How might you synthesize each of the following compounds using an aldol reaction? Show the struc

How might you synthesize each of the following compounds...

Key Concepts

Aldol Reaction Mechanism

The aldol reaction involves the formation of a carbon–carbon bond between two carbonyl compounds. In this reaction, an enolate ion, generated from an aldehyde or ketone under basic or acidic conditions, acts as a nucleophile and attacks another carbonyl compound. The initial product is a ??hydroxy carbonyl compound, known as an aldol, which can then undergo dehydration to form an ?,??unsaturated carbonyl compound in aldol condensation processes.

Enolate Formation

Enolate formation is a critical step in the aldol reaction. Under basic conditions, a base abstracts an ??hydrogen from a carbonyl compound, producing a resonance-stabilized enolate ion. This enolate is the nucleophilic species that subsequently adds to the electrophilic carbonyl carbon of another molecule, setting the stage for the aldol addition.

Cross-Aldol Reaction

In cross-aldol reactions, two different carbonyl compounds are used to form the aldol product. Selectivity is key, as one must control which compound forms the enolate and which serves as the electrophile, often by choosing a carbonyl component without ??hydrogens or adjusting the reaction stoichiometry. This strategic selection minimizes self-condensation and favors the formation of the desired product.

Strategic Selection of Starting Materials

The design of an aldol synthesis involves choosing appropriate aldehydes and ketones such that one or both can form an enolate and react efficiently with the other. Factors such as the presence of ??hydrogens, steric hindrance, and electronic effects dictate which reagent serves as the nucleophilic enolate donor and which as the electrophilic acceptor, ultimately impacting the structure and stereochemistry of the product.

Transcript

00:01 Okay, this problem is asking us how do we make these compounds from an aldol condensation? so what i'm given is i'm given a benzene first, connected to an eventual alken, connected to carbonil, and then same thing, benzene on this side.

00:15 Okay, so how do we make this compound using reactants in an aldol condensation? luckily for al -dall condensations, i have a trick, and my trick is as follows.

00:24 First up, we locate the position of my alpha -beta unsaturated system.

00:30 We make sure that we do in fact have one.

00:32 Because in all -dall condensation reactions, we have the addition of an alpha -beta -unsaturated system, characterized by the carbonyl, and then my al -keen in the alpha -beta position.

00:43 Okay, so that's my alpha -beta -unshaturated system.

00:45 Next up, i locate my al -keen.

00:48 So this is my al -keen.

00:50 Once i locate my al -keen, i identified the carbon that is closest to my, that is not representative of induction.

00:58 I locate the carbon that is closest to my carbonyl.

01:02 So this carbonyl, this carbon is closest to it.

01:05 So once i identify that, i draw a squiggly line down that carbon, ensuring that i have nothing attached to this side of my alkyne.

01:14 So here's my alkyne, i have nothing attached to this side of it.

01:17 Okay, so once i draw that squiggly line, then i proceed.

01:21 That squiggly line is representative of a breaking of bonds.

01:25 Okay, so i'm just going to break that bond like this.

01:30 Like that, and then i have on the other side the remainder of my compound.

01:36 Okay, so this is obviously in the mechanism we're not breaking that bond, or we're not adding this alken to right here.

01:44 We're doing, in fact, something completely different, but this is just for the trick.

01:48 And then for the trick, once i locate, or once i make this compound, the one that has the alken, all i have to do is add an oxygen, where it was connected to this carbon.

01:59 Okay, so that is my, those are the reactions.

02:01 That's what i have.

02:03 I have a benzaldehyde reacting with this compound right there.

02:07 Okay, so they're not necessarily the same.

02:10 Okay, next up, i have this.

02:13 I'm given cyclopentine like that, and then i have connected to it a ketone.

02:23 Okay, so how do we make this molecule? well, same thing as before.

02:27 First up, i make sure that i do, in fact, have my alpha -beta unsaturated system.

02:31 And in this case, i do, because i have my carbonyl, and then in the alpha -beta, beta position, i have my alken.

02:39 Okay, so once i identify that i do have those things, i locate my alken, and then i locate the carbon that is closest to my carbonyl.

02:47 Okay, so here's my carbonyl, here is my carbon that is closest to it, and then i draw a squiggly line to ensure that nothing is attached to this alken.

02:57 So i make sure that nothing is attached to this side of my alken.

03:01 All i would have, if i are to separate this, would be hydrogens.

03:06 So that might be a little bit confusing, but all i would have to do is stretch this molecule out, represented by the breaking of this bond.

03:13 Okay, so i would have this.

03:16 Oops, i won't draw that oxen yet.

03:18 I have that, and then i have this, this, this, that.

03:21 And then, of course, i don't have this bond any longer, so i would have had to draw this like this, like that.

03:30 But i'm breaking this bond, so i don't have that any longer.

03:34 So instead, i just have this.

03:40 Okay, so that is where i'm at right now.

03:42 And then, of course, all i have to do is add my oxygen to the former bond between this alkyene and this carbon.

03:50 Okay, and then that's, i'm done with that.

03:51 Okay, that's why i started with.

03:53 Okay, that would undergo an aldol condensation to result in this product.

03:58 Okay, next up, i have this one, in which i'm given a benzene, and then attached to that benzene, i have a cyclopentine like that, and then attached to that, i have my alvehyde...

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