Phenyl acetylene trimerization

Phosphenated polystyrene NiCIi PdClit-AgBF4 Cyclotri- and tetramerization of ethyl propiolate and cyclo-trimerization of phenyl-acetylene and various olefins British Petroleum Co. Ltd., 1972 Kaneda et aL, 1977... 

Trialkyl and triaryl Cr(III) compounds are effective in promoting the cyclic trimerization of disubstituted acetylenes to aromatic hydrocarbons 222, 457). In the reaction of Ph3Cr -3THF with 2-butyne, the bisarene complexes of hexamethylbenzene and 1,2,3,4-tetramethylnaphthalene are obtained, as well as the free aromatic hydrocarbons 222). It is clear that a phenyl substituent has been incorporated in the formation of the coordinated and uncoordinated 1,2,3,4-tetramethylnaphthalene. Al-... 

The phase-transfer-catalysed trimerization of various acetylenes PhC=CR (R = Me, Et, Ph or Ac) in the presence of rhodium(III) chloride and Aliquat 336 in 1,1,2,2-tetrachloroethane - water to yield mainly the benzene derivatives 575 has been reported. Biphenyldiazonium salts 576 (X = H, Cl or MeO) are converted into phenanthrenes 578 by the action of terminal acetylenes 577 (R = Ph, SiMes or C02Et) in pyridine. 2-Phenyl-1-naphthyldiazonium tetrafluoroborate (579) similarly affords the substituted chrysenes... 

The extent of the reaction is very much governed by the size of the alkynic substituents (Scheme 5) for example, if both substituents are bulky tert-butyl groups, no oligomerization occurs and only the 1 1 alkyne complex is formedJ When one tert-butyl is replaced by the smaller phenyl substituent, dimerization takes place and the cyclobutadiene complex is the only productJ However, diphenyl acetylene gives a mixture of the cyclobutadiene complex and the benzenoid trimerP The somewhat smaller carboxymethyl groups ensure that dimethyl acetylene dicarboxylate gives only the trimer.t ... 

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