Resorcinol: carboxylation

Resorcinol carboxylation with carbon dioxide leads to a mixture of 2,4-dihydroxyben2oic acid [89-86-1] (26) and 2,6-dihydroxyben2oic acid [303-07-1] (27) (116). The condensation of resorcinol with chloroform under basic conditions, in the presence of cyclodextrins, leads exclusively to 2,4-dihydroxyben2aldehyde [95-01-2] (28) (117). Finally, the synthesis of l,3-bis(2-hydroxyethoxy)ben2ene [102-40-9] (29) has been described with ethylene glycol carbonate in basic medium (118), in the presence of phosphines (119). Ethylene oxide, instead of ethyl glycol carbonate, can also be used (120). 

The facile decarboxylation of resorcinol carboxylic acids and notably of orsellinic acids in alkaline solution poses a problem during their syntheses in high yield. For this reason the synthesis of alkoxycarbonyl derivatives is usually adopted followed by acidic hydrolysis. The removal of the protective acetyl groups in the compound shown was effected preferentially without hydrolysis of the ester group. Methyl 2,6-diacetoxybenzoate in toluene saturated with water when add to a catalyst (prepared from 4-toluenesulphonic acid monohydrate and silica gel) and stirr at 86°C during 6 hours, afford methyl... 

Mechoulam R, Ben-Zvi Z, Carboxylation of resorcinols with methyl magnesium carbonate. Synthesis of cannabinoid acids, Chem Commun 343—344, 1969. 

As regards organic contaminants, leachates from semi-coke contain compounds such as phenols, for example, cresols, resorcinols, and xylenols, which occur at mg/L concentrations. Indeed, Kahru et al. (2002) found total phenols at concentrations up to 380 mg/L in semi-coke dump leachates. Phenols also volatilize from such leachates, depending on temperature and pH (Kundel Liblik 2000). Atmospheric phenol concentrations of 4-50 xg/m3 have been observed in the proximity of leachate ponds (Koel 1999). Generally, aliphatic hydrocarbons, carboxylic acids, and organo-nitro and organo-sulpho compounds do not occur at elevated concentrations in leachates from Estonian semi-coke (Koel 1999). 

The use of triethyl orthobut-2-ynoate, MeC=CC(OEt)3, yields 4-methylcoumarins, whilst with dimethyl butynedioate, resorcinol affords methyl coumarin-4-carboxylate in a reaction catalyzed by zinc chloride (69MI22400). The potential elaboration of this approach to coumarins is quite apparent. 

Exercise 26-7 1,3-Benzenediol (resorcinol) can be converted to a carboxylic acid with carbon dioxide and alkali. Would you expect 1,3-benzenediol to react more, or less, readily than benzenol Why Which is the most likely point of monosubstitution Explain. 

The carboxylation reaction is particularly facile with di- and tri-hydric phenols. Thus 2,4-dihydroxybenzoic acid (Expt 6.156) is readily obtained by passing carbon dioxide through a boiling aqueous solution of the potassium or sodium salt of resorcinol. 

Reformatsky reaction, 511, 599 Reissert compounds, 150 Resistomycin, 450 Resorcinols, 66, 460-461 Retinal, 120 Retrolactonization, 17 Rhodium(ll) carboxylates, 458-460 Rhodium catalysts, 460 Rhodium(III) chloride, 460-461 Rhodium(III) porphyrins, 461-462 Rifamyem S, 133, 134 Ruthenium(III) chloride, 462 Ruthenium tetroxide, 462-463... 

These compounds can condense and cyclize with resorcinol or substituted 3-aminophenols. Nucleophilic substitution of chlorine by amines leads to xanthene dyes which contain a sulfonic acid group [10] or hydrogen [11] instead of the carboxyl group. 

