Benzyne, trimerization reactions

Generation of benzyne (see also 1, 560). Campbell and Rees1 point out that the generation of benzyne from this precursor by oxidation with lead tetraacetate differs from other methods in that, in the absence of a trapping agent, the dimer, diphenylene, is formed in yields as high as 83%. The trimer, triphenylene, is formed in less than 0.5% yield. Addition reactions of benzyne generated in this way with 1,3-dienes have been discussed.2... 

Cycloadditions. Several versions of this reaction have been developed, leading to hexabenzotriphenylene (trimerization of benzyne> and heavily substituted dihydroisobenzofurans. 

The first metal-catalyzed reaction of arynes was described by Guitian in the late 1990s consisting in the cyclotrimerization of benzyne to yield triphenylene 100 (Scheme 12.51) [89]. These and other authors have extended this process to the trimerization of a variety of arynes, leading to polycyclic aromatic hydrocarbons (PAHs). 

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