Completely spirocyclopropanated macrocyclic oligodiacetylenes: the family of \"exploding\" [n]rotanes.
A general approach to the family of completely spirocyclopropanated macrocyclic polydiacetylenes, i.e., cyclic dehydrooligomers of 1,1-diethynylcyclopropane, was reported. The characterized examples of these [n]rotanes are for n = 5, 6, 7, 8, 9, 10, and 12. X-ray crystal structure analyses for the hydrocarbons with n = 5, 6, 7, and 8 disclose a strong electronic interaction between the cyclopropane and the acetylene units leading to a significant shortening of the distal and lengthening of the proximal cyclopropane bonds. While the five-sided compd. can occur as a planar or envelope-shaped mol., depending on the solvent from which crystals are grown, the six-, seven-, and eight-sided mols. all have chair conformations. While the butadiyne units in the five-sided and six-sided compds. are bent slightly outwards, those in the seven- and eight-sided mols., resp., are bent distinctly inward. All these compds. are extremely high-energy mols.: when struck with a spatula or a pestle, they go off with a puff to yield black soot.
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