[Heory]

the diene nucleophile is just like that in Prinse reaction, but here it may be a side reaction. if the answer was as simple as the acetal, i would be crazy

[azmanam]

couldn't sleep?

haha.  all that functionality just for an acetal formation?  that would be an awesome trick question.  The acetal is the initial product of the diol/aldehyde/L.A.  Once formed, the diol will continue to react.  We're on the right track now.

[nj_bartel]

The acetal formation in this case is allowed to proceed to an appreciable extent due to the carbonyl oxygen coordination to the boron complex, yes?

[azmanam]

yup, lewis acid activation lowers the activation energy for addition to oxonium ions.  loss of water gets us to the acetal

[Heory]

another guess:

[nj_bartel]

What's the leaving group in that last step?

O⁺-B^--F₃?

[Heory]

something was wrong and i'll think of it for some time

[Heory]

q

[azmanam]

nope . my hint for the second step of the mechanism: remember that acetals are in equilibrium

[Heory]

It's quite a difficult work to predict the product, because many paths exist for the reaction. If this is still not right, I'd like you to tell me more information about it.

[azmanam]

you've got the right transformation (which named reaction is this?), but the wrong regiochemistry.  why did you choose that c-c bond to make?

[Dan]

Hmmm. Good work on the acetal Heory!

Something like this?

This terpene stuff is making me itch for a hydride shift... but I can't see a good oppertunity.

[azmanam]

that's the right C-C bond formation.  The orientation of the alkene-containing side chain will be dictated by steric clash with the isopropyl group... but the diene-containing 6-membered ring will not adopt a chair conformation, so we'll need to rethink the origin of selectivity in the c-c bond forming step (still need a name for this reaction).

The chemistry after the c-c bond forming step is not correct yet.  different things happening here.  getting closer

[Heory]

 

[azmanam]

you're correct up to your last step.  Still looking for a name for the c-c bond forming step (and there will be a name for the final step).  you've got the right idea, but hydride doesn't transfer.  I think as a result of geometry, but I might have to look at a model.  anyway, we're quite close now.