diyne+diol





Jimmy : This is a good synthetic route to the diketone the rest is quite simple, as Tim has shown below. If you supply the reterosynthesis and description, and complete the scheme this will be a complete post.

Jimmy Metellus (Complete)

For this synthesis I mostly used the power point notes of Chapter 9 and the wade text book for research components (CH. 9-5 and up). As shown in my synthesis I clearly showed what I was using. The logic behind the synthesis is simple and shown below. First i added acetylene and sodium amine, than I added methyl bromine to add a methyl to it and I repeated it one more time to add another methyl. Then dilkMN04 was added to cause the formation of 4 hydroxyl. Than -2h20 was added in order to make d-diketone. Ethelyne sodium is then added to break the double bond with oxygen to cause a triple bond to be made.

Jimmy: The synthesis looks complete Just include a discussion and reterosynthesis. Take a look at what Tim has done below. Bruce Bondurant This looks good

Below post by Tim Maynard (20 April 11)

After reviewing the chapter on Alkynes, I determined that two simple processes could be used to synthesis 3,4-dimethylhexa-1,5-diyne-3,4-diol. The process of alkylation of acetylide ions along with oxidation to alpha-diketones would accomplish this task. Through a retrosynthetic analysis, the last process should be adding the triple bond alkyne groups to the carbon chain. Prior to that the carbonyl groups should be added to the base carbon chain. The first two steps should be expanding the base acetylene through alkylation substitution. It is important to create the necessary methyl groups prior to focusing on the functional groups that are easier to create from the base alkyne triple bond.



My synthesis is along the same lines as the techniques used by Jimmy above. Although I was able to find a couple other processes, the principles used in this synthesis are straight from Wade Ch 9 sections 9-6, 9-7A, and 9-10A and are great applications of the alkyne chemistry that we learned. The first step of creating the acetylide anions takes advantage of the unique acidic properties of the terminal alkyne hydrogen through the use of the strong base Sodium Amide. Once in its anionic form, acetylde anion can lengthen carbon chains by attacking alkyl halides as long as they are primary halides. By repeating this process a second time with methyl iodide, the synthesis forms the but-2-yne from which the functional groups are added. The first set of functional groups added are the carbonyl groups by oxidizing the triple bond using cold, dilute neutral solution of Potassium Permanganate. This creates the compound 2,3-butanedione also known as diacetyl. Throughout my research I found out that diacetyl is actually a by-product of alcohol fermentation. I have included a .pdf of a research paper on the production of diacetyl in fermentation. It is very interesting and explains the enzymic reactions with yeast and what occurs throughout the process. Diacetyl actually contributes to the taste of butter and gives beer the slipperiness feel to it and contributes to its taste as well. Back to the reaction, after 2,3-butanedione is formed, the final step of adding the two acetylenes is accomplished by attacking the carbonyl carbons with acetylide anions. This creates the sigma bond connecting the acetylenes as well as breaking the oxygen double bonds to create the alkoxides. Water or dilute acid protonates the alkoxide and the final product is complete. Also, because I found the diacetyl production in fermentation so interesting, I did some research on the feasibility of separating the diacetyl from the fermentation process and I found out a couple of things. First, fractionally distilling the diacetyl out of the brew would be difficult because its boiling point (88° C) is right in between the water (100° C) and ethanol (78° C). Secondly, some people used adsorbents like silica gel, activated charcoal, etc. to bind the diacetyl out of the brew, but it had adverse effects on the taste and quality of the brew and was deemed not useful. So basically, unless Dr. Bondurant can help me come up with an effective way of separating diacetyl during fermentation, then this will not be an effective way to help me make 3,4-dimethylhexa-1,5-diyne-3,4-diol.

1) L.G. Wade Jr. __Organic Chemistry__ 7th edition. (Upper saddle River New York Pearson/Prentice Hall 2010)

2) Wikipedia. Diacetyl. []

Tim: You have a nice synthetic plan here, and a good description of it. The only thing that you need to do is provide a retero synthesis. Basicly just go backwords from the product to the reactants with arrows that look like this. => and no reagents. I think you can extract the diketone from a fermentation solution by using latex beads that have been substituted with an amine. It is also available from Sigma Aldrich, but, of course, it is a 4 carbon compound.

Post Updated by Tim Maynard (16 Apr 11)

Tim: This is good Bruce Bondurant



When I first thought of this mechanism, I was thinking of the above reactions, but thought we needed some differentiation, so I decided to look up a different mechanism. I found the Wurtz reaction and thought it seemed plausible. Acetyl bromide is prepared from PBr3 and acetic acid. Then, 2,3-butanedione is formed from symmetric coupling of acetyl bromide via the Wurtz reaction. Sodium acetylide is prepared via sodium amide. Then, sodium acetylide reacts with 2,3-butanedione to form the product. []

Julian: You sent me to the literature with this one. I had completely forgotten about the Wurtz reaction. I looked it up, and found that the reaction with sodium as the metal works with alkyl, aryl and vinyl halides but not with acyl halides. I looked in March Advanced Organic (on reserve at the DM library) and found that the reaction can work with acyl halides if you use nanoparticulate lead (also called pyrophoric lead) This is the reference from March Jerry March,__Advanced Organic Chemistry__ Fourth Edition Wiley and sons 1992 page 490 (reaction 0106) March also references Han and Boudjouk, //Tetrahedron letters// **1981,** 22, page 2757. If you make this change of reagents and supply a reterosynthesis (see my comments to Tim above) This will be a complete and very ingenious post. Thank you for reminding me of my organometalic chemistry. PS, be careful when you upload files. If you have another person’s work selected, it will delete their post. Bruce Bondurant Julian: his route is good. I really appreciate the fact that you sought out a unique syntheses. and researched a reaction that we did not even study in class. nice work. Bruce bondurant