Cycloadditions 4-pyrones

Finally, in a very recent disclosure, Lee et al. (165) approached the total synthesis of arteminolide using a [5 + 2] cycloaddition strategy with an oxidopyrylium ion. Despite its long history of use, Lee was the first to utilize an allene moiety both in an intra- and an intermolecular cycloaddition with oxidopyrylium ions. By utilizing a pyrone cycloaddition precursor (294) similar to those used in the Wender phorbol synthesis, Lee was able to synthesize various ring sizes and... 

We thank the NSF and the NIH for support of our research at Johns Hopkins University on fundamental aspects and synthetic applications of pyrone cycloadditions. 

A strategy for the synthesis of highly substituted anilines and o-phenylenediamine derivatives has been developed based on pyrone cycloaddition with acetylenic dienophiles (Scheme 16.36) [39]. 

SCHEME 16.36 Synthesis of highly substituted anilines from 2-pyrone cycloaddition. 

SCHEME 16.37 2-Pyrone cycloaddition to silicon-bridged cyclophane. 

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