2- Hydroxybenzophenone, reaction with

The five-coordinate complexes Ir(CO)(PPh3)2L, where HL = /3-diketone, A-benzoyl-A-phenyl-hydroxylamine, salicylaldehyde, 8-hydroxyquinoline, 2-hydroxybenzophenone, 2-hydroxy-8-methoxybenzophenone, were prepared from [Ir(CO)(PPh3)2Cl].632 The resulting compounds all underwent oxidative addition reactions with Br2. Reaction of [(cod)2IrCl]2 with N-substituted 3-hydroxy-2-methyl-4-pyridine gives the bichelated complex (389). 33... 

The solute benzene radical cation was formed on pulse radiolysis of an acidic aqueous solution of benzene. The transient optical absorption bands (A-max = 310, 350-500 nm) were assigned to the solute benzene radical cation which is formed on acid-catalysed dehydration of the OH adduct. The radical cation is able to undergo an electron-transfer reaction with Br and was found to be a strong electron oxidant. Pulse radiolysis has been used to study the complex reaction that follows electron addition to hydroxybenzophenones (HOBPs). The various radical species involved have been characterized spectrally and their p/fa values evaluated. The differences... 

The enhanced reaction in ethanol is attributed to weakening of the tight, intramolecular hydrogen bond which is believed to facilitate photoenolization of 2-hydroxybenzophenone. t>-Hydroxybutyrophenone undergoes photoenolization in preference to Type II cleavage.25 The enol of o-benzylbenzo-phenone (2) forms a Diels-Alder adduct with dimethyl acetylenedicarboxylate, indicating that reaction with a reactive substrate is possible.30... 

Another example of commercial interest is the Fries rearrangement of the benzoate ester of resorcinol to afford 2,4-dihydroxybenzophenone, the precursor of the UV-absorbent 4-0-octyl-2-hydroxybenzophenone. Reaction of benzoic acid with one equivalent of resorcinol (see Fig. 2.22), over various solid catalysts, in chlorobenzene as solvent, with continuous removal of water, was investigated by Hoefnagel and van Bekkum [68]. H-Beta was slightly less active than the ion-ex-... 

The substituted 2-hydroxybenzophenone, 2-(2-hydroxy-4-di-n-butylamino)-benzoylbenzoic acid underwent reaction with 4-methoxy-2-methyldiphenyl-amine in concentrated sulphuric acid at 10-1 during 20 hours followed by work-up in alkaline solution and a final treatment by refluxing in hot toluene for 2 hours to give 2-anilino-3-methyl-6-dibutylaminofluoran in 88% yield (ref.81). 

Reaction of resorcinol with benzotrichloride or benzoyl chloride yields 2,4-di-hydroxybenzophenone, which, with octyl chloride, forms 2-hydroxy-4-octyloxy-benzophenone, one of the most important UV absorbers for the stabilization of polyolefin films. 

Preparation from thioxanthen-9-one 10,10-dioxide (SM) by a three-steps synthesis refluxing SM in 2% sodium hydroxide-65% dioxane-water solution for 4 h gave the 2-(2-hydroxybenzoyl)-phenylsulfinic acid (25%). The former, by reaction with mercuric chloride in refluxing aqueous acetic acid for 4 h, led to the 2-chloromercuri-2 -hydroxybenzophenone (69%). Removal of the chloromercury group was achieved with concentrated hydrochloric acid in refluxing ethanol for 2 h (91%) [62],... 

Sodium methoxide (1.2 g) in dimethylformamide (150 ml) was stirred with 3,5-dim ethoxy-4 reaction mixture was then treated with /3-morpholinoethyl chloride (3.4 g) and heated for 1 hour at 140°C, then evaporated to dryness, and treated with water to give a solid material. The mixture was filtered, washed and crystallized from cyclohexane to give 3,5-di-methoxv-4 -chloro-4-( morpholinoethoxy)-benzophenone (6.5 g), MP 91°C to 92°C. The product was then reacted at about 0°C with gaseous hydrogen chloride in ether to give, after crystallization from isopropanol, the corresponding hydrochloride which hada MPof 187.9°C. 

