Insect pheromones photochemical

Enantiomerically enriched formyl irimclhyleiiemethane -irontricarbonyl complexes add to allylzinc bromides with high stereoselectivity. This was used, after photochemical deprotection, in an enantioselcctive synthesis of the insect pheromone (-)-ipsdienol4s. 

Intermolecular addition of radicals, generated by photo-electrochemical catalysis, to activated alkenes can also be brought about. The reaction of 66 is used as a key step in one synthesis of the insect pheromone, brevicomin [219]. The reaction of a secondary radical from 67 occurs at low cathode potentials and without photochemical assistance [219]. This illustrates the equiibrium between a secondary al-kylcobalt(m) species and the radical - cobalt(ii) pair. The carbon radical is eventually captured by reaction with the alkene. Further steps in the synthesis lead to four isomers of the pheromone, multistriatin, each of which is a pure enantiomer since... 

Photochemical cycloadditions have been among the least widely studied cycloaddition reactions of carbohydrate derivatives, however, some noteworthy examples have been described in the earlier as well as more recent lierature.. Photoannulations of pyranoid enones with both vinyl acetate and ethylene have been described by Fraser-Reid, Hicks, and Primeau 49). Cycloaddition of vinyl acetate to 86 gave the cyclobutano pyranoside 87 as a mixture of diastereomers. This reaction was explored as an approach to the asymmetric synthesis of the insect pheromone grandisol. 

Synthesis of those insect aggregation pheromones having bridged structures may have important economic consequences. Multistriatin (120) is an aggregation pheromone of a European elm bark beetle. A stereoselective synthesis "" has been reported from tartaric acid. A delightfully simple synthesis " of frontalin (121), a pheromone of the pine beetle, is by photolysis of heptane-2,6-dione in methanol-titanium chloride. We also note further photochemical studies... 

One aspect of the current work on chemical control of insects centers on the use of sex pheromones as lures. Recently, chemists at the U.S. Department of Agriculture s Boll Weevil Research Laboratory isolated and synthesized components of the sex attractant of the male boll weevil, a pest responsible for a prodigious loss of cotton crop in the United States. A stereoselective synthesis of the active pheromone was later carried out at the Zoecon Corporation, and is outlined below. A key feature of this synthesis is the photochemical cycloaddition of ethylene to 3-methylcyclohex-2-enone, followed by oxidative disconnection of the resulting c/s-fused bicycio[4.2.0] octane (A) thereby generating the cis disposed side-chains. 

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