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A synthesis of o-ethynylcinnamaldehyde(IV) starting from o-ethynylbenzaldehyde(I) by the Wittig reaction is described.

In order to examine the paratropic nature expected for a thirteen-membered ring system arising from polarization of the carbonyl group, the two benzannelated bisdehydro[13] annulenones, VI and IX, were prepared respectively by the aldol condensation of an appropriate aldehyde and an appropriate ketone followed by the oxidative coupling of the resulting acyclic ketone containing terminal acetylene groups. The NMR spectra indicate that both of VI and IX, as well as the respective protonated species, VII and X, are paratropic and paratropicities decrease in the sequence of VI>IX with the increasing number of fused benzene ring. The dibenzannelated annulenone (IX) and its precursor (VIII) were converted into the corresponding alcohols or ethers (XIIa, XIIb and XIa, XIb), respectively, to test the presence of the paratropic nature of IX. The NMR spectra of XIa, XIb and XIIa, XIIb, in addition to those of VIII and IX, suggested that IX seemed to be weakly paratropic. An attempt made to prepare the dibenzannelated bisdehydro[13]annulenyl anion (XIII) was unsuccessful.

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