Practical and Robust Method for Regio- and Stereoselective Preparation of (<i>E</i>)-Ketene <i>tert</i>-Butyl TMS Acetals and β-Ketoester-derived <i>tert</i>-Butyl (1<i>Z</i>,3<i>E</i>)-1,3-Bis(TMS)dienol Ethers

Abstract

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.