Prepn. of E,Z-dienes including insect pheromones - starting from alpha-cyclopropyl alpha-alkynyl alcohols

摘要

Stereoselective synthesis of 12-16C E, Z-diene cpds. of formula (I) is described. (where n = 1-10; R is alkyl; R' is H or COR"; R" is lower alkyl). The process comprises first complexing an alpha-cyclopropyl alpha-alkynyl alcohol with Co2(CO)8, treating the complex with a mixt. of a protonic acid and a Zn halide, and decomplexing the resulting halide with Fe(NO3)3 to give a halo-enzyme of formula (IV): (where X is halogen; R' is an H2 atom or CH3 (sic)). Cpd (IV) is then reacted with a Grignard reagent of formula XMg-(CH2)n-O-R'" (where R'" is tetrahydro-2-pyranyl (THP) when n 3 or 1-ethoxyethyl when n = 3) in the presence of Li2CuCl4 in THF. The prod. is hydrolysed with alcoholic p-toluenesulphonic acid and recrystallised to give a stereochemically pure E-enzyme, which is partially hydrogenated to give (I). 1-Acetoxy-7E, 9Z-dodecadiene (Ia) is the female sex attractant of Lobesia botrana.