We have seen, in different reactions such as the aldol condensation, alkylation, and alpha halogenation, that enolates are very good nucleophiles capable of attacking electrophilic centers. Interestingly, the halogenation of aldehydes and ketones at the alpha position works with both acid … Read more
In the previous post, we talked about the aldol reaction, which occurs when an aldehyde is treated with a base. The role of the base here is to deprotonate the ɑ position of the aldehyde and thus convert it into … Read more
We know that base-catalyzed halogenation of aldehydes and ketones replaces all the ɑ hydrogens: The reaction is difficult to stop at monohalogenation because the product, after the first step, is more reactive than the starting carbonyl, and therefore keeps … Read more
We talked about the Michael reaction in which the nucleophile is a doubly stabilized enolate performing a conjugate (1, 4) addition: Remember, at the same time, that regular enolates are not efficient Michael donors since they are stronger … Read more
A Claisen condensation between two different esters is called a crossed Claisen condensation. There are two main types of crossed Claisen that we will go over in this post. One is the reaction between esters, both having alpha hydrogens, and … Read more
Just like the aldol reaction, intramolecular Claisen reactions occur when five- or six-membered rings can be formed. These are called the Dieckmann condensation where one ester, of the same molecule, serves as an electrophile and the other is deprotonated and … Read more
We discussed quite extensively the aldol reactions of aldehydes and ketones, which involve enolate ions generated by base-catalysis. Esters are known to undergo an analog reaction called Claisen Condensation since they too have an acidic ɑ position to form an … Read more
In the previous post, we talked about the Michael reaction, which is a conjugate-addition reaction of doubly stabilized enolates such as malonic ester, acetoacetic ester, and the like with ɑ, β-unsaturated carbonyl compounds: One important variation of the … Read more
Michael reactions are conjugate-addition reactions of doubly stabilized enolates such as malonic ester, acetoacetic ester, and the like with ɑ, β-unsaturated carbonyl compounds: So, the Michael reaction is a particular type of conjugate addition reaction that ɑ, β-unsaturated … Read more
In the previous post, we talked about the acetoacetic ester synthesis, which is used for preparing ketones having one or two alkyl groups on the ɑ position: Another way to look at this reaction is to say that … Read more
