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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Richard Jeong on January 04, 2019, 02:52:42 PM

Title: carbonyl coupling reactions
Post by: Richard Jeong on January 04, 2019, 02:52:42 PM
Hello and happy new year!

I am recently interested in Mcmurry coupling, which uses Ti(III) or Ti(IV) with Zn or other metal to couple two carbonyl groups into a double bond. Since I am currently working for transition metal catalysts, especially for reduction, this reaction feels attractive.
My question is, is there any analog of different metals that can couple carbonyl compounds this way?
Thank you for watching this topic, and again, happy new year!

(image from https://en.chem-station.com/reactions-2/2014/08/mcmurry-coupling.html)
Title: Re: carbonyl coupling reactions
Post by: CKabes on January 11, 2019, 02:22:47 AM
Magnesium can do this with aldehydes. This is usually called the Pinacol coupling.
Title: Re: carbonyl coupling reactions
Post by: pgk on January 11, 2019, 08:28:36 AM
TiCl4 is a strong Lewis acid but easily reducible to TiCl3.
Zn powder is an effective reducing agent.
Mg powder or chips can easily form organometallic compounds via an intermediate, free radical step.
Thus:
1). Study carefully the mechanisms of McMurry coupling, Pinacol coupling and Clemmensen reduction and see what is the role of the above metals, therein.
2). Search for alternative metals and/or their salts that have similar properties with Zn and TiCl4 and which could replace them (say Sn and ZrCl4, respectively?).
Hint: Firstly, check their neighbors in the periodic table, before searching for more exotic metals like lanthanides and actinides.
Good Luck!
Title: Re: carbonyl coupling reactions
Post by: Richard Jeong on January 13, 2019, 02:53:53 PM
TiCl4 is a strong Lewis acid but easily reducible to TiCl3.
Zn powder is an effective reducing agent.
Mg powder or chips can easily form organometallic compounds via an intermediate, free radical step.
Thus:
1). Study carefully the mechanisms of McMurry coupling, Pinacol coupling and Clemmensen reduction and see what is the role of the above metals, therein.
2). Search for alternative metals and/or their salts that have similar properties with Zn and TiCl4 and which could replace them (say Sn and ZrCl4, respectively?).
Hint: Firstly, check their neighbors in the periodic table, before searching for more exotic metals like lanthanides and actinides.
Good Luck!

That would help a lot! Thanks!
By the way, my professor and group are currently working with nickel and cobalt. It would take a lot of effort to tell this topic.
Title: Re: carbonyl coupling reactions
Post by: pgk on January 14, 2019, 05:52:36 AM
It doesn’t seem a bad idea because both Ni and Co halides are used as dimerization catalysts.
Besides both Ni and Co belong in the same period of the periodic table as Ti.
Furthermore, Ni-Raney is a dehalogenation catalyst.
It might work.