Clipping nitrogen atoms

I am virtually certain that, as I type this post, there are reactions involving sodium azide being run in my lab. We use this versatile reagent to generate organic azides that are subsequently converted into a gamut of nitrogen-containing building blocks. We are obviously not the only ones who rely on this silver bullet of a nucleophile (to paraphrase my mentor, Barry Sharpless). In fact, the vast majority of synthetic and biological chemists probably use sodium azide in order to make organic azides and later run click reactions with alkynes. While my lab does not run these cycloaddition processes, we like to reduce our azides to amines. In the course of this reaction we lose two nitrogen atoms off an azide and gain two protons. What if we want to “chop off” only one nitrogen atom? I was thinking about a reaction that would correspond to such a transformation earlier today and recalled to mind a really cool process reported by Professor Ron Raines of the University of Wisconsin several years ago. In it, an organic azide interacts with a carefully designed phosphine reagent shown below. The leaving group attached to the carbonyl group enables intramolecular formation of a five-membered intermediate that collapses to release the diazo product. The authors refer to this reaction as “deimidogenation”. Azides are indeed very versatile and multifaceted intermediates. I think we should put this reaction to good use…

Image

http://onlinelibrary.wiley.com/doi/10.1002/anie.200804689/abstract

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