AlCl3-Promoted Facile E-to-Z Isomerization Route to (Z)-2-Methyl-1-buten-1,4-ylidene Synthons for Highly Efficient and Selective (Z)-Isoprenoid Synthesis

Zr-catalyzed methylalumination of 3-butyn-1-ols followed by AlCl3-promoted stereoisomerization at 50 degrees C for 6 h provides 4-iodo-3-methyl-3-buten-1-ols 2b and 6 (>= 98% Z configuration) in 87 and 67% yields, respectively. (Z)-1,4-Diiodo-2-methyl-1-butene (1b) obtainable by iodination of 2b is a valuable synthon for efficient and selective syntheses of (Z)-alkene-containing isoprenoids. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)