Boron Aldol Reaction - Organic Chemistry, Reaction Mechanism

[@nicholasmwanzia776]

Thanks for your wonderful explanation.

[@CasualChemistry]

🙂 Glad you enjoyed the video

[@danielchin9309]

Where were your videos during my undergrad? 😂 Good content, keep it up!

[@CasualChemistry]

Thanks for the feedback and glad you enjoyed the video 🙂

[@Gurdeepsingh-wv5tn]

Very nice explanation. I have one question, if you are taking R group as a iPr, then enolisation occur from other side because, NEt3 is not that much strong and bulky base.

[@CasualChemistry]

The main idea is there has to be a difference between the two sides of the carbonyl do differentiate between. The NEt3 is bulky enough but not too bulky to be able to get the H off the ethyl group but not the isopropyl group just on sterics. This is the dominant thing going on. I’m going to touch on this in my next video: another factor is the isopropyl group’s bulk favours the boron Lewis acid sitting on the ethyl group side. There’s also a Stereoelectronic effect that helps make the ethyl group’s protons a bit more acidic. These reactions are done at low temperatures when you need to be careful to select so small differences in activation energies are enough to get selectivity.

[@sarvanks7711]

Great explanation.

[@CasualChemistry]

Many thanks :). I'll probably do some extension material on this type of aldol topic in the future as there's all sorts of ways of building stereocontrol into these models.

[@sarvanks7711]

@@CasualChemistry Yes, that would be very great for everyone. Please.

[@m.jadidinejad6727]

Very good😊 when I understand problem I bacome very happy

[@CasualChemistry]

🙂

[@amitkumarde9239]

Hlw casual chemistry I love your lecture series. It helps me a lot even at my master's degree. I have a small question in your retrosynthesis series you said that boron enolisation give Z enolate but here E enolate gets formed. Here bulky iso propyl also present.

[@CasualChemistry]

That's great to hear - glad the videos are useful :) I think I've understood which other video your question refers to With the boron-mediated enolisation, it is very dependent on what you choose as the substituents/ligands on the boron centre and what you choose as the base. Hence, this technique is a reagent-controlled enolisation. Although others options exist, two common reliable techniques are: (1) For making Z enolates - use Bu2BOTf and iPrEt2N. This is a small alkyl substituent, a really good leaving group in the triflate, and a slightly bulkier base. (2) For making E enolates - use Cy2BCl and Et3N. This is a bulkier alkyl substituent, a less good leaving group in the chloride, and a slightly smaller base. I should probably get around to making a video lecture of some sort on enolates as I have lots of teaching materials on this topic as it's very close to my PhD work.

[@amitkumarde9239]

@@CasualChemistry that will be great and thank you once again