"Everyone loves neat tricks in synthesis that are not as easy to spot in retrosynthesis as oxidations or reductions; one of these I came across recently is the conversion of furans to tetrahydropyrans, the Achmatowicz reaction, the seminal publication of which was in 1971 in Tetrahedron: This reaction was used in a few total syntheses; besides those mentioned in the Wikipedia article, I particularly like O'Doherty's synthesis of the indolizidine (-)-D-Swainsonine published in Org. Lett. The four carbons that will form the five-membered ring of the bicyclic system was formed using the Achmatowicz reaction. 2-Lithiofuran opened the gamma-butyrolactone to install the alpha-oxygen; a TBS protection allowed for asymmetric Noyori reduction of the ketone, installing the necessary stereocenter for the substituent on the tetrahydropuran for the subsequent steps. The Achmatowicz was achieved using NBS."
- Khalid Mirza
from Bookmarklet
This reaction is an oxidation while ours occurs under strongly acidic conditions.
- Jean-Claude Bradley
Right. What I meant was a TFA catalyzed / initiated oxidation process involving molecular oxygen activated by the acid..something of a sort claimed here.."The catalytic oxidation of organic compounds in superacids"; http://www.springerlink.com/content... Abstract Transformations of aromatic and aliphatic organic substances in anhydrous trifluoroacetic acid (TFA) at room...
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- Khalid Mirza
That is certainly something to keep in mind but I don't think you would have enough O2 in the system for quantitative conversion of the furans. From what I recall furans do react with strong acids and you would have to compare what would happen from the info in those papers.
- Jean-Claude Bradley
Structural and Functional Characterization of Falcipain-2, a Hemoglobinase from the Malarial Parasite Plasmodium falciparum - dx.doi.org/10.1074/jbc.M603776200 http://www.jbc.org/content...