The reaction of phenol benzoylation catalyzed by a H-P zeolite (Si/Al ratio 75) has been studied, with the aim of determining the reaction scheme. The only primary product was phenylbenzoate, which then reacted consecutively to yield o- and p-hydroxybenzophenone and benzoylphenylbenzoate isomers, via both intermolecular and intramolecular mechanisms. 

Figure 2 plots the effect of phenol conversion on the distribution of products. The following compounds were obtained (i) phenylbenzoate, (ii) 0- and p-hydroxybenzophenone, and (iii) 0- and p-benzoylphenylbenzoate. The first product was obtained with 100% selectivity only at moderate conversion, for low reaction times. In fact, when the conversion of phenol increased due to longer reaction times. 

The data clearly indicate that the only primary product was phenylbenzoate, while all the other compounds formed by consecutive reactions upon the ester. Therefore, the scheme of reaction is that one summarized in Figure 3. The formation of the ester as the only primary product represents one important difference with respect to the Friedel-Crafts benzoylation of phenol with benzoylchloride or benzyltrichloride, catalyzed by AICI3. In the latter case, in fact, the product of para-C-acylation (p-hydroxybenzophenone) is the main product of reaction this is due to the fact that AICI3 coordinates with the 0 atom of the hydroxy group in phenol, and makes it less available for the ester formation, due to both electronic and steric reasons. 

The consecutive formation of o-hydroxybenzophenone (Figure 3) occurred by Fries transposition over phenylbenzoate. In the Fries reaction catalyzed by Lewis-type systems, aimed at the synthesis of hydroxyarylketones starting from aryl esters, the mechanism can be either (i) intermolecular, in which the benzoyl cation acylates phenylbenzoate with formation of benzoylphenylbenzoate, while the Ph-O-AfCL complex generates phenol (in this case, hydroxybenzophenone is a consecutive product of phenylbenzoate transformation), or (ii) intramolecular, in which phenylbenzoate directly transforms into hydroxybenzophenone, or (iii) again intermolecular, in which however the benzoyl cation acylates the Ph-O-AfCL complex, with formation of another complex which then decomposes to yield hydroxybenzophenone (mechanism of monomolecular deacylation-acylation). Mechanisms (i) and (iii) lead preferentially to the formation of p-hydroxybenzophenone (especially at low temperature), while mechanism (ii) to the ortho isomer. In the case of the Bronsted-type catalysis with zeolites, shape-selectivity effects may favor the formation of the para isomer with respect to the ortho one (11,12). 

In our case, all the compounds obtained by transformation of the intermediate, phenylbenzoate, were primary products. This indicates that the following parallel reactions occurred on phenylbenzoate (1) the intramolecular Fries transposition generated o-hydroxybenzophenone, (ii) phenylbenzoate acted as a benzoylating agent on phenol, to yield p-hydroxybenzophenone (with also possible formation of the ortho isomer) and phenol and (iii) phenylbenzoate acylated a second molecule of phenylbenzoate to generate benzoylphenylbenzoates, with the co-production of phenol. 

A reaction vessel was charged with 4-hydroxybenzophenone (940 mmol) dissolved in 700 ml of 2-butanone and then treated with K2CO3 (1.41 mol) and heated to 65°C. This mixture was next treated with the dropwise addition of allyl bromide (1.41 mol) and stirred for 6.5 hours at 65°C. The slurry was filtered, and the filtrate was extracted with 500 ml of 1% hydrochloric acid. The organic layer was isolated, dried over MgS04, and concentrated. The product was isolated in 92% yield a pale yellow solid. 

