[Rutherford]

Tetramethrin is a key substance of many household insecticides. This compound belonging to pyrethroids of the 1st generation can be obtained by esterification of chrysanthemic acid with alcohol X. Synthesis of the latter is given below.

Write down the structural formulae of O-R, and X. Note that the transformation of O into P is an isomerization with retention of the carbocyclic skeleton leading to the most stable isomer.

What is the first reaction about (anhydride+alkene)?

[discodermolide]

It is a Diels-Alder reaction.

[Rutherford]

Read now about it. Found very scary example, but this one seems fairly easy. I think that O is the compound attached. What happens in O P? It is isomerization, but what is the stablest isomer?

[discodermolide]

That's the correct structure. The next step is a series of C=C migrations catalysed by Pd so what is liable to be the most stable isomer?

[Rutherford]

Don't know. This seems like stable to me. The double bond requires an angle of 120°, and in the ring with 6 C atoms, the angle is perfect. What would be more stable?

[discodermolide]

How about the double bond in this structure?


bloddy Smiles won't draw it how I want!

[Rutherford]

I think it's the delocalization, right?
I think that R is the attached compound. If it is, what happens in the last step with formaldehyde?

[discodermolide]

Yes conjugation
That compound is not R

[Rutherford]

What happens then with ammonia? I thought that it is an acid ahydride amonolysis to produce amide and acid.

[discodermolide]

I think it re-cyclises to


You can take


with ammonia to give

[Rutherford]

Wait, I think it gives the compound I wrote, but on heating (t), a water molecule leaves, and the compound you wrote is made. Is this the final product (attached). I thought that the hydrogen attached to nitrogen is acidic because of nitrogen and it leaves the molecule, then N^- is made, and in an nucleophilic addition the compound I attached is made. True?

*Forgot the double bond  .

[discodermolide]

That will do.
That is the final compound.

[Rutherford]

Okay, thanks.

[Rutherford]

Which of the following acid derivatives could easily form esters in reaction with alcohols?
a) anhydride; b) methyl ester; c) amide; d) hydrazide

I would say a). Not sure for c) and d). How to determine this? What property to aim for?

[discodermolide]

You need to look for good leaving groups and the reaction conditions.
certainly a), other esters can be formed form methyl esters by transesterification, you can't usually form esters from amides, nor hydrazides