Stereoselective olefination of unfunctionalized ketones via ynolates.
Ynolates react with ketones at room temperature to afford alpha,beta,beta-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 subsequent thermal electrocyclic ring-opening of the resulting beta-lactone enolates. The stereoselectivity is determined in the ring-opening, which is regulated by torquoselectivity. In this paper, we describe the scope and limitations of olefination of ketones via ynolates and discuss the stereocontrol mechanism.
Shindo
Mitsuru
M
Institute for Medicinal Resources, University of Tokushima, Sho-machi 1, Tokushima 770-8505, Japan. shindo@ph.tokushima-u.ac.jp
Sato
Yusuke
Y
Yoshikawa
Takashi
T
Koretsune
Ryoko
R
Shishido
Kozo
K