Stereospecific syntheses of sex pheromones of the californian red scale and white peach scale (Homoptera:Diaspididae) based on 1,4-cis-hydrogenation of dienes

Chemistry of the pheromones of mealybug and scale insects

“…Vasil'ev et al addressed the alkene stereochemistry problem with a (Z)-selective, 1,4-dihydrogenation of a conjugated diene precursor (Scheme 34). 78 Thus, aldehyde 229, generated in $34% yield in 4 steps from ethyl acetoacetate, subjected to Wadsworth-Horner-Emmons olenation gave triene 230 in $79% yield, as a 65 : 35 mixture of (2E,4E)-and (2Z,4E) isomers. 1,4-Dihydrogenation of this mixture with a methyl benzoatechromium tricarbonyl catalyst gave the desired (3Z)-alkene 231 as the sole product, which was carried through to the pheromone 83 in several straightforward steps.…”

“…84 The synthesis of Vasil'ev et al was identical to their synthesis of the red scale pheromone (See Scheme 34) with the exception that 1-bromo-3-methyl-3-butene was used to make the protected ketoaldehyde starting material in place of 1-bromo-3-butene. 78 Pheromone of the scale Aulacapis murrayae. Ho and coworkers very recently identied the pheromone of A. murrayae as the (R)enantiomer of the degraded irregular terpenoid solanone.…”

Synthesis of insect pheromones belonging to the group of (Z)-trisubstituted alkenes

“…Thus alkylation of the anion 117 generated from isobutenyl phenyl sulfide under the action of Bu s Li with but-3-enyl bromide occurred exclusively at the a position to form sulfide 118. Reductive lithiation of the latter with lithium 4,4 H -di(tert-butyl)- In 1995, Serebryakov and coworkers 58 synthesised the acetate (AE)-72 using the highly selective 1,4-cis-hydrogenation of conjugated dienes in the presence of carbonyl chromium complexes 59 for the construction of the (Z)-trisubstituted C=C bond. This method had been employed previously 60,61 in the synthesis of natural compounds.…”