Arenes of the type ArX-Y, where X may be O, S, or NR, frequently undergo facile photoinduced homolytic cleavage of the X-Y bond with the Y radical subsequently attacking the aromatic ring. The photo-Fries reaction is the most common process of this type and has been reported within the year for aromatic esters which form part of a ptolymer chain or are pendant groups on a polymer chain. In the former case, the rearrangement of fluorene-based polyacrylates [for example, (292)] was studied. Formation of the o-hydroxybenzophenone moiety in the product (293) was monitored by u.v. and... 

UV absorbers (UVA) act by absorbing UV light to retard the photolysis of hydroperoxides. Typical examples are based on 2-hydroxybenzophenones (AO 28) and 2-hydroxybenzotriazoles (e.g.. Table 1, AOs 29-32) both are photo-stable with high molar absorptions over the region 300-360 nm. Their activity is based essentially on absorption of the harmful UV-radiation and its harmless dissipation as heat. For example, in 2-hydroxybenzophenones, UV-light induces intramolecular hydrogen transfer to yield an enol, which reverts back to the original ketone in a radiationless process, Reaction 4. 

The reaction rate was shown to be related to the accessibility of the acid sites-H-MFI zeolite was practically inactive and Nafion was the most active catalyst. With all the catalysts, not only the desired p-hydroxybenzophenone (/ -HBP) product but also j3-benzoxybenzophenone (p-BXBP) and o-hydroxybenzophenone (o-HBP) were formed. The para products result from benzoylation of phenol (formed by hydrolysis of PB) or of PB and o-HBP from the intramolecular rearrangement of PB. The selectivity to p-HBP can, therefore, be significantly improved by adding phenol to the reactant mixture [4]. Unfortunately, thermodynamic limitations arising from the low polarity of the medium employed (even with very polar solvents such as sulfolane) seems to preclude the use of a solid acid for the production of diphenol monomers from diphenyl benzoate [4]. 

Unmodified BEA zeolite, on the other hand, shows the highest activity in the acylation of phenol wifh benzoic anhydride. Phenyl benzoate (PB) is the main product (61% yield), accompanied by C-acylated products (35%), with an interesting para-selectivity (ortho/para = 0.48). When the reaction time is increased from 4 to 20 h, an increase in para-hydroxy-benzophenone yield (from 11% to 23%) fogefher wifh a decrease in PB yield (from 79% to 64%) is observed however, a small increase in the orf/zo-hydroxybenzophenone yield (from 9% to 10%) cannof be avoided. The acfivify of the catalyst, together with its selectivity, does not distinctly decrease when the catalyst is used from fresh to firsf recycle. 

Arylation of salicylaldehydes. o-Hydroxybenzophenones are obtained when salicylaldehydes and diaryliodonium salts are brought together with PdCl2-LiCl. This same reaction had been realized before using Arl instead of the iodonium salts. 

The hydroxyl group has been replaced by a variety of substituents in some unusual reactions. 4-Hydroxybenzophenone and benzyltriethylammonium chloride in o-xylene upon treatment under anhydrous conditions with phosgene at 95-120°C during 5.5 hours gave 4-chloroformylbenzophenone in 99% yield (ref.46). 

Hydroxybenzophenone, introduced into a mixture of its 0-cyanide derivative in ether containing finely powdered potassium hydroxide with vigorous stirring and reaction at ambient temperature during 1 hour led to 2-(2-benzoylphenoxy>-... 

The effects that initiator derived residues and functional groups have on polymer properties is an area that needs further study. For example, as discussed above, benzoyl peroxide leads to the formation of benzoyloxyphenyl groups in PS. It is known that the polymerization of p-benzoyloxystyrene [155] and its copolymerization with styrene [156] leads to the formation of photo-reactive polymers. Upon irradiation these polymers undergo a facile photo-Fries Rearrangement resulting in the conversion of the benzoyloxyphenyl groups to hydroxybenzophenone moieties [157]. Other side reactions also lead to the formation of phenolic groups and free benzoyloxy radicals [155]. 

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