Ynolates were found to react with alpha-alkoxy-, alpha-siloxy-, and alpha-aryloxyketones at room temperature to afford tetrasubstituted olefins with high Z selectivity. Since the geometrical selectivity was determined in the ring opening of the beta-lactone enolate intermediates, the torquoselectivity was controlled by the ethereal oxygen atoms. From experimental and theoretical studies, the high Z
Ynolates react with ketones at room temperature to afford α,β,β-trisubstituted acrylates (tetrasubstituted olefins) with 2:1−8:1 geometrical selectivities. This can be regarded as a new olefination reaction of ketones giving tetrasubstituted olefins in good yield, even in the case of sterically hindered substrates. The reaction mechanism involves cycloaddition of ynolates with a carbonyl group and
A synthesis of multisubstituted vinylsilanes via ynolates: stereoselective formation of β-silyl-β-lactones followed by decarboxylation
作者:Mitsuru Shindo、Kenji Matsumoto、Kozo Shishido
DOI:10.1039/b418310j
日期:——
(Z)-Selective synthesis of multisubstituted vinylsilanes was achieved by stereoselective protonation or alkylation of beta-silyl-beta-lactone enolates, prepared by cycloadditions of acylsilanes with ynolates, followed by decarboxylation.
Asymmetric inverse electron-demand 1,3-dipolar cycloaddition of ynolates with chiral nitrones produced 5-isoxazolidinones with good diastereoselectivity. These products were easily converted into optically pure β-amino acids and chiral γ-butyrolactones.
Reductive lithiation of α,α-dibromo esters using lithium naphthalenide afforded ester dianions leading to ynolateanions in good yields. Naphthalene-catalyzed reductive lithiation was also accomplished. This is a convenient, economical and practical method for the preparation of ynolateanions.