Provide a general principle that may be utilized in anticipating the main product of a Diels-Alder reaction involving an alkene that has a substituent that can withdraw electrons and a diene that has a substituent that, based on its placement, can donate electrons through resonance.

• A. If the electron-donating group is attached at either the end or not the end of the diene, both will be adjacent to the electron-withdrawing group of the dienophile in the product.
• B. If the electron-donating group is attached at either the end or not the end of the diene, both will be opposite to the electron-withdrawing group of the dienophile in the product.
• C. If the electron-donating group is attached at the end of the diene, it will be adjacent to the electron-withdrawing group of the dienophile in the product, while if it is not attached at the end of the diene, it will be at the opposite to the electron-withdrawing group of the dienophile in the product.
• D. If the electron-donating group is attached at the end of the diene, it will be opposite to the electron-withdrawing group of the dienophile in the product, while if it is not attached at the end of the diene, it will be adjacent to the electron-withdrawing group of the dienophile in the product.

Answer: (C)