ChemSemBlog

This installment of ChemSem had the honor of hearing Dr. Hisashi Yamamoto of the University of Chicago present on some of the studies he has undertaken in the past. Yamamoto is a world renown organic synthetic chemist with many years of experience. He’s spent many years focusing on developing the science and art of organic reaction syntheses of natural substances.

It is well known that there is much waste involved in standard synthetic organic chemistry. Solvents, catalysts, and other reagents must often be discarded after use. Futhermore, a standard synthesis of a compound generally requires a few to several reaction steps multiplying the volumes of wasted materials. Yamamoto has been focusing on reducing that waste by developing methods of single step syntheses. Though some of the reagents that he uses in his single step processes are more expensive than general reagents, and must also be discarded, the overall cost-benefit analysis shows that the economy of time and material for one step far outweighs the costs of more expensive reagents.

Much of the seminar involved the syntheses of polyketides which are valuable due to the fact that they generally are five times more biologically active than commonly occurring organic substances. Thus, a method for easily synthesizing them, could have significant ramifications on the pharmaceutical industry. Secondly, I thought it was interesting when Dr. Yamamoto pointed out as an example of waste that even the synthesis of Vitamin E which is produced in vast quantities, commonly uses large amounts of dichloromethane for production. Finally, Dr. Yamamoto used super Bronsted acids for portions of his synthesis. When asked about these, he noted that they were very useful, but had not been invented by organic chemists seeking better acids. Instead, it turns out that they were developed by the inventors of Lithium Ion batteries to increase speed of reaction.

Overall, Dr. Yamamoto did an excellent job of presenting the value of single step cascade reactions for synthesis of organic materials. If possible, this could be a very useful tool and could greatly increase the rate of discovery in chemical studies. Much of the intricate chemistry involved was difficult to grasp, but overall the presentation was well received.

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This week’s lecture was done by the famous organic chemist Hisashi Yamamoto from the University of Chicago, known for such things as the Yamamoto reagents and reactions. His presentation was fairly interesting, but it was sometimes hard to understand what he was saying. The reason I found this presentation to be interesting was the topic of the catalysts. I have always found catalysts to be an intriguing subject, and it would be nice to have more lectures on the subject.

One thing that I learned from this lecture was that it only takes a very small amount of base in a reaction or solution to kill the acid catalyst. Something that I would like to find out about is what makes cascade reactions have a one hundred percent economy. This is not typical for many things, but it is interesting that it is almost always the case with cascade reactions.

Another thing that I learned from this lecture was that for cascade reactions there are a lot of solvents and big and “bulky” reactants that are used during the processes. To me this seems like it would be very expensive, but I guess that since the reactions usually produce one hundred percent product, this may not be much of a problem.

If I were explaining the content of this lecture to one of my non-science friends I would probably describe it as a lecture about how chemists can use cascade reactions to produce different chemicals using different catalysts. As for the speaker, it was very enjoyable to have a well-known chemist lecture us, and it would be nice to have a chance to hear Dr. Yamamoto speak again, whether it be here at Andrews or somewhere else.

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Our high profile, award winning guest Hisashi Yamamoto, professor of organic chemistry at the University of Chicago, thinks of new strategies and ways to shorten the number of reactions needed to obtain a product, especially using cascade reactions (the whole reaction takes place in one pot or tube reactor) hoping for 100% atom economy, eliminating side products. His research also includes asymmetric synthesis using acid catalysts (Brønsted and Lewis acids) and the development of efficient syntheses of polyketides for production.

Biologically active polyketides compose 2% of all polyketides and naturally-derived products proved very effective as a therapeutic medicine in certain areas. Due to its highly stereoselective nature, polyketide synthesis normally consists of 50-100 steps and yield only a little amount. Yamamoto’s work researched methods of using their homemade Super Brønsted Acids and Super Silyl to improve the Mukaiyama aldol reaction. Many of the acid catalysts shown were quite bulky and very steric—the steric hindrance acts as a sort of “umbrella”, preventing other reactions from occurring. These acid catalysts proved to be more selective and powerful in reactions as well as being very efficient, needing only a small amount of the very reactive catalyst. Also, Super Brønsted acids can be almost completely recovered, making it a recyclable resource. During the Q-and-A, someone asked about super acids availability (this was the first I had heard of them as well). Apparently, they are not expensive, commercially available, and also easy to make. When Yamamoto told us that it was not organic chemists who had discovered them but the battery companies everyone had a good laugh.

