EAS: Retrosynthesis

Concept: Concept: Aromatic synthesis starting with benzene/benzene derivatives

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Video Transcript

All right guys, so now we're going to get some practice with proposing aromatic synthesis. So at some point in your course work you're going to be asked to propose an aromatic synthesis starting only from benzene or other benzene derivatives. You're going to have to turn that benzene into something more complicated.
In order to make this work, you're going to have to use your knowledge of sequence groups so that you can add the groups in the right positions. It's never going to be that easy that you don't need to use sequence groups.
Let's do this first example kind of as a worked example where I'm going to give you some hints and the second one you'll be completely on your own. For this first one, it says synthesize the target molecule from acetophenone and any other reagents. In this case, acetophenone is given to you as the molecule. But, you should be aware of what the name acetophenone means from the naming benzene area of our Clutch videos.
So what's going on here? What are the different transformations that are taking place? One thing that's happening is that I have a ketone that at some point needs to become a benzoic acid. So that's interesting. I've also got to add a nitro group in the para position so that's p, para substitution. So there's kind of a lot going on here. I've got a few different things.
One thing that I know for sure is that to put a nitro into the para position, at some point, my ketone is going to have to become what? An ortho, para director. Right now what type of director is it? Meta. Right now this is a meta director. If I were to nitrate this ketone right now, or this acetophenone, I would actually get a nitro here. Is that right? No. So I'm going to have to use my knowledge of sequence groups to figure out how can I turn that into an ortho, para director.
Now benzoic acid. Is this an ortho, para director? No, this is also a meta director. That means that I have to turn this into a benzoic acid sometime after I've added the nitro group because if I just turn it straight into benzoic acid, then I'm going to get a meta nitro group again. So this is kind of already outlining all the things we need to do.
So now I'm going to let you guys get creative. This is the part that I can't do for you. You just have to get creative with all the reactions we've learned and see if you can figure out the right sequence of reagents to make this final product. So go ahead and try your best and then I'll answer it for you. 

Concept: Example 1: Synthesize the target molecule

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Concept: Example 2: Synthesize the target molecule

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EAS: Retrosynthesis Additional Practice Problems

Propose a synthesis of compound B starting from benzene and acetyl chloride (CH3COCl ) as the only sources of carbon. Several steps may be required. Assume that all reagents needed for the synthesis are available. Indicate clearly the reagents used and the products obtained after each step. Mechanisms are not required.

 

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For the reaction below, draw the structure of the appropriate compound in the box. Indicate stereochemistry where it is pertinent. For Friedel Crafts reactions, assume that the major product is the least sterically hindered one.

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Using any necessary reagents, show how you would accomplish the following transformations.

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Perform a retrosynthetic analysis on the molecules below (work backwards) from the given commercially available starting materials.

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Provide the reagents to accomplish the transformation below. More than one step might be required for the transformation. 

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Which is the best method for carrying out the following reaction?

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Provide stepwise synthesis for the following transformation:

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Propose the sythetic plan complete with reagents and proper order of reactions. You must show the product of each step in your scheme, however no detailed mechanism is required. 

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Circle the stating material for the following synthetic sequence.

 

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Which sequence of reactions would give (some of) the correct product? 

1) A and B

2) A and C

3) B and C

4) B only

5) A, B, and C 

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Which sets of reagents would best be used to perform the following reaction?

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Provide a scheme for the synthesis of the molecule below, using the indicated starting material and reagents of your choice.

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Propose a multi-step synthetic scheme complete with reagents and proper order of reactions (no mechanisms required) for the following molecule starting from the indicated compounds. You may use any reagents neccessary. Show the product of each step in your scheme.

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The following synthetic pathway does NOT sufficiently produce the indicated product. Provide an acceptable synthetic pathway. 

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Predict the major product for each of the following reactions paying attention to the region- and stereochemistry. If there is no reaction, write just “No Reaction.”

 

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Using any necessary reagents, show how you would accomplish the following transformations.

 

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Which set of reagents will best accomplish this transformation?

 

 

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