Synthesis of Diacetylene Macrocycles Derived from 1,2-Diethynylbenzene Derivatives: Structure and Reactivity of the Strained Cyclic Dimer

Article abstract of DOI:10.1021/jo00085a016

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 74percent 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 45percent 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 deg C, indicative of a chain reaction.Reaction of the dimeric macrocycles with iodine results in intramolecular cyclization and a new 20? 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.