Who Art Thou Chemist: Victor Snieckus

This next chemist I would like to introduce is Victor Snieckus of Queen's University in Kingston, ON. http://www.chem.queensu.ca/people/faculty/snieckus/

I have personally benefited from this man's work. Snieckus is most famous for the pioneering work that he and his group have done on directed ortho metalation. 

Aromatic rings are extremely common in a wide variety of important synthetic products. Many natural products that have medicinal properties contain aromatic rings. Acetylsalicylic acid (asprin) has an aromatic ring in it. Important to the research that I am doing: polymers that are used in LEDs also have aromatic rings. This means that it is really important for synthetic chemists (like myself) to be able to rearrange bonds on aromatic rings and attach other things to them. But the problem is that aromatic rings are stupidly stable and don't really like having their bonds broken so you need a really strong base, like butyllithium (BuLi). The next problem is that on an aromatic ring there are six possible sites for making bonds. The trick for synthetic chemists is controlling which site the bonds are made at. This is where directed ortho lithiation comes in. The reaction is directed to the "ortho" position on the aromatic ring.

List of the different positions on an aromatic ring

Example reaction of a directed metallation

 DMG stands for Directing Metallation Group. By having one of these on the aromatic ring, a chemist can be sure that their metallation occurs at the "ortho" position over the meta and para positions. Take a look at the scheme below. Here we see an example of an ortho lithiation. When BuLi is added to the aromatic ring, the DMG directs it to the ortho position and the BuLi removes the hydrogen atom, leaving the carbon atom it was attached to with a negative charge and really reactive, ready to react with the next compound, in this example it reacts with carbon dioxide (CO2). The result is that there is carboxylic acid attached to the aromatic ring. This aromatic ring looks very much like asprin. This reaction is extremely versatile. It is definitely an important tool in the synthetic chemist toolbox. The Snieckus is always coming up with variations and expansions on this interesting and useful reaction. 

I have personally had the opportunity to discuss this reaction with Snieckus and have him give me some advice. He was a visiting speaker at the University of Alberta and I was able to catch him after his lecture to ask him about a directed metallation reaction that I was having problem with. He was able to give me some great suggestions and had a graduate student of his email me a procedure that was part of the students thesis, but hadn't yet been published. He also gave away one of his group t-shirts to a lucky attendant of his lecture and I happened to win since I did lithiation reactions. It was very helpful.

Selected Publications:

Org. Lett., 2010, 12, 2198-2201

Chem. Eur. J. 2010, 16, 8155-8161

 
Org. Lett. 2010, 12, 68-71