Andrews University includes a number of students whose first language is not English and many of them feel quite uncomfortable speaking in front of an audience because of this. I think that Professor Yamamoto, who came to the United States after receiving his Bachelor degree in Japan, demonstrated good seminar techniques for those students. Taking his time to speak calmly and unrushed, few were the times Yamamoto stumbled over his words. Of course, perhaps it was due to his great familiarity with organic chemistry, having started teaching himself in middle school.

Laymen’s Summary of Chemistry Seminar: Professor Hisashi Yamamoto is an organic chemist who thinks that ridiculously lengthy syntheses that have low percent yields need to change. So he’s looking into super acid catalysts to improve results and massively cut down the number of steps needed to produce polyketides (which can take 50-100 steps ). He believes that the new frontier involves cascade reactions, where all the ingredients for a synthesis go in one pot or reactor tube, taking the shortcutting to a maximum.

I especially liked this interview from the ROYAL Society of Chemistry that Dr. Murray linked to us:

http://www.rsc.org/Publishing/ChemScience/Volume/2009/07/Hisashi_Yamamoto_interview.asp

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Today’s guest speaker for the chemistry seminar was Hisashi Yamamoto. He is an Arthur Holly Compton Distinguished Service Professor at the University of Chicago. He has received various awards in chemistry and published hundreds of articles, reviews, books, and journals.

The title of the presentation was “Designing Asymmetric Catalysis – Cascade Reaction for Polyketide synthesis.” Mainly, Hisashi Yamamoto explained about synthesizing catalysts, which have more power than other catalysts that have existed before. Generally, a catalyst is a chemical substance which is not consumed in the chemical reaction. However, it participates by speeding up or speeding down the reaction through reducing or increasing the activation energy of the reaction. He said that by using strong catalysts, he can reduce the amount of steps needed to make products, which also saves time, money, and materials. Also, I learned that it is important for cascade reactions to have no side products and load very low catalyst.

From his presentation, I found that most of the reactions he did occurred at very low temperature; from -78°C to 0°C. I was wondering if there were any special reasons that the temperature was very low. Does the temperature affect the behavior of the catalyst?

It was interesting that I had a chance to meet a world famous chemist and learn about his passion for his job. He said that he had never thought about having any other career except as a chemist. I want to be as passionate about my work as he is.

I would tell my friends that he is using more effective chemical substances which help speed up reactions.

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This week’s presentation speaker was Hisashi Yamamoto, a professor of chemistry at the University of Chicago. He has made an extremely noticeable achievement in acid catalysis in organic synthesis. Because it was a great opportunity to meet a world-famous organic chemist, I was very excited about his seminar.

First of all, I learned the importance of a cascade approach for organic synthesis. One of the significant topics he spoke about during the presentation was the cascade reaction of an organic compound that needs a lot of steps to be synthesized. If chemists reduce many reaction steps and synthesize the molecule in very few steps, their findings can lead to a great change. To save steps means that they can make the compound efficiently by saving materials and times. In addition, I learned about the “super Brønsted acid.” He mentioned the Mukaiyama aldol reaction, and in order to improve this reaction, he made super acid catalysts. In spite of a small amount of Brønsted acid, the super acid catalyst functions very well  in the synthesis of complex organic molecules.

Another thing I found out was that he successfully made “super silyl” group. Super silyl is so reactive and selective that it provides sufficient reactivity of silyl enol ether and is used as a protecting group in several organic reactions.

One of the questions I had during the seminar was about “chiral” Lewis acid, what chiral Lewis acid catalyst is, and how it works differently when compared to achiral acid catalyst.

I think the seminar was very interesting for me because I could learn a lot from him in terms of acid catalyzed synthetic reactions including Lewis acids and Brønsted acids. Also I would say to my ‘non-science’ friend or family that Professor Yamamoto has developed acid catalysts to improve ease and economy during organic synthesis.

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We were privileged and delighted this week to receive words from the renowned organic chemist Dr. Hisashi Yamamoto. From the start, it was evident that this was to be a stirring lecture and very engaging. Dr. Yamamoto’s love for organic chemistry came at an early age, even in high school. His journey led him to the University of Chicago where he continues his research today.

