Question

Draw a stepwise mechanism for the following reaction that converts a dicarbonyl compoundto a furan.

Short answer

Stepwise reactions consist of several intermediates and steps. They are also termed multiple-step reactions.

Step-by-step solution

Stepwise reactions

Stepwise reactions consist of several intermediates and steps. They are also termed multiple-step reactions.

Reaction of carbonyl compound

Nucleophilic addition reactions happen faster when the carbonyl carbon is electrophilic. Acid-catalyzed reactions make the carbonyl carbon electrophilic to proceed for nucleophilic attack.

An acid-catalyzed reaction can transform an alcohol group into a good leaving group.

Mechanism for the conversion of dicarbonyl compound to furan

The carbonyl oxygen gets protonated in the first step leading to the formation of oxonium ion. The second step involves the abstraction of a proton from the electron-deficient carbon leading to the formation of an enolate ion.

The third step is the nucleophilic attack of the oxygen ion on the oxonium ion.

The next step involves the protonation of the OH group converting it to a good leaving group. The last step is the proton abstraction by a base that leads to the formation of the desired product. The mechanism can be given as:

Conversion of dicarbonyl compound to furan