[AlphaScent]

so in another post I talked about a reaction of 1-bromo-3-pentyne and a grignard of 11-undecyn-1-OTHP with copper iodide mediating the coupling. In theory it was a 6 step synthesis to my product, (10E,14E)-hexadecadienal.  My synthesis was a failure.  I have another idea but it will most likely be theory and is 12 steps. It starts from 1,10-decanediol. I will post it tomorrow morning when im at my computer, im on my phone now.

so, to all of you, how would you synthesize (10E,14E)-hexadecadienal?

[mst]

1) ozonolysis of cyclodecene
2) prepare wittig reagent from 6bromo 2hexene
3) wittig schlosser with excess dialdehyde to avoid double reaction as much as possible

Edit: I think swern/dess Martin of decanediol should be way cheaper for step 1

[AlphaScent]

mst,

I think that is a very smart and efficient way of making this compound.  My only problem is the cost of cyclodecene.  It is from aldrich something like $250 USD for 1 mL.  Again, great way to make it.  Also the alcohol precursor, (4E)-hexen-1-ol is also expensive. 

Below is a tedious, 12 step synthesis that relies on cheap material.  What do you think?  Chemistry is sound.

[AlphaScent]

Followed by reduction of mesylate with LAH giving the 16 C skeleton.  Lastly, remove THP and oxidize with Swern or PCC to final (10E,14E)-hexadecadienal

[mst]

Sorry, didn't know if reactant cost are a big deal to you.

In that cast, like I mentioned in my edit, double swern of 1,10-decanediole is a cheaper way to produce it.

Furthermore I didn't check the price on the bromo-derivate, just saw it's commercially available in scifinder. But (4E)-hexen-1-ol is around 150$ for 25g at sigma aldrich, which isn't really expensive in my opinion. Should still come out cheaper and more convenient than a 12 step synthesis.

[Benzene]

how is this going? what step are you on?

what went wrong in the original grignard coupling?

[AlphaScent]

mst,

You think I should:

1) Diol to Dialdehyde
2)(4E)-Hexen-1-ol to the corresponding bromide (TPP,Br2) or Finkelstein
3) Produce Wittig reagent from Bromide
4) Schlosser modification with excess aldehyde to produce diene system and final product

I am quite taken back at the simplicity and elegance of this if this is viable.  Do you have experience or literature you could have me read to talk about that particular Schlosser modification??  I am intrigued.

I will indeed get back to you on this and if I go ahead with this you will receive the due credit.

Benzene,

I do not know exactly what was happening.  But a majority of my bromide was being consumed.  I believe since the bromide was homo-propargylic that elimination was predominating even though I was lowering the temperature and not using HMPA as a cosolvent.

I had tried to use HMPA along with THF and I was not getting much alkylation. 

What was even more frustrating is that the GC of the reaction was showing 40-50 % conversion but then after workup the peak areas would change to only showing 10% conversion.  That is really what was grinding my gears through the whole synthesis.