Dr. Yamamoto spoke to us on the topic of Cascade reactions and specifically in the realm of the biologically-significant polyketides. Employing the use of strong, bulky, homemade acids, Yamamoto’s team has been able to clump what used to be a 3 to 5 part series of reactions into one reaction which retains complete “atom economy,” meaning that there are no byproducts of the reaction apart from the desired product. Not only has this method been successful in yields and general economy, it has also proven to show stereospecificity in the upper 90%’s. Attributing to the economy of this process is the fact that several of the acid species were able to be recycled and reused.

Dr. Yamamoto is clearly passionate about his material, and became increasingly excited about the material as the talk progressed. All those present were engaged and enjoyed his very easy-going upfront persona. Dr. Yamamoto proved very proficient during the Q & A time, showing that he was very aware of most of the ins and outs of his research. Dr. Yamamoto achieves perfect tens in all my areas of “judgment,” which include professionalism, chemistry content and student engagement.

To the layperson, this seminar discussed how to economically make important “life” molecules in the areas of saving time and money.

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The seminar that was held on October 29, 2009 was  called “Designing Asymmetric Catalysis.” The speaker was Hisashi Yamamoto, from the University of Chicago. He is known as a world famous organic chemist. I was impressed that he always wanted to be a chemist; he started to read some university chemistry books when he was a high school student. Later, he graduated and received a bachelor degree at Kyoto University in Japan, and received a Ph.D. at Harvard University. Not only that, but also he has over five hundred original publications and many journal and review articles that have been published.

As mentioned before, his presentation was on designing Asymmetric Catalysis for polyketide synthesis.  In this synthesis, cascade reaction, the “one-pot” reactions is used. Due to cascade reactions, the number of steps in the reaction decreases which also lead to save time and materials for the experiment. Additionally, it does not give side products and it would cause interference in reaction.

I learned new things in this seminar. First, only 1% of polyketides have biological activity and require more than fifty steps to synthesize. Second, different amount of substrate can produce different products. Third, cascade reaction is no side product reaction, giving 100% atom economy.

I also had two questions, first, how long he has been working on this research?  Secondly, what other things would be on 99% of polyketides? However, for the second question, his answer was that 99% of polyketides are selective.

Overall, the topic of this seminar was interesting and it was pleasure to meet a world famous chemist. He was really nice and kind when answering questions. If I can sum up this presentation in one sentence, it would be that cascade reactions can decrease steps in synthesis, which is really beneficial in saving time and materials.

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This week’s seminar was Designing Asymmetric Catalysis: Cascade Reaction for Polyketide Synthesis.  The speaker was Hisashi Yamamoto, an organic chemist, who received his BSc from Kyoto University and PhD from Harvard.  He has held many teaching positions over the years, such as Assistant Professor and lecturer at Kyoto University, Associate Professor of Chemistry at the University of Hawaii, Professor at Nagoya University, and an Arthur Holly Compton Distinguished Service Professor at the University of Chicago.  He has also received many awards over the years.  The presentation was interesting and easy to follow.

One of the new things I learned in this seminar was that when looking at a catalyst it is important not to have any side product and it needs to be highly reactive.  The speaker liked super bronsted acid.  And a small amount of base can kill an acid catalyst reaction.

The other students seemed to be pretty attentive during the seminar and the question and answer period went very well, the presenter was very knowledgeable about his topic.

The presentation definitely encouraged me to learn more about the subject.  However I do not think I would be interested in doing research on it.

I think the reason that this seminar was interesting was because it seemed to have a lot of practical applications. If I had do describe this seminar in one sentence it would be, “world famous organic chemist, Professor Yamamoto presents ways to speed up organic reactions.”

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This presentation was done by a world famous organic chemist, Hiashi Yamamoto. Yamamoto had a mild Japanese accent and soft spoken, but his presentation was very understandable, in which he explained a lot. His current interests are cascade reactions for polyketide synthesis. I found this topic to be interesting and it was amazing that Yamamoto made up some of his own catalysts as well as reactions, such as the super bronsted acid, and the Sakuri reaction. Yamamoto started his presentation by giving a background of acid catalyst and telling of what he wanted to improve. His goal was to modify the acid making it more powerful, selective, and useful.

