Cycloaddition Reactions - Synthesis

Each of the molecules shown on the left can be prepared by a simple [4+2] cycloaddition reaction. For each compound, draw the structure of the diene and dienophile which would be required for the synthesis, paying particular attention to the stereochemistry of the reactants.
Click the mouse on the molecule to view the answer;

click on the arrow for help in visualizing the cycloaddition.

In a [4+2] cycloaddition reaction, new bonds will form between the terminal carbons of the diene and the alkene carbons of the dienophile, as shown below.

In a [4+2] cycloaddition reaction, new bonds will form between the terminal carbons of the diene and the alkene carbons of the dienophile. As shown below, in this problem, it is helpful to first convert the chair cyclohexene into the boat form.

To identify the reactants in a [4+2] cycloaddition reaction, identify the carbons of the dienophile (they will be the two carbons in a six-member ring which are opposite to the double bond in the product) and mentally split the bonds, separating the carbon skeletons of the diene and the dienophile. If you have a choice of two possible dienophiles (as in this problem) select the dienophile with the most electron-withdrawing groups (recall that electron withdrawing groups enhance the reactivity of a dienophile).