Acephenanthrylene benz indeno

The thermal disrotatory [n6] electrocyclization of cis-1,3,5-hexatriene systems has been extensively employed for the synthesis of cyclic hydrocarbons. The average enthalpy of activation is in the range of about 120 kJ mol 1 [36]. The incorporation of two of the hexatriene double bonds in phenyl rings (stil-bene, 1) stabilizes the precursor significantly and necessitates temperatures of 1050°C to obtain a 30% yield of phenanthrene (2, see Scheme 2, [37]). An enthalpy of activation of (250 20) kJ mok was estimated for the conversion of 9,9 -bifluorenylidene (3) to benz[e]indeno[l,2,3-hi]acephenanthrylene (4), a reaction that is accompanied by the radical initiated isomerization of 3 to diben-zo[g,p]chrysene (5, Scheme 2, [38]). It is assumed that both reactions 1 —> 2 and 3 —> 4 are initiated by an electrocyclic ring closure forming a 4 a,4 fr-dihydro-phenanthrene (la) intermediate. 

Results from many studies have been reported on the types and levels of PAHs, with particular emphasis on B[a]P, B[a]A, chrysene, benz[e]acephenanthrylene (benzo[fc]fluoranthene), benzoMfluoranthene, indeno[l,2,3-C(i]pyrene, DB[fl,/t]A, and benzo[g/t/]perylene. As noted by Menzie et al. (2533), all of these PAHs have been identified in exhausts or effluents from fossil fuel combustion sources, in soils, sediments, and water, and in a variety of commonly used foodstuffs. 

Brominated boronic acid 179 also served as a reagent for cross-coupling/direct arylation cascade annulation. The palladium-catalyzed reaction of 179 with 1,4-dibromonaphthalene (180) provided doubly annulated product 181 in 51% yield along with monoannulated and debrominated product 175 in 35% yield (Scheme 22.42) [65b]. Use of 1,8-dibromophenanthrene (182) as the coupling partner resulted in the production of a 1 1 mixture of benz[c]indeno[l,2,3-/tijacephenanthrylene (183) and benz[e]acephenanthrylene (184). 

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