Powerful Ti-crossed Claisen condensation between ketene silyl acetals or thioacetals and acid chlorides or acids.
[Structure: see text] A powerful Ti-crossed Claisen condensation between ketene silyl acetals (KSAs) and acid chlorides was successfully performed to give alpha-monoalkylated esters and thermodynamically unfavorable (less accessible) alpha,alpha-dialkylated beta-keto esters in good yield (46 examples; 41-98% yield). A closely related reaction between ketene silyl thioacetals (KSTAs) and acid chlorides also proceeded smoothly to give alpha-monoalkylated and alpha,alpha-dialkylated beta-keto thioesters (21 examples; 61-97% yield). The present protocol was extended to the direct condensation of KSAs with carboxylic acids (14 examples; 71-97% yield).
Iida
Akira
A
Department of Chemistry, School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337, Japan.
Nakazawa
Syogo
S
Okabayashi
Tomohito
T
Horii
Atsushi
A
Misaki
Tomonori
T
Tanabe
Yoo
Y