Heteroatom-guided torquoselective olefination of α-oxy and α-amino ketones via ynolates

Ynolates were found to react with α-alkoxy-, α-siloxy-, and α -aryloxyketones at room temperature to afford tetrasubstituted olefins with high Z selectivity. Since the geometrical selectivity was determined in the ring opening of the β-lactone enolate intermediates, the torquoselectivity was controlled by the ethereal oxygen atoms. From experimental and theoretical studies, the high Z selectivity is in duced by orbital and steric interactions rather than by chelation. In a similar manner, α-dialkylamino ketones provided olefins with excellent Z selectivity. These products can be easily converted into multisubstituted butenolides and γ-butyrolactams in good yield.