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).

NaOH-catalyzed crossed Claisen condensation between ketene silyl acetals and methyl esters.

We have developed a practical crossed Claisen condensation between ketene silyl acetals and methyl esters using catalytic NaOH to obtain alpha-monoalkylated beta-keto esters and inaccessible alpha,alpha-dialkylated beta-keto esters.

Practical and robust method for regio- and stereoselective preparation of (E)-ketene tert-butyl TMS acetals and beta-ketoester-derived tert-butyl (1Z,3E)-1,3-bis(TMS)dienol ethers.

We developed an efficient, practical, robust method for the regio- and stereoselective preparation of (E)-ketene trimethylsilyl acetals (KSAs) derived from tert-butyl esters 1. The reaction was performed under convenient reaction conditions; LDA-TMSCl, 0-5 degrees C, and cyclopentyl methyl ether (CPME) solvent. Two kinds of (Z)- and (E)-KSAs derived from alpha-oxygen and alpha-nitrogen-substituted tert-butyl esters, respectively, were also obtained in good yield. The present protocol was successfully applied to a stereocontrolled preparation of useful, but highly reactive (less accessible) beta-ketoester-derived tert-butyl (1Z,3E)-1,3-bis(TMS)dienol ethers 2.