SYNTHESIS OF DIACETYLENE MACROCYCLES DERIVED FROM 1,2-DIETHYNYLBENZENE DERIVATIVES - STRUCTURE AND REACTIVITY OF THE STRAINED CYCLIC DIMER

Diacetylene macrocycles 2-4 (n = 1-3) (R = H, C4H9, C6H13, C10H21, C12H25, OC10H21) have been prepared from the oxidative coupling of 1,2-diethynylbenzene derivatives. These compounds can be produced in useful quantities and are of interest as precursors to novel conjugated organic polymers. The reported results indicate that when the R groups are large the dimeric macrocycle (n = 1) can be prepared in as high as 74% yield from the corresponding 1,2-diethynylbenzene in a one-step procedure. An alternate multistep procedure was found to produce the tetrameric macrocycle (n = 3, R = C6H13) in 45 % yield. The highly strained dimeric macrocycle was characterized by an X-ray structure and was found to be very reactive. The dimers undergo a rapid very exothermic polymerization at 100-125-degrees-C, indicative of a chain reaction. Reaction of the dimeric macrocycles with iodine results in intramolecular cyclization and a new 20pi electron tetraiodide fused ring system. Reaction of the tetraiodide with oxygen produces a related compound in which two of the iodides have been converted to ketones.