Cyclic tolans

Figure 2. Alternation of melting points of o,p -bridged cyclic tolans (144) - . Reproduced by permission of the Chemical Society of Japan.

Table 5. Molecular geometry and electronic spectral data of cyclic diphcnyidiacetylenes and cyclic tolans...

The intramolecular approach of Staab and Graf, shown in Scheme 4, precluded formation of 5, but was considerably more involved [12]. The cyclic dienyne 6 was afforded by Wittig reaction of o-phthaldialdehyde with the corresponding bis(ylide) derived from tolane. Bromination of 6 and subsequent treat-... 

The high reactivity of this system is demonstrated by the fact that the cyclic ring system is cleaved by sodium hydroxide to give ( r-l,2-diphenylvinyl)phosphinic acid and is thermally unstable giving tolan at 120°C (fS9). The extension of this synthetic route to other phosphorus or other heteroatom derivatives has not yet been tested. 

Cyclic acetylide titanium complexes containing the 0-bis(ethynyl)tolane ligand have been synthesized, characterized, and used to prepare a heterobimetallic derivative with an Ni atom coordinated to three alkyne functionalities (Scheme 501).1286... 

Using a suspension of silver salts in alcohol or acetonitrile for isomerization of tolane-2-carboxylic acid leads to a change in the ratio between the resulting 3- and y-lactones to preferential formation of the five-membered cyclic ester... 

Cycloalkenylcarbenes are carbenes that contain a cyclic side group. Tolane is the major decomposition product from the decomposition of diphenylcyclopropene diazomethane and a minor product is formed via normal ring expansion (Scheme 22). Cycloheptatrienylcarbene yields only benzene, acetylene, and heptafulvene in addition to cyclooctatetraene (Scheme 23). 

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