Mixed Oligoyne-Diyne Macrocycles

Structural Features and the Quest for Homoconjugation in Expanded [/ijPericyclines and Exploded [nJRotanes 

Similarly, the chair of the 30-membered ring of exp-[6]rotane 166 with an average torsional angle of =41.4(4)° is less puckered than cyclohexane ( =55.1°) [58] and [6]rotane ( =54.6°) [56]. 

The most remarkable structural features of the planar cyclic mixed trisethyne-monobutadiyne pentaacetylenes 181 and 62 are their drastically bowed diyne moieties [18]. The acetylenic carbon atoms deviate from linearity by an average of 11.7° in 181 and even 13.4° in 62. The internal C-C-C angle is smaller for 181 (103.8°) than for 62 (109.2°). The disparity of the C-C bond lengths in the spirocyclopropane moieties of 62 is analogous to those observed in the expanded [n]rotanes 165-168. 

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