A Strained Cyclononadienyne

The title compound, methyl 8-chlorobicyclo[7.1.0]deca-1,8-dien-4-yn-2-carboxylate C₁₂H₁₁ClO₂, crystallizes with two chemically equivalent and essentially geometrically and conformationally identical molecules in the asymmetric unit. A cyclopropane ring is fused to a nine-membered ring such that it is flanked by two double bonds and the presence of a triple bond in the larger ring generates considerable strain, evidenced in the marked non-linearity of the alkyne unit [165.2 (2)-168.4 (2)° at the carbon atoms] and the wide angles within the nine-membered ring at the ring fusion atoms [153.09 (10)-155.5 (2)°].

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