With the cascade reaction, they used a 1-pot reaction, in which a reactant is subjected to successive chemical reactions in just one reactor. The importance of polyketides are that 1% of them are biologically active, which is five times the average for natural products. Another interesting point was the Mukaiyama Aldol reaction, which can be key for the synthesis of Nyastatin A., Leucascandrolide A, and Tetrafibricin. These methods are three to four steps and were improved by changing the acid catalyst to a super bronsted acid or silyl acid, which are very strong. Yamamoto and his group also performed an excess aldol reaction to see if they can form molecules with large molecular weights. They found that they could make a trialdol, using an iodine benzene complex. This molecule has three chiral centers, making it possible to generate eight stereoisomers of one product. They also performed a sequential reaction from acid to basic in a one pot reaction which I thought was very interesting.

At the end of this presentation many questions were asked, and Yamamoto answered them well. Some students seemed to enjoy the presentation, while others looked as if it was tedious towards the end. I felt that the overall presentation was appealing and I learned a lot about cascade reactions.

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Dr. Hisashi Yamamoto was able to give a rather fascinating presentation this past Thursday in his work with acid catalysts for cascade reactions. I found myself a little bit more hyped up than usual for the seminar this past Thursday particularly from reading his flyer which highlighted his many awards, publications, and patents. Coming into the seminar with pretty high expectations, I was not disappointed at all as he was able to give a captivating presentation that was both easily comprehensible and full of interesting chemistry.

I was able to learn several things during this lecture which were new to me. This idea of using Super Bronsted Acids and the benefits of them seemed really innovative, and it made me understand why Dr. Yamamoto was such a great chemist. No side products and very low catalyst load brought considerable benefits to the synthesis of complex molecules like polyketides. He was able to use one pot, while drastically cutting down the synthesis time. Other interesting things that I was able to get from this presentations were that since only a very small amount of catalyst was used, sequential basic reactions are able to be done in one pot. For example, a Grignard reaction was able to be done in the same pot.

Despite a softer speaking voice than past lecturers, Yamamoto was still able to take command of the audience’s attention. This was probably accomplished from the understandable and exciting research that he presented. He was able to answer the questions we had for him, and I was able to get more information from the questions asked as well. For example ,I found that their was Super Bronsted Bases, and that the acids were actually made from a battery making company. If I were to explain this presentation to a non-science friend, I would say that it was to use stronger acid catalysts which ultimately led to one pot and faster synthesis of complex molecules.

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Hisashi Yamamoto’s presentation on Thursday, October 29 was pretty easy to follow and understandable. Professor Yamamoto is apparently a very famous organic chemist and is a professor at the University of Chicago. He is Japanese, and since he was foreign-born and received his BS from Kyoto University in Japan, I think he still has some accent when he speaks english. However, I did not have any trouble understanding him.

Three new ‘things’ I learned include that 1) cascade reaction is ‘one-pot’ reaction, which synthesizes the complex multinuclear molecules from a single precursor, 2) discovering no side product reaction is important in cascade reaction, because it interferes with the next reaction (goal is to discover 100% atom efficient reaction), and 3) in cascade reactions, various amounts of substrates can produce different products.

Two questions I had during the seminar were 1) How long did you work on this catalyst research for? and 2) How do you figure out which reagent/s to use for the cascade reactions? For the second question, he answered that looking at the previous researches on cascade reactions and knowing the reactivities of each reagents, he can expect which product will be achieved.

I thought the presentation was interesting, because I like organic chemistry the most compared to other science classes, and Professor Yamamoto’s presentation was presented in such a way that undergraduate science major students can easily understand and be interested in his presentation.

I would describe the presentation in one short sentence so my ‘non-science’ friend or family could understand it as this way: “Interesting presentation by the world-famous organic chemist, Professor Yamamoto’s presentation was about cascade reactions.”

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Hisashu Yamamoto, currently Professor of Chemistry at the University of Chicago, is the most influential chemist I have seen in person.  Even as a young man Yamamoto has never wanted to do anything other than Chemistry,  in fact he  had read several university chemistry textbooks before graduating from high school! He has since then dedicated his career to organic chemistry and has seen the proliferate results of his dedication to the field. I could write my entire blog on his accomplishments and still not have covered them all; however, what I was most impressed with was his humbleness, not once did he seem to boast about his achievements or treat us in a way that made us seem less important than his other lecture audiences. I am not a big fan of clichés but the only way to truly describe his presentation style is by the three C’s: cool, calm, and collected.

