Acetylene derivs benzene ring from

Synthesis with cobalt complex compounds Benzene ring from acetylene derivatives... 

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

Ortho photocycloaddition was first reported in a U.S. patent [1] dated September 3, 1957. Irradiation of benzonitrile in the presence of various alkenes resulted in the formation of derivatives of l-cyanobicyclo[4.2.0]octa-2,4-diene. The first ortho photocycloaddition to benzene was reported in 1959 by Angus and Bryce-Smith [2], who discovered that benzene and maleic anhydride react to form a stable adduct at 60°C under the influence of ultraviolet radiation. This 1 2 adduct was formed from one molecule of benzene and two molecules of maleic anhydride. Two years later, Bryce-Smith and Lodge [3] found that acetylenes could also be photoadded to benzene. The isolated products were cyclooctatetraenes, formed by ring opening of the primarily formed bicyclo[4.2.0]octa-2,4,7-trienes. Since those early years, hundreds of examples of ortho photocycloadditions of alkenes to the benzene ring and many mechanistic investigations have been reported and they will be discussed in this chapter. 

It is best to speak at this time of hydrocarbons derived from benzene by the substitution in the ring of unsaiurated open chain radicals. Just as the homologues of benzene are prepared by substitution of a saturated paraffin radical, methyl, ethyl, propyl, etc., in the benzene ring, so other series of hydrocarbons have been obtained by substituting radicals of the unsaturated open chain hydrocarbons of the ethylene and acetylene series. These new compounds will be poorer in hydrogen than the benzene series by two and four atoms respectively. 

Hitherto unknown 4,5-dihydrobenz[g]indole is obtained from 1-tetralone oxime and acetylene in the system KOH/DMSO in one stage (Scheme 1.30) [199]. 4,5-Dihydrobenz[g]indoles and their N-vinyl derivatives substituted at the benzene ring are isolated from the reaction of the corresponding 1-tetralone oximes and acetylene in the systems MOH/DMSO (Scheme 1.30) [200]. 

Crude Oil. Crude petroleum consists essentially of mixtures of paraffinic, naphthenic, and aromatic hydrocarbons containing from 1 to over 70 carbon atoms per molecule and may contain dissolved gases or solids. The naphthenic hydrocarbons are based on cyclopentane or cyclohexane or on fused C5 and Ce rings. There is no evidence of the existence of C3, C4, C7, or C7+ cycloparaffins in crude oil. Olefins, diolefins, and acetylenes are absent. The aromatics are mainly benzene derivatives naphthalene, tetralin, and their substituted derivatives have been isolated in a few cases. 

The action of zinc on the same cyclobutene derivative was also studied [6]. When the reaction was carried out in the presence of either dimethylacetylene or dimethyl acetylenedicarboxylate, hexa-methylbenzene and dimethyl tetramethylohthalate were isolated from the respective reaction mixtures. These products could arise by trapping of the cyclobutadiene by the acetylenes, and ring-opening of the adducts to give benzene derivatives. 

Carbene chemistry constitutes a particular but challenging field in organic synthesis. Carbenes offer a straightforward access to small rings (cyclopropanes, cyclopropenes) as well as to cycloheptatriene derivatives (the Buchner reaction) from cheap raw material (olefins, acetylenes, benzenic compounds, etc.). 

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