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

Who Art Thou Chemist?

This particular post, or rather, series of posts has been inspired by an article in the New York Times http://www.nytimes.com/2011/08/09/science/09emily.html 
It seems that people do not know who leading scientists are. This is a shame since there are great scientist out there, doing work that can have huge implications on daily life. The further implications is the fear that the public has of science. See The Ethical Chemist for further information. I plan to introduce a few interesting chemists so that maybe my loyal readers learn a little about some cool science.


The first scientist I would like to introduce is Marc Hillmyer of the University of Minnesota. http://www.chem.umn.edu/groups/hillmyer/ I was first introduced some of the work by the Hillmyer group at a conference in Australia. I chose to present his work as part of a seminar that was required for my Ph.D. The work that I was most interested in was his work on miktoarm star terpolymers for multicompartment micelles. So what does this mean? The Hillmyer group makes polymers that have three "arms". One arm of the polymer is a water soluble (the term used is "hydrophillic") polymer, like polyethylene glycol. The two remaining arms are both not water soluble (the term used is "hydrophobic"). But what is really interesting is that the two hydrophobic arms also don't mix: one is a hydrocarbon polymer; the other one is a fluorinated hydrocarbon. Think of this like a teflon frying pan and bacon grease. Neither will mix well with water, but the bacon grease (the hydrocarbon polymer) also won't stick to the teflon (the fluorinated polymer). Now these polymers, when added into water will assemble so that the hydrophillic polymers are on the outside, while the hydrophobic polymers are on the inside. Because the two hydrophobic polymers don't mix, they form two different compartments inside. The result are multicompartment micelles. A neat application of multicompartment micelles would be in drug delivery. Two incompatible drugs could be packaged in each of the different compartments and then delivered to the same target. This is just one particular example of a possible application. But my favourite part of this work is the synthesis. I love how this group was able to join all three of these polymers at a single carbon junction.  This is not trivial. I found the synthesis very elegant. 


Selected Publications by Hillmyer:

Liu, C.; Hillmyer, M. A.; Lodge, T. P. – Evolution of Multicompartment Micelles to Mixed Corona Micelles Using Solvent Mixtures – Langmuir 2008, 24, 12001–12009.

Liu, C.; Hillmyer, M. A.; Lodge, T. P. – Multicompartment Micelles from pH Responsive Miktoarm Star Block Terpolymers – Langmuir 2009, 25, 13718–13725. 

 

Li, Z.; Hillmyer, M. A.; Lodge, T. P. – Morphologies of Multicompartment Micelles Formed by ABC Miktoarm Star Terpolymers – Langmuir 2006, 22, 9409–9417.

Lodge, T. P.; Rasdal, A.; Li, Z.; Hillmyer, M. A. – Simultaneous, Segregated Storage of Two Agents in a Multicompartment Micelle – J. Am. Chem. Soc. 2005, 127, 17608–17609.

 I hope that my readers found this interesting. There is lots of interesting science being done out there. This particular post doesn't even cover all the interesting work that is being done in the Hillmyer group.