[zuriel]

Hi guys,

I'm wondering if anyone can give me a hint or a little push with this question. I'm honestly scratching my head trying to figure out the chemistry. I have an extremely vague idea.

From step one I can note the use of triflic anhydride (strong electrophile) and 2,6-di-tert-butylpyridine (a hindered base).
I am guessing there is an

1 - introduction of the triflyl group, followed by
2 - a reduction with diisobutylaluminium hydride
3 - protection with t-BuCOCl
4 - Oxidation using CrO3
5 - I can only pick out the deprotection here with potassium carb. (or is that even correct??) - completely lost here.

Any and all help is appreciated greatly. 

[discodermolide]

I would guess that the first step is formation of the enolate of the ketone where the resultant OH is protected with Tf. Then the ester is reduced.
Perhaps you can follow on from there.

[zuriel]

Hi discodermolide, I have drawn up this scheme here. Can you check to see if it looks OK?
In the first molecule there is a double bonded oxygen there as per the starting material in the question - it's just hard to see with the contrast.

Thank you for pointing me in the right direction!

 

[discodermolide]

Yep, that's what I had worked out.

[zuriel]

Awesome, thanks once again.
I have one other problem that I need some inspiration with. Do you mind if I post that too for some clarification?

 

[Dan]

Awesome, thanks once again.
I have one other problem that I need some inspiration with. Do you mind if I post that too for some clarification?

Please do

[zuriel]

Thanks Dan!

[ashmus]

Just a minor mistake, but there's an oxygen missing after step 3.

[zuriel]

Just a minor mistake, but there's an oxygen missing after step 3.

Where specifically?
After step 3 is step 4 which is an allylic oxidation at the position shown. Are you suggesting that it's possible for the other allylic position to be oxidised too?

[Dan]

The alcohol pivaloylation step, your structure shows RCH₂Piv - should be RCH₂OPiv.

[zuriel]

Ah YES! Sorry guys, late in the evening for this. Thanks for spotting that. 

[ashmus]

Sorry...exactly what Dan said. You also shifted the CH2OPiv group a carbon over (product in step 3) and then moved it back in the next step (product in step 4).