Category Archives: Iron catalysis

Reductive Olefin Coupling

In a new JACS paper J. Lo, Y.  Yabe and P. Baran describe a practical catalytic reductive olefin coupling.

redox

Using a Fe(acac)3/Phenylsilane system at 60°C the reaction above proceeded to produce the shown product exclusively in reasonable to good yields.

The supplementary material is full of pictures of this reaction, including TLC, reagents, work-up and a video on the blog page (for link see this page). The inclusion of such detail in the supplementary material is a new positive change and is to be complemented. Perhaps this is due to the experience they (Baran) had with Blog Syn last year.

Looking at the experimental procedures it seems that this reaction is very dilute, 1 mol starting material in 21 L of solvent (if my conversion is correct) with 30mol% of the Fe catalyst and 2.5 equivalents of phenylsilane! Now if one were to actually do a large scale reaction, say 10Kg (about 50 mol) these figures translate to enormous quantities of material about one cubic meter of solvent. Instead of fiddling about with 10s of mgs of material I would have liked to see the gram unit being used more frequently in the experimental procedures. The video shows a curious experimental technique, where everything is tossed in together, or at least rapidly in an open vessel. Now, I appreciate that they are trying to demonstrate the reaction’s insensitivity towards oxygen but the video shows a rather sloppy way of doing a chemistry experiment. As all the components are mixed together and simply heated there is absolutely no control of any exothermic reactions that may be going on. Now this is ok for 20mg, but what about 20g or 20kg? I would have liked to see something about this in the paper. Now I know it’s not the job of research to do process development but I think that a little closer examination of the reaction parameters would have added to this chemistry.

Still, in spite of these criticisms this methodology is a valuable contribution to the arsenal or reactions available. I hope this gets picked up by industry and it would be nice to see a future OPRD paper discussing this chemistry.

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