2.4- Dioxo-4-arylbutanoic acids

Hydroxy-9-arylphenalenones are also conveniently prepared by condensation of 2,7-dihydroxynaphthalene and its derivatives with 2,4-dioxo-4-arylbutanoic acids as shown in Scheme IX 71). 

Intramolecular cyclisation of a 4-arylbutanoic acid system is also an important step in a convenient synthesis of the polycyclic system, chrysene, which is formulated and described in Expt 6.12. Here, methyl cinnamate is first subjected to reductive dimerisation to give methyl meso-ft,y-diphenyladipate, which is accompanied by some of the ( + )-form. The meso isomer (16) is the most easily isolable and cyclisation occurs smoothly in sulphuric acid to yield the diketone 2,1 l-dioxo-l,2,9,10,ll,18-hexahydrochrysene, which is obtained as the trans form (17) as shown in the following formulation. Clemmensen reduction of this ketone followed by dehydrogenation (in this case using selenium) completes the synthesis of chrysene. 

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See also in sourсe #XX -- [ ]

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