Near-simultaneous reports of an interesting new pyrrole (and dihydropyrrole) synthesis have appeared recently from the labs of Frank Glorius (Westfälische Wilhelms-Universität Münster) and Naohiko Yoshikai (Nanyang Technologial University, Singapore). Optimization of the additives, solvent, and temperature led to essentially the same conditions from each laboratory. A balloon of oxygen is preferred: yields are much lower when air is used. A Heck-type mechanism is shown, but a Wacker-type mechanism involving nucleophilic attack of an enamine onto a Pd-complexed alkene could not be ruled out.
The scope of the reaction is decent, as indicated below. Failures include R3 = CF3 or cyclopropyl and R2 = Ph. N-Homoallylic and N-cinnamyl imines were also unsuccessful.
Specific examples are shown below:
Interested in having a short course on Heterocyclic Chemistry at your company?
In late 2011, I put together a new two-day short course entitled “Heterocyclic Chemistry – A Drug-Oriented Approach” to present at companies. In a nutshell, it’s an intensive, preparatively-oriented course on the synthesis of the types of molecules encountered in the pharma and agricultural endeavors. There is a heavy focus on practical, proven methodology that people actually use. I keep it updated with lots of current chemistry.
Beyond the two days of instruction at your company, participants are left with a great resource: A book of over 500 slides of information, nicely organized, well-referenced, and containing many specifics on the best ways to make heterocycles.
I’m booking courses for 2013 and early 2014. Learn more by checking out the course web site, where you’ll find more on what the course covers. You can also download a two-page summary of the course to pass around to your colleagues. If you know of other chemists who might be interested in the course, I’d appreciate passing this along. You can reach me at will at pearsonchemsolutions dot com.
Sometimes you just have to step back and marvel at the structures that are found in nature. Check out zamamiphidin A, a new manzamine alkaloid isolated from an Okinawan sponge by J. Kobayashi and co-workers (Organic Letters). Heptacyclic. Quaternary ammonium. Massively bridged. Well done, sponges!