Synthesis of the housefly sex attractant.
When we have two carbonyl groups adjacent to a methylene group, the acidity of the -H is greatly increased. Because of the acidity of their methylene (CH2) hydrogens, malonic esters, ethylacetoacetate and -dicarbonyl compounds etc are often called active hydrogen compounds.
Muscalure and related compounds.
The use of such enolate anions from carbonyl compounds is fundamental to organic synthesis and you will already have met them as intermediates in the Aldol reaction and Claisen condensation.
Most important use is for preparation of ketones (from -keto esters RCOCH2CO2Et) and of acids from malonic esters (CH2(CO2R)2).
The Pherobase: Database of Pheromones and Semiochemicals.
Also FGI’s often correspond to some simple types of reaction e.g. reduction (NO2 to NH2), oxidation (CH3 to COOH), diazonium chemistry (NH2 N2+ Ar-X).
El-Sayed. Page created on 5-January-2018
With Aromatic systems the SM’s are usually fairly obvious. Usually benzene or a benzene derivative such as toluene, phenol etc. bond to be disconnected is almost always the bond joining the aromatic ring to the rest of the molecule.
Stereoselective synthesis of some insect sex pheromones.
Reactions are usually straightforward (SEAr) and you will have met most of them before. Synthesis is simplified because the nature of the starting materials is usually clear. Thus, most reactions correspond to the following disconnection:
A student synthesis of the housefly sex attractant.
We have discussed the regioselective reactions of this active methylene carbon (C-2) in ethylacetoacetate. Can regiospecifically trap C-4 via the dianion.
The synthesis of insect sex pheromones.
We will illustrate this approach with examples, starting with synthesis of benzene derivatives. Starting point is usually fairly obvious – simple benzene derivatives or perhaps benzene itself.
A synthesis of muscalure, the housefly sex attractant.
In planning a synthetic strategy, apart from devising a means of constructing the carbon skeleton with the required functionality as above, there are other subtle factors, which we must address.
Convenient method of preparing higher dialkylacetylenes.
– the process of writing one functional group for another to help synthetic planning and to help disconnection. Note, there must be a good reaction in the reverse (forward!) direction.