[azmanam]

Thanks to tmartin for a stimulating problem in my absence... I'm back this week.

QUESTION: Provide a mechanism, X, and the product.  As a hint, if R1 and R2 are both methyl groups, the 13C NMR of the product shows two peaks, one at 75 ppm and one at 3 ppm.

[Oxy]

I don't sure about the last step. But I think it's the true product.

[stewie griffin]

Oxy, I had your same intermediate as X... but if R1 and R2 are methyls you won't see only 2 signals in the C13 NMR. So I don't think it can be correct can it?

[Oxy]

There are only two types of carbon, only two signals, aren't there ?
Here is 13C-NMR of but-2-yne, predicted by CS ChemDraw .

[stewie griffin]

Ha, this in interesting. I was assuming azmanam meant that the "product shows two peaks.." was referring to the intermediate X. I suppose it makes does more sense if you read it the other (way as in the product is the final product of the sequence.  )

[Dan]

Stewie, I was going to post the same thing earlier, but then realised the 13C data referred to the final product - glad to see I'm not the only one!

[Oxy]

I made some correction of the last step:
This is the first time I meet nitrous oxide as a by-product in an organic reaction...

[azmanam]

Correct, oxy.  that is the both X and the major product.  Good work.  The authors propose a breaking your last step in to two, but the overall transformation is the same.

http://dx.doi.org/10.1039/b203383f