Regio- and Stereoselective <i>Anti</i>-Carbozincation of Alkynyl Ethers Using ZnBr₂ toward (<i>Z</i>)-β-Zincated Enol Ether Synthesis

(<i>Z</i>)-β-Aryloxyalkenylzincs are synthesized stereoselectively via <i>anti</i>-carbozincation among alkynyl ethers, silyl ketene acetals, and ZnBr₂. X-ray analysis revealed the structure of the zinc species is a mononuclear two-coordinate dialkenylzinc that is transformed into functionalized enol ethers as a single isomer in the reaction of various electrophiles