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.

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Ketenes and derivatives P 0230 Practical and Robust Method for Regio-and Stereoselective Preparation of (E)-Ketene tert-Butyl TMS Acetals and β-Ketoester-Derived tert-Butyl (1Z,3E)-1,3-Bis(TMS)dienol Ethers. -(OKABAYASHI, T.; IIDA, A.; TAKAI, K.; NAWATE, Y.; MISAKI, T.; TANABE*, Y.; J. Org. Chem. 72 (2007) 21, 8142-8145; Dep. Chem., Sch. Sci. Technol., Kwansei Gakuin Univ., Sanda, Hyogo 669, Japan; Eng.) -Jannicke

The NaOH-catalyzed first sequential Mukaiyama-Michael reaction/crossed-Claisen condensation is developed using two molar ketene silyl acetals and one molar alpha,beta-unsaturated esters in either a stepwise or one-pot manner.

A sequential Mukaiyama—Michael reaction and regioselective crossed‐Claisen condensation to afford 1,3,7‐tricarbonyl scaffolds is developed using two equivalents of ketene silyl acetals (II)/(IV) and one equivalent α,β‐unsaturated esters (I) in either a stepwise or one‐pot procedure.