A Supplement For That Anemic Asymmetric Synthesis

Hi everyone, I hope everyone is doing fine.   How many of you can think of reactions that include iron ?  It is the one of the most abundant elements on earth and yet I scratch my head and can only think of two times when I have used iron in an organic synthesis.  I bet one of the reactions that you have used iron is the reduction of a nitro compound to an amine.  Another reaction that was central to my undergraduate project where I had used iron is a Friedels-Craft reaction with ferrocene to replace the cyclopentadiene with an aromatic ring.  I thought it was a pretty cool reaction back then.  I don’t think I have covered asymmetric reactions in a long time.  What better opportunity to introduce a series of catalysts that no one would have thought could used asymmetrically, right now.  I found it particularly surprising to realize that iron could be used in other ways and I have to say I was a little more than curious when I came across the following article, “Asymmetric catalysis using iron complexes – ‘Ruthenium Lite’?” by Muftah Darwish and Martin Wills, Catal. Sci. Technol., 2012, 2, 243-55.

I am all for optimizing cost and exploiting chemistry using the more common elements.  I could image that by utilizing some of these iron catalysts in place of ruthenium would bring down the cost of any synthesis, provided similiar results were obtained.  I will show some of the best reactions I came across in the paper and perhaps, you might be encouraged to give this paper a look.  You never know, you might be able to use one of these reactions sometime.

 

redox-1

I know, you will tell me that some of these reactions do not produce achiral products.   I just found it neat that you could use the same iron catalyst for a hydrogenation of a ketone as well as an oxidant for an alcohol.

Here are a few more excerpts from the paper.  I had no idea that iron could be used this way and that is why I think this paper is a great find.  The paper covers asymmetric hydrogenations, asymmetric hydrosilylations, transfer hydrogenations, enantioselective epoxidations and oxidations.

 

 

epoxide

 

 

 

 

 

asymmetricred

I have been made a believer that iron has a place in asymmetric syntheses.  Happy Easter, everyone !!

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