Powerful Ti-Crossed Claisen Condensation between Ketene Silyl Acetals or Thioacetals and Acid Chlorides or Acids
Akira Iida, Syogo Nakazawa, Tomohito Okabayashi, Atsushi Horii, Tomonori Misaki and Yoo Tanabe*
*Department of Chemistry, School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337, Japan, Email: tanabekwansei.ac.jp
A. Iida, S. Nakazawa, T. Okabayashi, A. Horii, T. Misaki, Y. Tanabe, Org. Lett., 2006, 8, 5215-5218.
A Ti-crossed Claisen condensation between ketene silyl (thio)acetals and acid chlorides gave α-monoalkylated (thio)esters and thermodynamically unfavorable α,α-dialkylated β-keto (thio)esters in good yield. Addition of N-methylimidazole enhances the reactivity of less reactive ketene silyl acetals. The protocol was extended to the direct condensation of ketene silyl acetals with carboxylic acids.
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A. Iida, J. Osada, R. Nagase, T. Misaki, Y. Tanabe, Org. Lett., 2007, 9, 1859-1862.