Highly selective synthesis of vitamin A and its derivatives. Critical comparison of some known palladium-catalyzed alkenyl-alkenyl coupling reactions

Article abstract of DOI:10.1016/S0040-4039(00)93574-3

Vitamin A has been synthesized cleanly and selectively with essentially complete control of stereo- and regiochemistry in four linear and six overall steps from β-ionone and (E)-3-methyl-2-penten-4-yn-1-ol via Pd-catalyzed cross coupling of an alkenylzinc with an alkenyl iodide; the use of other metals, such as Al, Zr, Mg, B, Cu, and Sn, being inferior to that of Zn.