Resorcinol benzoylation

Sulfur, resorcinol, benzoyl peroxide, or salicylic acid Caut ous y use concomitant topical medications because of possible interactions with tretinoin. Significant skin irritation may result. It also is advisable to rest a patient s skin until the effects of such preparations subside before use of tretinoin is begun. 

Sulfur is used in acne medications to treat inflamed lesions (pimples). It can cause whiteheads and blackheads (comedones) if used by itself, so it is usually combined with salicylic acid, benzoyl peroxide, or resorcinol, which eliminates comedones. 

While these agents may cause less skin irritation than benzoyl peroxide or the topical retinoids, several disadvantages exist. Sulfur preparations produce an unpleasant odor when applied to the skin, while resorcinol may cause brown scaling. And although rare, the possibility of salicylism exists with continual salicylic acid use.3,12... 

Three synthetic approaches for benzopyrones have been developed that use Gly as starting material. Hippuric acid was transformed with acetic anhydride into 2-phenyl-5(4//)oxazolone or further into its 4-ethoxy-methylene derivative, then reacted with cyclic 1,3-dicarbonyI compounds (such as like dimedone) to form 100 [90LA501 92H(33)843]. On the other hand, when hippuric acid was transformed into methyl 2-benzoyl-amino-3-dimethylaminopropenoate, it reacted with resorcinol to give a 7-hydroxybenzopyrone derivative (89JHC1273). 

With this purpose, several different types of solid acid catalysts have been investigated for the acylation of aromatics, but the best performances have been obtained with medium-pore and large-pore zeolites (3-9). In general, however, the use of acylating agents other then halides, e.g., anhydrides or acids, is limited to the transformation of aromatic substrates highly activated towards electrophilic substitution. In a previous work (10), we investigated the benzoylation of resorcinol (1,3-dihydroxybenzene), catalyzed by acid clays. It was found that the reaction mechanism consists of the direct 0-benzoylation with formation of resorcinol monobenzoate, while no primary formation of the product of C-benzoylation (2,4-dihydroxybenzophenone) occurred. The latter product formed exclusively by... 

The keratolytic compounds in over-the-counter acne products are benzoyl peroxide, salicylic acid, sulphur and resorcinol. 

The best results are achieved when the skin has been prepared for 15 days beforehand see Chapter 2. If the skin has been prepared with tretinoin or alpha-hydroxy acids (AHAs), if the patient has used products (benzoyl peroxide) or techniques (scrub, or abrasion with a massage glove) that increase the permeability of the stratum corneum, the resorcinol paste should not be left on too long. 

Pyridine-catalyzed acylation of phenols using benzoyl chloride and benzoyl bromide was reported . Acylation of phenols using acetyl chloride or benzoyl chloride can be achieved using triflic acid as the catalyst in nonpolar solvents snch as methylene chloride. The role of pyridine in these reactions seems to be the intermittent formation of the benzoylpyrimidinium ions as the reactive species. The activated phenolic componnds snch as resorcinol, on the other hand, could be acylated in near-supercritical water (250-300 °C) without using any external Lewis acid catalysts (equation 47) . The equilibrium conversions in water, however, are to the extent of about 4%. Running the same reactions in neat acetic acid causes a tenfold increase in yield. 

The first step consisted of the Mitsunobu etherification of an allyl alcohol with the resorcinol monoester, which afforded 102. Cleavage of the benzoyl protecting group released the phenol, which was then attached to the solid support. One-step cleavage of the THP group and bromination was achieved with PPhs/C Br4 to furnish 103. Nucleophilic substitution of the bromide with benzylamine was followed by acylation of the secondary amine wtith N-Boc-allylglycine 104, which resulted in the precursor 105, ready for the metathesis reaction this was performed with catalyst 101 to yield the final product 106. Either 1-octene or ethene was employed to generate 101. 

The benzoylation of resorcinol to produce 2,4-dihydroxybenzo-phenone has been previously performed with benzotrichloride, which implies the coproduction of 3 mol of hydrochloric acid and consequently a large amounts of acid waste. " Alternative routes to 2,4-dihydroxyben-zophenone involve direct acylation of resorcinol with benzoyl chloride (BC) or the Hoesch reaction with benzonitrile, which also suffer from acid waste production. In a more ecoefficient approach, the reaction was performed with benzoic acid (BAC) in the presence of some solid catalysts, with a special focus on BEA zeolite (Scheme 5.9). The progress of the reaction in para-chlorotoluene is examined, and after 18 h, 2,4-dihy-droxybenzophenone (2,4-DHB) is isolated in 70% yield, together with 20% of resorcinol monobenzoate (RMB), 3% of resorcinol dibenzoate, 5% of BAC, and 2% of resorcinol. The fact that the concentration of resorcinol in the final mixture is somewhat lower than that of BAC is probably due to the preferred adsorption of the former. The process is then studied by using different substituted BACs the different conversions of 2-methyl-,... 

