Barrelene benzobarrelene

Di-ir-Methane Rearrangement of Barrelene, Benzobarrelene, Dibenzobarrelene, and Related Derivatives... 

Barrelene, benzobarrelene and dibenzobarrelene derivatives are readily synthesized by Diels-Alder reactions of arenes with alkenes. For barrelene and related derivatives, the DPM rearrangement proceeds solely from the triplet state, giving semibullva-lenes (Scheme 4.1) [3, 4]. 

Other heterodienophiles include diethyl azodicarboxylate, tosyl cyanide and phosphaalkynes. Barrelene, benzobarrelene and 2,3-naphthobarrelene react at 100-110 °C (sealed tube) with diethyl azodicarboxylate to give as the main product the corresponding homo-Diels-Alder adduct 27. ... 

The spectral properties of benzobarrelene are as follows infrared (potassium iodide) cm. strong peaks 1460, 1325, 790, 750, 690, 660 proton magnetic resonance (chloroform-d) S (multiplicity, number of protons, assignment) 4.9 (multiple , 2, bridgehead H), 6.8-7.3 (multiple , 8, aryl and vinyl H). The reported melting point is 65.5-66°.From 20 g. of tetrachlorobenzo-barrelene the submitters obtained 8.3-8.8 g. (79-83%) of benzobarrelene, m.p. 64-65°. 

Benzobarrelene is similar to barrelene in that rearrangement to benzo-cyclooctatetraene takes place from the singlet state while benzosemibullvalene is formed from the triplet state<44> ... 

Bridges other than methylene, e.g. those present in benzobarrelene and its dihydro derivative, also provide for reactive di-ir-methane systems. " In the benzobarrelene case, aryl-vinyl or vinyl-vinyl bonding is possible. As shown in equation (15), the products derived from these two pathways are distinctive for the labelled substrate. This aspect has been studied for several barrelenes containing different aromatic groups, including naphthalene (both at the 1,2- and 2,3-positions), anthracene, etc. The observed products are rationalized most frequently via vinyl-vinyl bridging. Similar behavior is exhibited by diben-zobarrelene and related systems. ... 

In contrast to the tetrafluorobenzonorbomadiene series, tetrafluorobenzo-barrelene (171) is attacked only from the ewfo-side by Br+ and I+, although C1+ is less selective halogenation is invariably accompanied by rearrangement of the hydrocarbon skeleton. However, the benzobarrelene reacts with perbenzoic acid to yield the ew-epoxide (172) and the endo,exo-diepoiadmono-epoxide with boron trifiuoride etherate yields... 

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