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
The acetoacetic ester synthesis is a useful synthetic tool for preparing ketones having one or two alkyl groups on the ɑ position: At first, this may look confusing since there is a whole ester group being lost in … Read more
We have seen, in the alpha halogenation and aldol condensation reactions, that enolates are good nucleophiles capable of attacking halogens and carbonyl groups. In addition to these, enolates can also be alkylated when reacted with alkyl halides via SN2 mechanism: … Read more
If a compound has two carbonyl groups (dicarbonyl compound), it undergoes an intramolecular aldol reaction if a five- or six-membered ring can be formed: What happens is one of the carbonyls is deprotonated at the ɑ position, thus … Read more
Carboxylic acids with α hydrogen atoms can be brominated in the presence of catalytic amounts of phosphorus (or a phosphorus tribromide) forming α-bromo carboxylic acids. This is known as the Hell–Volhard–Zelinski (or HVZ) reaction: Now, let’s understand how … Read more
All the aldol reactions we discussed so far were between identical partners, meaning the same carbonyl compound served as an electrophile and a nucleophile in the form of an enolate: An aldol reaction between two different carbonyl compounds … Read more
We have seen that the product of the aldol reaction is a β-hydroxy carbonyl compound: One can look at it as an alcohol, and what is interesting about this alcohol is that it undergoes an elimination when heated … Read more
