Rings galore

Yesterday I heard an interesting talk by Professor Rick Danheiser of MIT. Here is a bit of trivia that puts Rick’s contributions to science into perspective: he developed his first named reaction when he was still an undergraduate student. This took place when he was studying chemistry under the direction of Professor Gilbert Stork of Columbia University. The reaction I refer to is now known as the Stork-Danheiser alkylation of the kinetic enolates of beta-alkoxy enones, which should serve as an inspiration to undergraduate students who are interested in organic chemistry: you have a chance to make important contributions at any age.

Over the years, Rick has made many distinguished contributions to the field of organic chemistry. Many of the recent examples were on display in his talk, which I enjoyed a lot. I am just going to mention one case that stems from his 2010 JACS report. The reaction shown below should be a great question on any cumulative examination. You see a fairly rich, “triple bond-endowed” molecule that undergoes cyclization leading to the formation of a tricyclic pyridine-containing system. A curious thing is that one would probably expect some metal to orchestrate ring-forming events of this kind, yet there are no metals in this purely thermal process. As you might suspect, there is an important role attributed to one of the hydrogens in this molecule. Overall, the process amounts to an ene reaction followed by a Diels-Alder process. Or is it the other way around? Take a look as both pathways are conceivable.

klk

http://pubs.acs.org/doi/abs/10.1021/ja106901u

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