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Need assistance on a synthesis question for Organic Chem 2

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dday88:
First time poster and second year of organic chemistry student here, having a bit of trouble with a synthesis question on our quizzes. The question is pretty straightforward but I know it involves a number of steps. this gyazo screencap shows the reaction i need to complete https://gyazo.com/7ef755abab90690da2b6e6d6c7960591

(mod edit in structures - from to +/- )

I’m thinking the first step would be to treat the cyclopentene with NBS. After attaching the Bromine I would then add Mg to the solution to create a Grignard, add the chain and then epoxidize. My synthesis falls short when I try to get the stereochemistry correct. The Grignard chain scrambles the sterochemistry somewhere in this sysnthesis and I can’t figure out how. Also the elimination of the double bond, and addition of the secondary alcohol group should come after the Grignard reaction right? Thank you all in advance for your responses!!

spirochete:
You could open up an epoxide with an organometallic. That would create a trans product.

kriggy:

--- Quote from: dday88 on March 18, 2019, 07:19:40 PM ---
I’m thinking the first step would be to treat the cyclopentene with NBS. After attaching the Bromine I would then add Mg to the solution to create a Grignard, add the chain and then epoxidize. My synthesis falls short when I try to get the stereochemistry correct. The Grignard chain scrambles the sterochemistry somewhere in this sysnthesis and I can’t figure out how. Also the elimination of the double bond, and addition of the secondary alcohol group should come after the Grignard reaction right? Thank you all in advance for your responses!!

--- End quote ---

Please next time, show us a scheme of your proposed reaction, its way easier to get it from drawing than vocal description.

Anyway, think about this: your product synthesis is (obviously/quite likely) multiple steps. Which step do you think will be performed last? Try to start from the product and get to required starting material using known reactions. Also, im not sure if you have to make it enantiopure or not but since its OC2, im assuming you should only care about the trans-relationship between the two substituents

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