Completely Spirocyclopropanated Macrocyclic Oligodiacetylenes: The Family of “Exploding” [n]Rotanes

A general approach to the family of completely spirocyclopropanated macrocyclic polydiacetylenes, that is, cyclic dehydrooligomers of 1,1‐diethynylcyclopropane 4, is reported. The characterized examples of these “exploding” [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 compound 18 can occur as a planar or envelope‐shaped molecule, depending on the solvent from which crystals are grown, the six‐ (19), seven‐ (20), and eight‐sided (21) molecules all have chair conformations. While the butadiyne units in 18 and 19 are bent slightly outwards, those in the seven‐ and eight‐sided molecules 20 and 21, respectively, are bent distinctly inward. All these compounds are extremely high‐energy molecules: when struck with a spatula or a pestle, they go off with a puff to yield black soot.