Phenanthrene oxidative rearrangement

Scheme IS depicts a high yield, general method for specific ortho alkylation of polycyclic aromatic hydrocarbons. In this example, biphenyl is subjected to reductive methylation followed by oxidative rearrangement with trityl tetrafluoroborate to give 2-methylbiphenyl. In unsymmetrical substrates the regioselectivity is poor phenanthrene gives a 3 2 mixture of 4-methyl- and 1-methyl-phenanthrene.

When deuterated phenanthrene oxide undergoes an epoxide rearrangement in water, 81% of the deuterium is retained in the product. 

The K-region phenanthrene oxide (68) undergoes photochemical ring-enlargement to (69) via the singlet excited state. A similar photochemical rearrangement for the K-region 3,4-epoxy-3,4-dihydropyrene was also reported. 

The l,3,5-triene-l,3-cyclohexadiene interconversion is a six-electron electrocycli-zation that requires a cis central double bond to occur.245 An important application of this rearrangement is the photocyclization of cis-stilbene to dihydrophenanthrene [Eq. (4.45)], which is usually further oxidized to phenanthrene 249... 

There are a large number of photochemical cydizations of aromatic compounds that lead initially to polycyclic, non-aromatic products, although subsequent rearrangement, elimination or oxidation occurs in many instances to form aromatic secondary products. The archetype for one major class of photocydization is the conversion of stilbene to phenanthrene by way of a dihydrophenanthrene (3.60). 

Oxadithiocines 29 are unstable, acid-sensitive compounds, obtained by photolysis of 4,8,10-trithiadibenzo-[cd,ij]-3ira ene 8-oxides 28 (see Section 14.08.8.2.5). Their additional photolysis results in the corresponding aldehydes or ketones and 4,8,9-trithiacyclopenta[rf7/]phenanthrene 30 as a major rearrangement product (Scheme 3 <1996CL655>). 

Enantiopure epoxides (3/ ,4Y)-dibenz[ 7, ]anthracene 3,4-oxide and (3iJ,4Y)-phenanthrene 3,4-oxide were synthesized via involved routes and were observed to spontaneously racemize. This racemization of arene oxides is in accordance with perturbation molecular orbital predictions based on resonance energy considerations, and presumably occurs via an electrocyclic rearrangement to the corresponding (undetected) oxepine tautomer (Scheme 17) <2001J(P1)1091>. 

Treatment of ketone 409 with lithium diisopropylamide (LDA) results in the ethyl 1,2-dihydroxybenzoate 410 in a 74% yield (equation 191) . The acid-catalyzed isomerization of diarene oxides derived from benz[a]anthracene, chrysene and benzo[c]phenanthrene gives mixtures of isomeric polycyclic phenols. Finally, it should be mentioned that dibenzo[i>, ]oxepin 411 undergoes an interesting rearrangement to 2-hydroxyphenylindene 412 (equation 192). 

Laarhoven has examined the fate of the dihydrophenanthrene intermediate (148) formed by photocyclisation of the styryl benzo-phenanthrenes (149). When the reaction is performed in the presence of iodine as oxidant the expected arene (150) is obtained but in the absence of the oxidant compound (148) rearranges to the more stable, isolable dlhydroarenes (151) and (152). This rearrangement is base catalysed and the proportions of (151) and (152) isolated depend upon the nature of the base and the solvent. 

The spiroisoxazoline 18, obtained from the nitrone 17 and dicyanoacetylene, rearranges to the pyiTolidinone 19 below 0 °C <97LA1691>. Irradiation of solvent-free mixtures of polycyclic aromatic hydrocarbons (anthracene, phenanthrene and pyrene) and the nitrile oxides mesitonitrile oxide or 3,5-dichloro-2,4,6-trimethylbenzonitrile oxide in a microwave oven at 650 W for 3.5-10 min. yields isoxazolines, e.t . 20, from phenanthrene <97H(45)1567>. 

Certain polycyclic aromatic hydrocarbons can be converted to their epoxides, as typified by the reaction of phenanthrene with DDO (eq 9). Aromatic heterocycles like furans and benzofurans also give epoxides, although these products are quite susceptible to rearrangement, even at subambient temperatures (eq 10). The oxidation of heavily substituted phenols by DDO leads to quinones, as shown in eq 11, which illustrates the formation of an orthoquinone. 7 The corresponding hydroquinones are intermediates in these reactions, but undergo ready oxidation to the quinones. 

Other polycyclic aromatic hydrocarbons such as phenanthrene, anthracene, and fluoranthene are converted to the corresponding quinones on oxidation with CAS. Whereas 1-methylnaphthalene gives 1-naphthaldehyde under the conditions, 1-phenyl- and 1-bromonaphthalene react to form some 2-substituted naphthoquinones through an interesting rearrangement (eq 2). ... 

Pyrene and 4-methyl- and 4,5-dimethyl-pyrene have been prepared from 4//-cyclopenta[de/]phenanthrenes by a reaction sequence involving carbox-ylation and then conversion, through the ester, into the carbinol, which undergoes Wagner-Meerwein rearrangement. 5,12-Diphenylnaphthacene undergoes photochemical oxidation,giving a mixture of endoperoxides (397) and (398) the major product, (397), was subsequently converted into the diol (399). 

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