Yamamoto’s presentation was about designing asymmetric catalysis that would be utilized in a cascade reaction for polyketide synthesis.  The transition from multiple step reactions to cascade ones are becoming more and more evident in organic chemistry.  Although there are some disadvantages, such as losing as much as 50% of the materials to waste, the efficiency of moving from a 15-20 step process, which could take over a month, to synthesis just one molecule,verses one day, by far outweighs the negative aspects of the experiment.  Not only are cascade reactions efficient, but they are (everyone’s favorite) cost effective as well. Imagine how much cheaper drugs could be if they were all done in cascade reaction.  I’m sure the pharmaceutical industry has taken note of this and it probably won’t be long before all the synthetic organic chemists will be shifting from condensing reactions to 2 or 3 step reactions to pot reactions if they haven’t already.  All in all, it is evident that cascade reactions are “green” (what every government wants to hear) and are clearly the future of organic chemistry; so I am certain new discoveries with plenty of funding are coming our way.

I learned many things from Yamamoto’s presentation, however a few concept that stick out in my mind are that 1% of polyketides have biological activity, 5x the average for natural products! That acids discovered over 150 years ago for experiments are still being used today, and the importance that super Bronstead  acids play in chemistry today. If I could go back, I’d ask professor Yamamoto where he sees cascade reactions bringing us in 20 years. And then I wonder when one pot reactions do become dominate, if they will decrease the demand for chemists and lab assistants as they could probably be loaded by a machine; thus I guess the question is,  will we eliminate the need for ourselves? This is not to say chemists won’t be needed, but just how many will be?  Only time will tell, and hopefully Jesus will come before then!

Thanks Dr. Yamamoto for visiting us at Andrews University!

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This week’s speaker was Hisashi Yamamoto, from the University of Chicago.  Dr. Murray met Yamamoto at the symposium in Paris last summer.  Yamamoto is known as a world famous organic chemist.  His presentation was on designing asymmetric catalysis for polyketide synthesis.  Cascade, or “one-pot” reactions are used to make polyketides.  Cascade reactions have been known to reduce the number of steps that a reaction requires, saving both time and material.  These reactions also give no side products and are 100% atom efficient.  Only 1% of polyketides are biologically active and require more than 50 steps to make.

The Mukaiyama aldol reaction is an important reaction for polyketide synthesis.  Very strong acid catalysts, called super Bronsted acids, were needed for this reaction to work.  Triflimide can create an immortal catalyst system.  Chiral phosphoric acid catalysts were investigated.  Acids with selenium were more acidic than acids with sulfur or oxygen.  If the acid catalyst is strong enough, the reaction can be done in water.

A super silyl (TTMSS) group needed to be used in place of a silyl (TMS) group.  Super silyl groups are protecting groups.  They provide a great steric effect, but since they have high HOMO levels, they are also very reactive.  Super silyl makes enolates and cations more reactive, and it provides sufficient reactivity of silyl enol ether.  When super silyl groups react with aldehyde, aldols are produced.  The number of aldols produced depends on the equivalents of super silyl used.  Super silyl provides for very high diastereoselectivity and high yield.  The selectivity tends to be of the syn configuration.  To change the stereochemistry of the product, the stereochemistry of the super silyl group needs to be changed.

Yamamoto’s presentation was heavy on organic chemistry content, and he received a lot of questions at the end.  Yamamoto answered those questions well.  However, the presentation was uninteresting for me.  I had difficulty seeing how all the different reactions came together.  I also did not understand what polyketides could be used for.  If someone is going through all of these organic reactions to make a polyketide, I want to know the purpose of the polyketide.  If only 1% of polyketides are biologically active, what biological activity do the polyketides carry out?  I would also like to know what is meant by “immortal catalyst system.”  It is a term I have never heard before.

Finally, I would like to know if super Bronsted acids are useful in other organic reactions besides the Mukaiyama aldol reaction.  The presentation was difficult to understand at times, but any organic chemist would have loved Yamamoto’s presentation.  If I had to sum up the presentation for a layperson, I would say that polyketides were being made using economical and fast reactions.

