[limonade]

Does this synthesis look like it would follow through alright?
Sorry if the picture is a tad blurry. My webcam isn't so good.

I am only supposed to use cyclopentane and acetylene as my source of carbon atoms. Please let me know if it looks plausible.

The little box in the corner is just how I used acetylene with an addition of HBr and then treated with Li  NH3 to get ethyl bromide for use in the ether synthesis last step.

Thanks for your help.

[magician4]

in my opinion:

line # 4 would gain you an alcohol from "hydroboration followed by oxidative workup"  (instead of an enol , like in your proposal. besides: enoles almost always will show  keto-enol - rearrangement instantly)

this might be usefull nevertheless


regards

Ingo

[mjpam]

I have similar questions to magician4 on your reduction of the alkyne to the alkene.

If I'm reding the the scheme correctly, you have a two-step reduction taking place:

• the alkyne is reduced to an alkene with lithium in liquid ammonia
• the alkene undergoes hydroboration to a secondary alcohol

I am unclear on (2) because both the reactant and the product are alkenes, and the stereochemistry as drawn is slightly confusing. In hydroboration, the borane adduct/derivative (BA/D) adds syn to the multiple bond, and the hydride in the BA/D, due to steric hinderence on the more highly substituted, adds in the anti-Markovnikov orientation. Thus, while there is relatively free rotation around a substituted single bond in an alkane, it would be helpful to show that you understand the the mechanistic reasons for the stereospecificity of hydroboration if you either drew the hydrogen and the hydoxyl on the same side of the single bond or indicated the absolute stereochemistry with wedge bonds.

[limonade]

Thank you for your response. You are right. I should have drawn it as an alkane instead of an alkene after the hydroboration, and indicated proper stereochemistry.

[mjpam]

Thank you for your response. You are right. I should have drawn it as an alkane instead of an alkene after the hydroboration, and indicated proper stereochemistry.

Did your professor specify a particular enatiomer or if the product had to be enantiopure?

You may want to reconsider hydroboration. There might be other reactions that don't require a separate ether synthesis step.