Syntheses and Structures of Functionalized Macrocyclic Carbon Nanohoops Bearing a [9]Cycloparaphenylene or a Higher Homological Unit

The Diels-Alder reactions between (<i>E</i>,<i>E</i>)-1,4-bis(4-bromophenyl)-1,3-butadiene and dienophiles and the use of the resulting adducts for macrocyclization and aromatization were established. Several functionalized macrocyclic structures bearing a functionalized [9]cycloparaphenylene or a higher homological unit were isolated. The distribution of the macrocyclic structures was found to be governed by the structures of the starting Diels-Alder adducts. An empirical correlation between the angles of the two 4-bromophenyl groups of the X-ray structures of the Diels-Alder adducts and the macrocyclization steps was observed.