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On October 29, 2009 Dr. Hisashi Yamamoto, came to Andrews University from The University of Chicago where he first started working in 2002 as a Distinguished Service Professor.  In 1977 Yamamoto became an Associate Professor of Chemistry at the University of Hawaii.  Then in 1980 he moved ot Nagoya University where he became Professor in 1983.  His specific position at The University of Chicago is Arthur Holly Compton Distinguished Service Professor.

Today’s topic was focused on acid catalysis and the synthesis of these catalysis.  Yamamoto made it very clear that in order for the organic reactions to take place that a person needs to use strong acid catalysts to get the synthesis to react.  A catalyst is a something that you would add to a solution to get the reaction.  More specifically it lowers the activation energy of the solution so that the reaction will take place.  Yamamoto’s goal was to create a cascade reaction where there are no side reactions and a very reactive catalyst so that the process is extremely fast and efficient.  So in order to do this Yamamoto created a Super Bronsted Acid which allowed him to make these reactions take place by eliminating 15 steps to the procedure making the abilities to do the reaction more often and with more ease.  This super Bronsted Acid Catalyst was first created by the Lithium battery company.

Over all it was a very informative talk.  However, I found it hard to understand what he had to say often due to his accent.  The other thing that I noticed was that he seemed to speak extremely quiet so at times I found myself not listening because I couldn’t really hear what he was saying.  On a more positive note he is extremely knowledgable about the topic he presented and was also very polite and kind during the question and answer period.  I also felt like he did not completely answer the questions that were asked of him directly. I felt like he was “beating around the bush” or avoiding the questions a little.  He gave good information about other topics while answering but it did not seem like he actually answered the questions.

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Today the world famous chemist Hisashi Yamamoto spoke about “Designing Asymmetric Catalysis – Cascade Reaction for Polyketide Synthesis”. He is currently working at the University of Chicago as an Arthur Holly Compton Distinguished Service Professor.

A pretty impressive thing that Dr. Murray mentioned at the beginning of the seminar is that Dr. Yamamoto has always wanted to be a chemist. When he was still in high school he read a couple different college chemistry books, mostly organic I believe, and he new from then on that this was the career that he wanted to pursue.

A couple new things that I learned in this seminar is that acid catalysts are some of the oldest catalysts and are still in much use today because of their effectiveness. The research that Dr. Yamamoto is involved in is finding ways to make acid catalysts better, and reduce the number of steps involved in some synthesis reactions. As they are looking for ways to reduce the number of steps involved, they are also trying to minimize the side products that are produced. This is because side products interfere further down the reaction line and they are kind of useless in many cases. This seminar was interesting; Dr. Yamamoto was easy to listen to. Towards the end however, some of the reactions were a little harder to understand. I would explain this seminar to a non-chemistry person as finding ways to speed up reactions while also looking for ways to make the products in fewer steps.

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Chemistry Seminar on October 29, 2009 was given by Dr. Hisashi Yamamoto from the University of Chicago. Dr. Yamamoto is well known in the chemistry world for his accomplishments in organic chemistry. He has over fifty patents and many documents and reviews that have been published. In this seminar Dr. Yamamoto described cascade reactions. The seminar had an abundant amount of information and was well presented.

From this seminar I learned that two important factors for a cascade reaction are no side product reactions and a very reactive catalyst. It is important to have no side product reactions because they would cause interference in reactions to follow. A very reactive catalyst is one in which there is one catalyst in a thousand parts in a reaction. If a molecule has three chirality centers it means that eight isomers can be generated. In the cascade reactions Dr. Yamamoto is using super-Bronsted acids.

Dr. Yamamoto further proved to me that chemistry is much like the rest of our society, we are always trying to make things better and faster than they are currently. Cascade reactions are one-pot reactions that reduce the steps and reagents needed to make a product. This allows the new and improved reactions to produce the same product in around thirty minutes instead of days or months. The biggest disadvantage to this type of synthesis is the amount of waste produced. As an example you may save yourself fifteen steps but create a product that has fifty percent waste.

To describe this seminar to family members and friends I would say that Dr. Yamamoto described how to reduce the steps to a product through a cascade reaction.

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