Ethoxy-2-cyclohexenone

The preparation of 3-ethoxy-2-cyclohexenone is described elsewhere in this volume. ... 

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%). 

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. ... 

Ethoxy-2-cyclohexenone is a useful intermediate in the synthesis of certain cyclohexenones. The reduction of 3-ethoxy-2-cyclohexenone with lithium aluminum hydride followed by hydrolysis and dehydration of the reduction product yields 2-cyclo-hexenone. Similarly, the reaction of 3-ethoxy-2-cyclohexenone with Grignard reagents followed by hydrolysis and dehydration of the addition product affords a variety of 3-substituted 2-cyclo-hexenones. ... 

Lithium aluminum hydride, in reduction of 3-ethoxy-2-cyclohexenone to 2-cyclohexenone, 40, 14 Lithium ethoxide in condensation of benzaldehyde with tripbenylcin-namylphosphonium chloride to form 1,4-diphenyl-l, 3-butadiene,... 

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... 

Acylation reactions can also be greatly improved in this way, with t-alkyl- or sec-alkyl-manganese reagents reacting with acid chlorides in excellent yields [123]. The related addition-elimination to 3-ethoxy-2-cyclohexenone is also improved, resulting after acidic aqueous workup in 3-methyl-2-cyclohexenone [125]. The perilla-ketone 126 was prepared in an improved yield using copper(I) catalysis (Scheme 2.58) [129]. 

Ethanol, 2-nitro-, 41, 67 conversion to nitroethylene, 41, 71 Ether, tert-butyl phenyl, 41, 91 Etherification of cholestanol, 41, 9 with diazomethane, 41, 9 3-Ethoxy-2-cyclohexenone, 40, 41 reduction to 2-cyclohexenone, 40, 14... 

Fig. 10.37. Preparation of cyclohexenones through addition of a Grignard- or organo-lithium compound to 3-ethoxy-2-cyclohexenone, which is inevitably followed by an El elimination—even if workup of the reaction mixture is performed with a weak acid.

Dihydroresorcinol, 41, S6 methylation of, 41, 56 reaction with ethanol to yield 3-ethoxy-2-cyclohexenone, 40, 41... 

Lithium aluminum hydride in reduction of 3-ethoxy-2-cyclohexenone to... 

Bromo-m-terphenyl in an equal mixture of ether and benzene added at 10° to a slight excess of n-butyllithium in ether, kept an additional 20 min. at 10°, 3-ethoxy-2-cyclohexenone in ether added, stirred 30 min., and decomposed with dil. H2SO4 -> 3-(4-m-terphenyl)-2-cyclohexenone. Y 88%.—This is a step in a polyphenyl synthesis. F. e. and steps s. G. F. Woods et al.. Am. Soc. 82, 5227 (1960) branched polyphenyls s. 82, 5232. 

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