1.2- Dibenzoyl benzene

Although the sulfone activated biphenyl and the ketone activated naphthalene moiety for the displacement polymerization have been reported by Attwood et al. [11], these were rediscovered by Cummings et al. [12] and Hergenrother et al. [13], respectively, for the synthesis of poly(aryl ethers). Recently, Singh and Hay [14] reported polymers containing 0-dibenzoyl benzene (1,2,3) moiety by reaction between bis(O-fluorobenzoyl) benzene or substituted benzene with bisphenates of alkali metal salt in DMAC as follows ... 

The synthetic route represents a classical ladder polymer synthesis a suitably substituted, open-chain precursor polymer is cyclized to a band structure in a polymer-analogous fashion. The first step here, formation of the polymeric, open-chain precursor structure, is AA-type coupling of a 2,5-dibromo-1,4-dibenzoyl-benzene derivative, by a Yamamoto-type aryl-aryl coupling. The reagent employed for dehalogenation, the nickel(0)/l,5-cyclooctadiene complex (Ni(COD)2), was used in stoichiometric amounts with co-reagents (2,2 -bipyridine and 1,5-cyclooctadiene), in dimethylacetamide or dimethylformamide as solvent. 

A slow, dark reaction of 138 with oxygen was also reported by other workers,but it was recently claimed that 138 in solution does not absorb oxygen in the dark, autoxidation only took place in the presence of azobisisobutyronitrile. A peroxide with mp 127.5-128.5°C and a molecular weight of 1350 + 50 was obtained (241 = 4-5) 35% o-dibenzoyl-benzene could also be isolated. The peroxides decomposed in benzene (half-life 72 h at 5O C) to give 140. 

The 1,4-biradical formed in the interaction of norbornene with 0-dibenzoyl-benzene was trapped in an intramolecular fashion by the... 

Dichlorobenzophenone Phenyl benzoate 4 -Methoxybenzophenone Acetophenone 0-Dibenzoyl benzene... 

Diphenylisoindole can be conveniently prepared from o-dibenzoyl benzene, for example, by treatment with ammonium formate (Leuckart reaction).5,33 The same type of reaction is observed when the aryl diketone... 

Scheme 2 Synthesis of ladder-type polyphenylenes using para- and meto-dibenzoyl benzene building blocks, and dehydrogenation of 3b to polymer 3 with para-quinodimethane repeat units. No control over the configuration at the bridging methylene carbons could be achieved...

Hay has reported the synthesis of poly(aryl ether ketones) containing o-dibenzoylbenzene moieties by the polymerization of 1,2-bis(4-fluorobenzoyl) benzene with various bisphenolates in DM AC (32). Transformation of the o-dibenzoyl(benzene) moiety in the polymer chain to a heterocycle by cyclization with small molecules was developed as a means of increasing the pol5mer chain stiffness and solvent resistance. It was demonstrated that reaction of the polymer with hydrazine monohydrate in the presence of a mild acid in chlorobenzene converted the poly(aryl ether ketone) to a poly(aryl ether phthalazine), a new class of heterocyclic-containing polyether (Scheme V) (33). Likewise, reaction of the polymer with benzylamine in a basic medium led to amorphous, thermally stable poly(aryl ether isoquinolines) (Scheme V) (34). Another example of the use of the o-benzoyl cyclization strategy is the intramolecular ring closure of poly(aryl ketones) containing 2,2 -dibenzoylbiphenyl units to form poly(aryl ether phenanthrenes) (35-37). 

The photocycloaddition of triplet benzophenone to norbornene was originally reported by Scharf and Korte. The photoproduct 101 that is formed in high exo-selectivity could be thermally cleaved to the 5,e-unsaturated ketone 102, an appHcation of the carbonyl-olefin metathesis (COM) concept. The 1,4-biradical formed in the interaction of norbornene with o-dibenzoyl-benzene was trapped in an intramolecular fashion by the second carbonyl moiety. A highly regioselective reaction of triplet benzophenone was reported with 5-methylenenorborn-2-ene, with preferential attack toward the exo CC double bond. A number of publications have discussed the photocycloaddition reactions of triplet carbonyl compounds to norbornadiene and quadricyclane, as weU as the competition between the Paterno-Biichi reaction and the sensitized norbornadiene/quadricyclane interconversion. Oxetane formation has also been reported for the photoreaction of biacetyl and para-quinones with benzvalene. ... 

Benzene, o-dibenzoyl-isoindole synthesis from, 4, 330 Benzene, diethynyl-polymerization, 1, 295 polymers... 

