Dihydroresorcinol

In a 2-1. flask fitted with a total-reflux, variable-take-off distillation head is placed a solution of 53 g. (0.472 mole) of dihydroresorcinol (Note 1), 2.3 g. of -toluenesulfonic acid monohydrate and 250 ml. of absolute ethanol in 900 ml. of benzene. The mixture is heated to boiling and the azeotrope composed of benzene, alcohol, and water is removed at the rate of 100 ml. per hour. When the temperature of the distilling vapor reaches 78° (Note 2), the distillation is stopped and the residual solution is washed with four 100-ml. portions of 10% aqueous sodium hydroxide which have been saturated with sodium chloride. The resulting organic solution is washed with successive 50-ml. portions of water until the aqueous washings are neutral and then concentrated under reduced pressure. The residual liquid is distilled under reduced pressure. The yield of 3-ethoxy-2-cyclohexenone (Note 3), b.p. 66-68.5°/0.4 mm. or 115-121°/11 mm., Mq 1.5015, is 46.6-49.9 g. (70-75%). 

The preparation of dihydroresorcinol was described in an earlier volume of this series. ... 

Ethoxy-2-cyclohexenone has been prepared by reaction of the silver salt of dihydroresorcinol with ethyl iodide and by the reaction of dihydroresorcinol with ethyl orthoformate, ethanol and sulfuric acid." The acid-catalyzed reaction of dihydroresorcinol with ethanol in benzene solution utilized in this preparation is patterned after the procedure of Frank and Hall. ... 

Dicarbomethoxyacetylene has also been added to the pyrrolidine enamine derivative of acetylacetone, demonstrating a new synthesis of phthalic esters (345). A 3-acylpyridine synthesis was achieved by the addition of an acetylenic aldehyde to the vinylogous amide derived from ammonia and dihydroresorcinol (346). 

Palladium may not be preferred for dihydric aromatics. Dihydroresorcinol was obtained in 87% yield by alkaline hydrogenation of resorcinol over 5% Rh-on-C (65) and in only 50-60% yield over Pd-on-C 15). A 77% yield of the dione was obtained by alkaline hydrogenation of 3,5-dihydroxyphenylacetic acid over a 10% loading of 5% Rh-on-AljOj at 55"C and 55 psig (39a). 

Dihydroresorcinol, 41, 56 methylation of, 41, 56 reaction with ethanol to yield 3 ethoxy-2-cydohexenone, 40, 41... 

Hydrogenation, of gallic add with rhodium-alumina catalyst, 43, 62 of resorcinol to dihydroresorcinol, 41,56 Hydrogen peroxide, and formic acid, with indene, 41, 53 in oxidation of benzoic add to peroxy-benzoic add, 43, 93 in oxidation of ieri-butyl alcohol to a,a/r, a -tetramcthyltetra-methylene glycol, 40, 90 in oxidation of teri-butylamine to a,<, a, a -tetramethyltetra-methylenediamine, 40, 92 in oxidation of Crystal Violet, 41, 2, 3—4... 

Methyl hydrogen sebecate, 41, 34 Kolbe electrolysis of, 41, 33 1-Methylindole,40, 68 Methyl iodide, methylation of dihydroresorcinol with, 41, 57 Methyl isocyanide, 41, 15 Methyl 4-mcthyl-4-nitrovalerate, hydrolysis to acid, 41, 24 N-Methyl-N-nitrosoterephthalamide, preparation of diazomethane from, 41, 16... 

A2EPIN-2 -ONE, 44, 41 Dihydropyran, purification of, 41, 77 reaction with dichlorocarbene, 41, 76 Dihydroresorcinol, 41,56 methylation of, 41, 56 reaction with ethanol to yield 3-ethoxy-2-cyclohexenone, 40, 41 Dihydroresorcinoi. monoethyl ether, 40,41... 

Methylindole, 40, 68 a-Methylindole-3-acetic acid, 44, 66 Methyl iodide, methylation of dihydroresorcinol with, 41, 57... 

A roundabout route is used to prepare tetrahydroquinolines with reduced carbocyclic rings since direct reduction, as noted above, adds hydrogen to the heterocyclic ring. The key reaction in this scheme involves a variant of the Hantzsch pyridine synthesis. Condensation of the imine (37-1) from dihydroresorcinol with ethoxymethylenepropionaldehyde (37-2) can be envisaged as proceeding through... 

Ji-Toluenesulfonic acid, as catalyst, for formation of enamines, 41, 65 for reaction of dihydroresorcinol with ethanol, 40, 41... 

A variation consists in starting from dihydroresorcinol (or its dimethyl ether) and from the diacetal of compound 287 thus, evodone (289, R3 = R6 = CH3), a natural substance, has been obtained (as the racemate) by ring closure (with HC1) of compound 290.693 Similarly, the... 

Halohydrins of type 370 (X = halogen) with piperidine or morpholine give compound 371.821 Compound 372 (obtained by tetracyanoalkyl-ation of dihydroresorcinol) is ring contracted by 10% NaOH to com-... 

In a closely related reaction, heating the trimethylamine salt of the condensation product of dihydroresorcinol and 5-ethoxymethylene-3-methylrhodanine with aqueous alkali affords 4,5,6,7-tetrahydro-benzo[6]thiophen-4-one-2-carboxylic acid (92), via the intermediate (91).846... 

Dimethyl-dihydroresorcinol has always been made from mesityl oxide and malonic ester. The procedure given above is that of Vorlander.1... 

The apparatus is allowed to cool to room temperature, the pressure is released, and the catalyst is removed by filtration. The filtrate is made acid to Congo red with concentrated hydrochloric add, and the solution is cooled to 0° in an ice-salt bath and held at that temperature for 30 minutes before filtration. The dihydroresorcinol which crystallizes is separated by filtration and dried 50-60 g. of crude dry product containing sodium chloride is obtained. 

Dihydroresorcinol is unstable it can be stored only a short time. If it is not used immediately, it should be stored under an inert gas in a brown bottle in a refrigerator. 

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... 

Resorcinol as mono sodium salt is selectively hydrogenated over Ni-kieselguhr to the sodium salt of dihydroresorcinol, which on acidification gives cyclohexane-1,3-dione in high yield (eq. 11.27).141,142 The same selective hydrogenation [10 g (0.091... 

The crude dihydroresorcinol is dissolved in 125-150 ml. of hot benzene, filtered to remove the sodium chloride, and allowed to crystallize. The solid is separated by filtration and dried overnight in a vacuum desiccator. The product melts at 103-104° and weighs 48-53 g. (85-95%) (Note 4). 

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