[phth]

Sorry for the wait.

[Altered State]

Here is my attempt.
I wasn't sure about starting materials, so I started from the simpler stuff I could, I'm pretty sure that some intermediate is accessible in an easier way. Besides I guess there are several ways to get to the cyclation triene, but this is the first I thought of...

Problem is last step, I would be surprised if it yielded the correct TM. Anyway, here it goes:




I'll try to come up with something better during the week

[Altered State]

It seems like I cannot edit my post.

Here is a better way to get to the triene:


This makes 6 steps overall.
The starting aldehyde is commercially available as its acetal form.

I've been thinking about the conformation of the TM, and maybe it's not that unlikely that the product forms after all, in case the double mCPBA epoxidation proceeds correctly.

[AlphaScent]

Altered State:

Can you by chance post some detail to your last two steps? 

How to get to the bromohydrin via bromine?  Ive done NBS and water.  I do not see how that works.

I am also not that enlightened with the mechanics of metathesis chemistry.  Do two molecules come together to form the triene? 

[Altered State]

Altered State:

Can you by chance post some detail to your last two steps? 

How to get to the bromohydrin via bromine?  Ive done NBS and water.  I do not see how that works.

I am also not that enlightened with the mechanics of metathesis chemistry.  Do two molecules come together to form the triene?

Its not a bromohydrin formation, its just a alpha to carbonyl halogenation. Then, (yes, I forgot to put H3O+ to hydroxide the imine, wops) the imine hydrolysis gives the aldehyde again, which can tautomerize in the resulting enol (similarly to the first equilibrium on the top of that picture).
Really it doesn't matter how shifted are the ketoenol equilibria, since the other alkenes are the ones which participate on the next reaction.

Olefin methatesis it's a beautiful and great reaction in which to alkenes react to give two new alkenes on the following way:

http://en.m.wikipedia.org/wiki/Olefin_metathesis#/image/File:Metathesis.png

So the reaction would give the triene and also ethylene.

http://en.m.wikipedia.org/wiki/Olefin_metathesis
They gave Grubbs and Schrock the Nobel Price in 2005 for this.

[kriggy]

It could be also bit wild if you are not doing ring closing or connecting two same alkenes.

Im also not realy sure about the bromination. I would expect addition on the double bonds rather than amine substitution. Do youhave any literature to support it? (Not saying it wont work)

[phth]

@Altered state, I think the MCPBA step is like 90% de if the up facing acetate is a hydroxyl (stabilizes the transition state by h-bonding), but I think there still should be a better preference for the up face.  Ill submit a try later.

[Altered State]

It could be also bit wild if you are not doing ring closing or connecting two same alkenes.

Im also not realy sure about the bromination. I would expect addition on the double bonds rather than amine substitution. Do youhave any literature to support it? (Not saying it wont work)

About the methatesis, I'm not sure, I'm just guessing, but I think that the fact that the aldehyde-enol alkenes will be probably shifted towards the aldehydes, will be easier for the only other two olefins to react.
Then, when the molecule joins, the extra stability of triene will make easily possible the electrocyclation. I respect that it's just guessing.

About the bromination, I guess you're right, addition to alkene might be a problem.

I've found these alternative methods here, that probably would fit for the purpose:



http://pubs.rsc.org/en/content/articlelanding/2005/cc/b509366j/unauth#!divAbstract

Edit, and if not possible, I guess you could always start from another thing and make the double bond after bromination

[phth]

I got this problem from 'The Logic of Chemical Synthesis'.  I haven't looked at the answers yet, but there are 4 ways reported which I can post at the end if anyone is interested.  I think the biggest flaw with my synth is 2 steps are not that stereoselective:

[kriggy]

Could you post some info about the reactions with MeI (-NMe₂+MeI  iodocompond and the cyclization ?
Thanks

[phth]

For the NMe₂, I guess an eq of I₂ would be needed, but I was just trying to make a leaving group there.  The cyclization creates S⁺Me₂ which can form a ylide.  Then addition followed by elimination.  The same reaction works for michael acceptors forming cyclopropane rings.

[Altered State]

Well, I took your feedback into consideration and came up with this last attempt in 9 steps. This would be a bit more stereoselective.

I'm done for this week

[sjb]

All those stereocentres are crying out to me for use of some sugar chemistry. Any thoughts along that line?

[kriggy]

Ok my try. There are some issues with it but Im tired so maybe tommorow I´ll try to fix it.

[Altered State]

Would that epoxydation step work, even in poor yields?