Question

What would be the product if dimethyl maleate was heated in the presence of 3-sulfolene?

Answer 1

An organic reaction between a substituted alkene and a conjugated diene to form a substituted cyclohexene derivative is said to be Diels-Alder reaction (specifically, [4+2 cycloaddition). The formation of new $\sigma$-bonds is the driving force of this reaction, which is energetically more stable than the $\pi$-bonds.

The reaction that takes place due to the heating of dimethyl maleate in presence of 3-sulfolene is as shown in the image.

On heating 3-sulfolene the compound breaks down to give sulfur dioxide gas and butadiene. This diene then reacts with dimethyl maleate which acts as a dienophiles and then these two diene and dienophiles will undergo a Diels-Alder reaction to form a new 6-membered cyclohexene ring.

Thus, the product formed due to the heating of dimethyl maleate in presence of 3-sulfolene is dimethyl cyclohex-4-ene-1,2-dicarboxylate.