Bolognini, M., Cavani, F, Cimini, M., Dal Pozzo, L., Maselli, L., Venerito, D., Pizzoli, F, and Veronesi, G. 2004. An environmentally friendly s)mthesis of 2,4-dihydroxybenzophenone by the single-step O-mono-benzoylation of 1,3-dihydroxybenzene (resorcinol) and Fries rearrangement of intermediate resorcinol monobenzoate the activity of acid-treated montmorillonite clay catalysts. C. R. Chim. 7 143-150. 

Due to their reactivity towards substitution under conditions in which phenol itself is unreactive, 1-hydroxy-3-aikoxybenzenes require milder catalysts than generally employed for the former. Resorcinol monomethyl ether in benzene containing benzoyl chloride upon addition to boron trichloride (1 mole) in benzene at -lO C followed by refluxing for 10 hours and aqueous work-up at ambient temperature, afforded 2-hydroxy-4-methoxybenzophenone in 85% yield (ref.132). 

Acne is treated by gently applying a cleansing agent several times a day to the skin. Vigorous scrubbing should be avoided. In addition, the patient can administer topical anti-acne medication such as keratolytics. These include benzoyl peroxide, resorcinol, and salicylic acid that dissolves keratin, the outer layer of the epidermis. 

CAS 131-56-6 EINECS/EEINCS 205-029-4 Synonyms Benzoresorcinol 4-Benzoyl resorcinol BP1 DHBP 2,4-Dihydroxybenzophenone (2,4-Dihydroxyphenyl) phenylmethanone Methanone, (2,4-dihydroxphenyl) phenyl-ClassiTicatbn Organic benzophenone deriv. 

Benzoyloxytributylstannane. See Tributyltin benzoate o-Benzoylphenol. See 2-Hydroxybenzophenone 4-Benzoyl resorcinol. See Benzophenone-1 Benzquinamide. See Benzoguanamine Benztriazole. See 1 H-Benzotriazole... 

CAS 131-56-6 EINECS/ELINCS 205-029-4 Synonyms Benzoresorcinol 4-Benzoyl resorcinol BP1 DHBP 2,4-Dihydroxybenzophenone (2,4-Dihydroxyphenyl) phenylmethanone Methanone, (2,4-dihydroxphenyl) phenyl-Classification Organic benzophenone deriv. Empirical C13H10O3 Formula C6HsCOC6H3(OH)2 Properties Off-wh. to It. yel. cryst. solid sol. in ethanol, methanol, MEK, ethyl acetate insol. in water m.w. 214.23 m.p. 142 C b.p. 194 C (1 mm)... 

Benzoyl resorcinol. See Benzophenone-1 Benzoylstearoyl methane. See Stearoyl benzoyl methane Benzoyl superoxide. See Benzoyl peroxide... 

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. 

The catalysts required by plastics may be classified as (1) strong add catalysts (e.g., sulfuric acid, hydrochloric acid, and phosphoric acid alone or in combination with modifiers), (2) latent acid catalysts (e.g., ammonium salts of strong acids such as ammonium chloride generally useful in accelerating the setting of urea or melamine resins), (3) aldehydic catalysts (e.g., catalysts peculiar to phenol-formaldehyde and urea-formaldehyde resins such as paraformaldehyde and hexamethylenetetramine often used in urea and resorcinol adhesives), and (4) peroxide catalysts (e.g., benzoyl peroxide and dicumyl peroxide promote polymerization of polyesters through a free radical mechanism). 

One of the early methods of producing 2,4-dihydroxybenzophenone was the melting of benzoic acid or benzoyl chloride with resorcinol at a temperature of 150-160°C in the presence of anhydrous ZnCl2 [14-17], a mixture of ZnCl2 and POCI3 [25], or in the presence of BF3 [26], which serve as catalysts of the reaction ... 

As underlined in the introduction of this section, the resorcinol acylation represents a very important process. The benzoylation of resorcinol to produce 2,4-dihydroxybenzophenone, previously performed with benzotrichloride (which implies the coproduction of 3 mol of hydrochloric acid and consequently a large amounts of acid waste) [43,48,121], is carried out by using benzoic acid in the presence of HBEA zeolite (Scheme 3.17) [32,46]. 

Also obtained by reaction of benzoyl chloride with resorcinol [197],... 

Preparation by Friedel-Crafts acylation of resorcinol dimethyl ether with benzoyl chloride,... 

Preparation by reaction of benzoyl chloride with 4-methyl-resorcinol dimethyl ether in the presence of aluminium chloride in ethylene dichloride (97%) [589],... 

PrqKiration by reaction of m-(trifluOTCMnethyl) benzoyl chloride with resorcinol dimethyl ether in the presence of aluminium chloride or titanium tetrachloride in refluxing n-hexane for 8 h [239]. - Preparation by reaction of m-(trifluoromethyl)benzonitrile with m-methoxyphe-nol in the presence of aluminium chloride for 8 h at 190°, followed by hydrolysis of the ketimine so formed [77]. 

N.B. This ketone was called 2-nitro-5-benzoyl resorcinol in the paper (table 1, compound 4) [1212]. 

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