The correct answer is E.

The synthesis of cyclopropane via addition to the double bond in an alkene is accomplished by reaction with methylene, H₂C:, an example of a class of compounds known as carbenes in which carbon forms two single bonds to make a neutral molecule. (Notice the lone pair of electrons on the carbon atom.) This reactive intermediate is most commonly formed by the heat- or light-induced decomposition of diazomethane, as shown in choice E. The lone pair of electrons on the carbene intermediate are used together with the electrons of the alkene to form the two new single bonds in the cyclopropane product. (An alternative route to cyclopropane synthesis involves reacting diiodomethane and a zinc-copper couple to generate a carbene-like species called a carbenoid which will add a methylene group to the double bond.)

(A) Distortion. This will not produce the desired product.

(B) Distortion. This will not produce the desired product.

(C) Distortion. These reactants will produce an addition with a methoxy group attaching to the second or third carbon.

(D) Distortion. This will not produce the desired product.