Cyclic Diene Dienophiles

Cyclic dienes added to alkene dienophiles also lead to two new form of stereoisomeric products, the endo and exo products (Kilway, “Lecture”). In cases where dienes and dienophiles align above one another, the endo product is formed (Hunt). The endo product will have two axial substituent groups (Kilway, “Lecture”). This formation typically forms the major product because it takes less kinetic energy to be formed due to secondary orbital interactions with the substituents in transition states (Hunt). The rule that guides this principle is typically referred to as the “Alder Endo Rule”. In instances where the diene and dienophile are staggered and they must reach for each other in order to form the product, the exo product is formed (Hunt).
Dimethyl acetylenedicarboxylate (0.10 mL, 0.81 mmol) and nitrobenzene (1 mL) were added to to tetraphenylcyclopentadienone (0.103 g, 0.268 mmol) in a small reaction tube with a boiling stick using glass pipettes to form a dark purple soln. The rxn was then lowered into a sand bath and allowed to reflux until color change from dark purple to tan was observed. Upon cooling, ethanol (3 mL) was added and the soln was shaken to facilitate combination. The tan soln was then placed in an ice bath to cool for 10 min. The solvent was removed from the solid under vacuum filtration and washed with cold ethanol to retrieve a white precipitate. The final product, dimethyl tetraphenylphthalate was massed (0.055 g, 0.110 mmol,
A dark purple soln was created from tetraphenylcyclopentadienone (0.506 g, 1.32 mmol) and glyme (3 mL) in a large reaction tube with a boiling chip. Isoamyl nitrite (0.35 mL, 2.9 mmol) was added slowly via syringe to the soln, and the soln was allowed to gently reflux over a sand bath for 5 min. Another soln was made in a separate reaction tube by dissolving anthranilic acid (0.250 g, 1.82 mmol) in glyme (2 mL). This anthranilic acid/glyme soln was added to the refluxing soln dropwise via pipette to form a red soln. After 5 min, the reaction tube was gently shaken and a color change from red to dark brown was observed. After cooling, ethanol (10 mL) and sodium bicarbonate (5 mL) were added, forming a precipitate. The resulting solid was collected using vacuum filtration. The light yellow precipitate was washed twice with cold water (5 mL) and twice with cold ethanol (5 mL), then filtered to dryness. The resulting solid was then recrystallized using a nitrobenzene/ethanol solvent pair (1 mL). Vacuum filtration was used to yield a white mass of precipitate. The final product, tetraphenylnapthalene was massed (0.357 g, 0.825 mmol, 62.5%): mp 198.0-203.0