When I met with Professor Greg Dudley’s students two weeks ago at Florida State University, I was pleased to learn about the general utility of their fragmentation method to access medium sized rings. This chemistry employs vinylogous acyl triflates shown below. Upon halogen/lithium exchange and subsequent addition to the ketone, the intermediate lithium alkoxide fragments to generate a 9-membered ring. Looking at the ChemDraw rendering of this molecule does not give it all the credit it deserves. This crystallogaphically characterized ketone features a transannular π to π* interaction between the electron-rich alkyne and electron-poor ketone units. This proximity has consequences and allows various transannular reactions to take place. I am showing just one of them. As you might imagine, the primary application of this strained system is in bioorthogonal chemistry. But I got the biggest kick out of the unusual spatial arrangement between the π systems. Molecules of this kind are rich in chemistry.

http://pubs.acs.org/doi/full/10.1021/jo300188y?src=recsys