Cycloaddition Reactions of Alkynyl‐[2.2]paracyclophanes Toward Fluorenone and Benzene Analogs

Cycloaddition reactions of ethynyl[2.2]paracyclophane and methyl 3‐([2.2]paracyclophan‐2‐yl)propynoate were studied under different conditions. The former one participated in catalytic cross‐cyclotrimerization with various 1,6‐heptadiynes, giving rise to the corresponding 2‐aryl‐[2.2]paracyclophane in moderate yields. Interestingly, attempts at its homocyclotrimerization yielded only 1,4‐di[2.2]paracyclophanylbut‐3‐en‐1‐ynes. The latter readily participated in a Diels–Alder reaction with tetramethylcyclobutadiene‐AlCl 3 adduct, furnishing Dewar benzenes, which were used as the key intermediate in the synthesis of racemic and chiral [2.2]paracyclophane‐fluorenone hybrid.