Suggest a synthesis for the following molecules beginning with...

Question

Suggest a synthesis for the following molecules beginning with organic molecules containing three or fewer carbons. [You will need to use a protecting group in these syntheses.]

(b) Chemical structure of 4-hydroxybut-2-ynal, featuring an aldehyde group and a terminal hydroxyl group.

Accepted Answer

All right. Hi, everyone. So this question is asking us, how would you synthesize the given compound using organic molecules with no more than three carbons and an alcohol protecting group. Now, the product in question is hexane 13 dial. So what I'm going to do first is I'm going to label all six carbons of my parent chain. And here, right, notice how the question is telling us to use molecules with no more than three carbons to make our end product. So essentially, right, for this question, what we can do is combine two organic molecules that have three carbons each. So in this case, right, recall that one thing we can do is alate an aldehyde using a greeny region. Because if I separate carbons three and four of the parent chain, I end up with an O group, a three carbon al group, which recall can come from a ringer region, right? So if I go ahead and I make the hydroxy group of carbon three an aldehyde, instead I end up with a hydroxy aldehyde. And I can go ahead and combine that with a greener reagent with the green good reagent. Having to be three carbons long. So something like propal magnesium bromide. Now we have the pieces, right. But the problem is the hydroxy group in our hydroxy aldehyde because recall that the proton of my alcohol here is acidic. So therefore, the green mere agent would react with the hydroxy proton instead of reacting with the carbon. So the first thing we have to do, right is we have to protect that alcohol to make sure that my green good re agent is not going to react with it because the idea here is to prevent any unwanted side reactions, right? So if I start off with my three hydroxy propanol, the first thing we have to do is protect the hydroxy group and prevent further reaction. Right now, rao silo ethers are excellent protecting groups for alcohol and one silo ether that we can use, right, is try isopropyl silo chloride or oops or T IP SCL. But in addition to reacting my hydroxy group here with T IP SCL recall that we have to use a weak base such as triamine in order to facilitate the removal of the hydroxy proton, right. So once that happens here is my aldehyde that's not reacting quite yet. But now that we're reacting with the protecting group eight, the hydroxy proton is replaced by a bond between oxygen and silicon. And since we're dealing with try isopropyl silo chloride, that silicone atom was bound to three isopropyl groups. So now, now that my hydroxy group has been protected, right. My silo ether is not going to react with my Green yard re agent instead. What we've done here is guarantee that the greener re agent is going to react with my car bottle instead. So first we're going to add propo magnesium Promide so that it can react with my car bono here and extend the carbon chain by three carbons. But then right, that's going to yield an oxide ion because recall that the carbon of the Green yard reagent attacks the carbon and displaces the pi bo of the carbona leaving oxygen with a negative charge. So the second step of the green good reaction itself has to be the addition of water in order to proton the Aloxi ion and yield a secondary alcohol. So here we have a six carbon chain because we've combined together two organic molecules that have three carbons each. So we have six carbons with my silo ether at the end here and now I have a secondary alcohol. So now that I have my secondary alcohol, right, my silo ether has run its course, it's done its job. So our last step is going to be our detection or our removal of that silo ether protecting group. No recall here, right, that silo ethers can be removed using a fluoride salt such as fe tribute ammonium fluoride. So in this case, right, what we do in the detection step is we react our silo ether with te tribute ammonium fluoride in the presence of water because that is going to remove my silo ether and replace it with my hydroxy group once again. So now I end up with my dial and there you have it. So in this case, what we did here, right was we underwent a green yard reagent using a hydroxy alcohol because we had to extend the carbon chain to give six carbons in total. But due to the presence of a hydroxy group, we had to protect it. First and foremost, in order to make sure that the green reagent reacts with the carbon of the aldehyde and not the hydroxy group itself. And then after carrying out the greener reaction, we had to detect or remove the silo ether from our product to yield a dial at the very end of the process. So with that being said, if you stuck around to the end, thank you so much for watching. And I hope you found this helpful.

Suggest a synthesis for the following molecules beginning with organic molecules containing three or fewer carbons. [You will need to use a protecting group in these syntheses.]
(b)

Key Concepts

Synthesis Strategy

Protecting Groups

Functional Group Interconversion

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