Acetylene derivatives benzene ring trimerization

Dicarbonylbis(triphenylphosphine)nickel Benzene ring from acetylene derivs. by trimerization... 

Benzene ring from acetylene derivatives Trimerization... 

The trimerization reaction with benzene derivatives could sometimes follow a similar path but, since it also occurs with disubstituted acetylenes such as HOCH2C = CCH2OH, some other mechanism must also be operating. Schrauzer explained the cyclization of tolane with a catalyst based on bisacrylonitrilenickel and triphenylphosphine by the so-called V-complex, multicenter processes. With this process, three alkyne molecules would successively coordinate with nickel and then the ring closure would take place (See Figure 6). 

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