SKIPPED CYCLIC ENEDIYNES AND DIENEDIYNES .1. SYNTHESIS, SPECTROSCOPIC PROPERTIES, AND REACTIONS OF A NEW HYDROCARBON RING FAMILY

The three skipped cyclic C12H12 dienediynes, 4,9-dimethylene-1,6-cyclodecadiyne (1), (Z,Z)-4,10-cyclododocadiene-1,7-diyne (2), and 10-methylene-(Z)-4-cycloundecene-1,7-diyne (3), have been synthesized by cyclization of dilithium salts of diterminal enediynes with the corresponding dihalogenides. This simple approach only worked (with approx. 5% yield) when no CuCl catalyst was used. Besides 1-3, 4,9-diisopropylidene-1,6-cyclodecadiyne (30), the cyclic enediynes (Z)-4-cycloundecene-1,7-diyne (19) and (Z)-4-cyclododecene-1,7-diyne (20), as well as 4-methylene-1,6-cyclodecadiyne (22), 4-methylene-1,6-cycloundecadiyne (23), and their isopropylidene congeners 25 and 28 have been synthesized. Partial hydrogenation of 1-3 gives the corresponding homoconjugated tetraenes 37-39. The reaction of 30 with dicarbonyl(eta5-cyclopentadienyl)cobalt yields a superphane of two cyclobutadiene units, stabilized by two CpCo moieties (47). The two cyclobutadiene rings are connected by four 2-isopropylidenepropano bridges. An X-ray investigation of the superphane shows that all four bridges adopt a pinwheel-like conformation.