REACTION OF KETENE ALKYL TRIMETHYLSILYL ACETALS WITH DIMETHYL ACETYLENEDICARBOXYLATE CATALYZED WITH ZIRCONIUM TETRACHLORIDE

When dimethyl acetylenedicarboxylate is reacted with ketene alkyl trimethylsilyl acetals in the presence of a catalytic amount of zirconium tetrachloride, dimethyl 2-alkoxycarbonyl-3-alkylidenebutanedioates are afforded. Although the silyl enol ether from acetophenone undergoes the same type of reaction, other trisubstituted silyl enol ethers such as those from butyrophenone and 3-pentanone fail to react with dimethyl acetylenedicarboxylate under these conditions.