Devise a synthesis of each compound from cyclohexene as the starting material. More than one ste

Devise a synthesis of each compound from cyclohexene as the...

Key Concepts

Nucleophilic Ring Opening of Epoxides

Once an epoxide is formed, it serves as an electrophilic intermediate that can be attacked by nucleophiles under acidic or basic conditions. This ring opening reaction is a versatile method to generate a range of products, such as diols, halohydrins, or ethers, by introducing different nucleophiles that determine the regiochemistry and stereochemistry of the final product. It is a key step in designing multi-step syntheses from alkenes.

Hydroboration-Oxidation

Hydroboration-oxidation is a two-step reaction sequence used to convert an alkene into an alcohol with anti-Markovnikov regioselectivity. In the first step, borane adds across the alkene in a syn-addition manner, and then oxidation converts the C–B bond into a C–OH bond. This method is critical for synthesizing alcohols from alkenes when traditional electrophilic hydration might not give the desired regio- or stereochemical outcome.

Alkene Addition Reactions

This concept involves the treatment of alkenes, such as cyclohexene, with electrophiles or nucleophiles to add across the carbon–carbon double bond. It is fundamental for converting a relatively inert alkene into a more reactive functionalized molecule. These reactions underpin many synthetic routes, allowing the installation of functional groups like halogens, hydroxyls, or peroxy groups through electrophilic or anti-electrophilic mechanisms that often follow predictable regiochemistry (e.g., Markovnikov or anti-Markovnikov addition).

Epoxidation of Alkenes

Epoxidation is the transformation of an alkene into an epoxide using an oxidizing agent, typically a peroxy acid. This reaction is a common strategy for introducing an oxygen atom between the carbons of the former double bond, forming a strained three-membered ring. The resultant epoxide is highly reactive and can be further manipulated via ring-opening reactions to install various functional groups in a stereocontrolled manner.

Transcript

00:02 This is the answer to chapter 10, problem number 67, from the smith organic chemistry textbook.

00:10 And this problem asks us to devise a synthesis for each of the products that were given in the problem from the given starting material.

00:20 And it says more than one step is required.

00:23 So each of these is going to be a multi -step problem.

00:26 And so i'm just going to go ahead and get started.

00:31 So for a, we are going to need to proceed through an alkyne intermediate.

00:40 And so one way that we can do that is to use pbr and get to the bromide here and then eliminate the bromide with potassium terpetoxide.

01:04 And that's going to give us the terminal alken.

01:09 And then we can do an acid -catalyzed hydration to add an alcohol in markovnikov fashion.

01:23 So that's going to add the alcohol to the more substituted carbon.

01:28 And there's our product for a.

01:31 Okay, so then for b, we're starting from the bromide.

01:37 And we need to get to the dibromide.

01:39 And so the easiest way to do this is to do an elimination.

01:44 So again, we'll use potassium terpitoxide.

01:48 We'll do this elimination.

01:51 And then we can treat that alkyne that we made with some elemental bromine.

01:59 And that is going to give us the dibromide.

02:05 So there we go, di bromide.

02:08 So that's b.

02:09 So then for c, we're going to say.

02:11 Start with an elimination again.

02:13 However, in this case, we have an alcohol instead of an alkali.

02:21 And so in order to affect an elimination, we're going to have to use concentrated sulfuric acid and some heat.

02:31 And that's going to get us to this same intermediate that we had in b.

02:38 And so now we need to make a term.

02:44 Terminal methyl ether from this.

02:47 And so what we can do is a hydroboration oxidation.

03:00 And the purpose of the hydroboration oxidation is going to be to add a terminal alcohol here.

03:07 So remember that's an anti -marcoffinikov addition of an alcohol.

03:11 And so now we can treat this with a strong base like sodium hydride, followed by methyl iodide...

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