On acyl radicals

On this gloomy Friday evening in Toronto (accentuated by the fact that we were supposed to go to the movies with my wife, but I purchased the tickets online to the wrong theater…), I am going to talk about some thought-provoking radical chemistry. Earlier today, I was talking with my PhD student Jeff about some radical-related matters relevant to our own research. This discussion brought to light a paper that I have always found fascinating. The work deals with facile generation of acyl radicals. Acyl radicals are not that uncommon, especially when generated from seleno- and thioesters. However, radical cleavage of an aldehyde’s C(sp2)-H bond is a less precedented reaction that raises a few eyebrows. Back in 2005, Tomioka and colleagues reported a marvelous example of this process. In their efforts to add nucleophilic thiol-derived radicals to double bonds (with the ultimate hope of making 6-membered rings), the authors serendipitously discovered that thiol radicals prefer to abstract the aldehyde’s hydrogen, leading to facile generation of acyl radicals directly from aldehydes. The resulting intermediate went on to form the cyclopentanone shown below. Several years ago, Stoltz and co-workers put this chemistry to good use in their synthesis of cyanthiwigin F (http://www.nature.com/nature/journal/v453/n7199/full/nature07046.html).



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