereoselectivit y in excellent yield, The reaction requires only two kinds of commercially available, inexpensive reagents, Ni(acac)(2) and Et2Zn or Et3B, and complet es at room temperature within 30 min with Et2Zn and 1-2 days with Et3B. No ligand additives (e.g., phosphine, nitrogen compounds) are required.