First, 1 2 metal complexes of (mainly mono-) azo dyes, without sulfonic or carboxylic acid groups, and trivalent metals (see Section 3.11). The metals are preferably chromium and cobalt nickel, manganese, iron, or aluminum are of lesser importance. Diazo components are mainly chloro- and nitroaminophenols or amino-phenol sulfonamides coupling components are (3-naphthol, resorcinol, and 1-phe-nyl-3-methyl-5-pyrazolone. Formation of a complex from an azo dye and a metal salt generally takes place in the presence of organic solvents, such as alcohols, pyridine, or formamide. An example is C.I. Solvent Red 8, 12715 [33270-70-1] (1). 

Dihydroresorcinol has been prepared by the reduction of resorcinol with sodium amalgam,2 by reduction of hydroxyhydroqui-none or its carboxylic acid with sodium amalgam,3 by hydrolysis of its dioxime,4 or by cyclization of ethyl y-acetylbutyrate.s The present method of preparation is essentially that of Klingenfuss.6... 

Phenols and Enolizable Keto Compounds. These compounds are coupled in alkaline (soda) solution as a rule. If the coupler is a sulfonic or carboxylic acid, or is soluble in water (e.g., resorcinol), it is dissolved directly in the required amount of soda solution. In other cases, the coupler is dissolved in the equivalent amount of dilute sodium hydroxide solution and the recaustic soda for complete solution in such cases, no more is used than is absolutely required. (Solution of the 2-hydroxyl-3-naphthoic acid arylides is greatly assisted by the addition of alcohol. In many cases, no other method of dissolving the coupler is known.) An unnecessarily large excess of alkali is to be avoided, except in special cases, since such an excess rapidly decomposes the diazo compound. It is desirable to use that amount of soda which will be converted to bicarbonate by the acid of... 

More active aromatic compounds, such as resorcinol and a-naphthol, are carboxylated in excellent yields by heating their alkali salts with carbon dioxide (Kolbe reaction). The carboxyl group of salicylic acid migrates to the para position when this compound is heated to 240° with potassium carbonate the p-hydroxybenzoic acid is obtained in 80% yield. ... 

When more than one hydroxyl group is substituted in the ring of an aromatic acid there will result poly-phenol acids i.e., poly-hydroxy acids. The poly-hydroxy benzoic acids, which include the most important members, bear the same relation to benzoic acid that the ordinary poly-phenols, e.g., pyrocatechinol, resorcinol, pyrogallol, etc. (p. 617), do to benzene. They may also be considered as carboxyl substitution products of the poly-phenols. 

The nmr chemical shifts of alkah metal ( K, Na etc.) phenoxide moved to down field upon formation of the complex, [ phenoxide-M CO2] with carbon dioxide in the Kolbe-Schmitt reaction. The complex formed under pressure of carbon dioxide showed more increments in weights and chemical shifts, as much as 0.72 ppm of (5 paia of potassium phenoxide at 5 MPa. The kinetic studies on the carboxylation of resorcinol in aqueous hydrogencarbonates with carbon dioxide revealed an equilibrium between resorcinol and the product or resorcylic acid. 

The Kolbe-Schmitt reaction[l] has long history related with aspirin and has been a name reaction used for the longest period in an industrial process. While the demand for the manufacturing aromatic hydroxycarboxyhc acids is still successively coming out today with a number of patents, the mechanism of the reaction has remained unsolved. The present nmr spectroscopic studies have proved a [substrate CO2] complex or an intermediate prior to the formation of carboxyhc acids. Another puzzling question about the unstable complex even to moisture, is why the carboxylation of polyhydroxybenzenes, such as resorcinol, should proceed in aqueous solutions. Herein also reported are kinetic studies on the carboxylation of resorcinol in aqueous solutions of alkali hydrogencarbonates. 

The Kolbe-Schmitt reactions of polyhydroxy phenols such as resorcinol, pyrogallol and phloroglucinol are exceptionally carried out in aqueous solution.[6] Any explanation has not yet been given to the reason of the exception. Kinetic studies on the carboxylation of resorcinol (ROH) with hydrogencarbonate (KHCO-O were carried out in aqueous solutions. 

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