Fig. 12.3. NMR spectra recorded during thermal decomposition of dibenzoyl peroxide. Singlet at high field is due to benzene other signals are due to dibenzoyl peroxide. [From H. Fischer and J. Bargon, Acc. Chem. Res. 2 110 (1969). Reproduced by permission of the American Chemical Society.]...

Lobelanidine, C22ll2g02N. Crystallises from alcohol in laminae, m.p. 150°, [ ] D i 0°, distils unchanged in a vacuum and is readily soluble in acetone or benzene, sparingly so in ether. The hydrochloride, m.p. 135-8°, forms needles from alcohol the hydrobromide has m.p. 188-190°. The dibenzoyl derivative melts at 109-10° and the hydrochloride of the diacetyl derivative at 214-5°. The methiodide becomes tiu-bid at 178-5° and clears at 200°. Phosphorus trichloride converts the base into dichlorolobelane... 

It is understandable that dihydro adducts should be formed by polycyclic compounds and not by benzene or pyridine, because the loss of aromatic resonance energy is smaller in the former than in the latter process, (c) When dibenzoyl peroxide is decomposed in very dilute solution (0.01 Af) in benzene, 1,4-dihydro biphenyl is produced as well as biphenyl, consistent with addition of the phenyl... 

This last result bears also on the mode of conversion of the adduct to the final substitution product. As written in Eq. (10), a hydrogen atom is eliminated from the adduct, but it is more likely that it is abstracted from the adduct by a second radical. In dilute solutions of the radical-producing species, this second radical may be the adduct itself, as in Eq. (12) but when more concentrated solutions of dibenzoyl peroxide are employed, the hydrogen atom is removed by a benzoyloxy radical, for in the arylation of deuterated aromatic compounds the deuterium lost from the aromatic nucleus appears as deuterated benzoic acid, Eq. (13).The over-all reaction for the phenylation of benzene by dibenzoyl peroxide may therefore be written as in Eq, (14). 

For the synthesis of the target structures, it is absolutely necessary to introduce solubilizing substituents in the positions peripheral to the benzoyl substituents. The primary coupling product, 117, a poly(2,5-dibenzoyl-l,4-phenyl-ene) derivative - a poly(para-phenylene) with two benzoyl substituents in each structural unit - is, as expected, very poorly soluble. Highly substituted monomers (2,5-dibromo-l,4-bis(3,4-dihexyloxy-benzoyl)benzene), containing four solubilizing alkoxy groups per monomer unit, allow the synthesis of polymeric materials with M of about 12,000 and M, of about 22,000 [139]. 

G. Lundeen and R. Livingston 62> observed weak chemiluminescence when dibenzoyl peroxide decomposed in chlorobenzene or />-dichloro-benzene. 

The 1,4-diketone 1,2-dibenzoylethane 151 can be transformed in one step into 3,4-dibenzoyl-l,2,5-thiadiazole 152 when treated either with preformed trithiazyl trichloride in tetrachloromethane (Equation 29) <1997J(P1)2831> or with urethane, thionyl chloride, and pyridine in benzene (Katz reagent) <2002ARK90> (see also Section 5.09.9.2.l(iii)(b)). Similarly, treatment of 1,3-diketones 153 with tetrasulfur tetranitride antimony pentachloride complex in toluene at 100 °C < 1998J(P 1 )2175 >, or trithiazyl trichloride in boiling tetrachloromethane < 1997J(P 1)2831 >, affords 4-substituted-3-aroyl-l,2,5-thiadiazoles 154 (Equation 30). 

When either diacetyl of dibenzoyl peroxide is decomposed in benzene in the presence of metallic mercury an organomercuric salt is obtained.117 The reaction is similar to the mirror removing reaction observed in gas phase experiments. 

The generation of the benzoyloxyl radical relies on the thermal or photoinitiated decomposition [reaction (49)] of dibenzoyl peroxide (DBPO). An early study (Janzen et al., 1972) showed that the kinetics of the thermal reaction between DBPO and PBN in benzene to give PhCOO-PBN" could be followed by monitoring [PhCOO-PBN ] from 38°C and upwards. The reaction was first order in [DBPO] and zero order in [PBN], and the rate constants evaluated for the homolysis of the 0—0 bond in DBPO (k = 3.7 x 10-8 s-1 at 38°C) agreed well with those of other studies at higher temperatures. Thus in benzene the homolytic decomposition mechanism of DBPO seems to prevail. 

Dibenzoyl peroxide adds to 42 in benzene, again via 49, forming 51. The reaction also works with other imidazoles having at least one aryl and up to two alkyl substituents. ... 

Diaroylcyclohexadienes which can be prepared from acyclic dienes and dibenzoyl-acetylene undergo ring closure with p-toluenesulfonic acid in benzene to afford benzo[c Jfurans. 

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