# Cis Orientation of dienophiles orientation of groups maintained in Diels Alder

When I was reading about Diels-Alder reactions, I was confused about the cis and trans rules for dienophiles, as shown below.

The text told me that "a cis dienophile will generate a ring with cis substitution, and trans dienophiles will generate a ring with trans substitution."

I'm a bit confused.

Why is this the case?

• either you start with a (trans)-configurated diene, as in the first example drawn by you. Since the Diels-Alder simultaneously forms the new $$\sigma$$-bonds on the expense of $$\pi$$-bonds and moves the location of the remaining double bond, the substitutents R are either both below, or both above this reference plane. Relatively to each other, these substitutents R in the product conserved their (cis)-relationship from the dienophile.