Trimethyl-2, 4-cyclohexadienone

Deceased October 24, 1965 formerly at University of Marburg, Marburg, Germany. 

Submitted by David Y. Curtin and Allan R. Stein 1 Checked by William G. Dauben and Joel W. Rosenthal 

Lithium 2,6-dimetkylpkenoxide. In a 300-ml. flask, equipped with a magnetic stirrer and a reflux condenser and flushed with nitrogen, are placed 150 ml. of toluene (freshly distilled from sodium), 1.40 g. (0.202 mole) of lithium metal (Note 1) and 25.0 g. (0.205 mole) of resublimed 2,6-dimethylphenol. The mixture 

6-Trimethyl-2,4-cyclohexadienone. In a nitrogen-filled dry box, 25.0 g. of lithium 2,6-dimethylphenoxide (0.195 mole) is transferred to an oven-dried, thick-walled Pyrex bomb tube (650 x 19 mm.). The bomb tube is stoppered with a rubber stopper fitted with a drying tube, removed from the dry box, and 75 ml. of methyl iodide (170 g., 1.20 moles) (freshly distilled from calcium hydride) is quickly pipetted into the bomb under a dry nitrogen stream. The bomb is cooled in a dry-ice bath and sealed with an oxygen torch. After warming to room temperature, the bomb is shaken to disperse the salt cake and placed in a bomb furnace which has been preheated to 135° (Note 7). 

After 36 hours the furnace is allowed to cool, the bomb is removed, cooled to dry-ice temperatures, and opened carefully as there may be residual pressure. The golden brown liquid is poured into a 200-ml. flask, and the methyl iodide is removed on a rotary evaporator (iCautionI Hood). The residue from the flask and the bomb is washed into a 500-ml. separatory funnel with 100 ml. each of ether and 1 1 solution of Claisen s alkali and water (Note 8). The funnel is shaken, and the alkali layer is removed. The ether layer is extracted four additional times with 100 ml. portions of the alkali (Note 9), washed twice with 75-ml. portions of water, once with saturated aqueous salt solution, and 

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This preparation of 2,6,6-trimethyl-2,4-cyclohexadienone is based upon the published procedure of the submitters,2 and it is the only preparation of the 2-substituted-2,4-cyclohexadienones. The simpler 6,6-dimethyl-2,4-cyclohexadienone is more conveniently prepared by the method of Alder.4... 

The photochemical rearrangements of 2,4,6-trimethyl-6-acetoxy-2,4-cyclohexadienone (Formula 105) are of special interest. Irradiation of Formula 105 in ether containing a good nucleophile such as cyclohexyl amine gives the expected a, -unsaturated amide (Formula 106) (48). In sharp contrast to expectation, irradiation of Formula 105 in ether con-... 

Irradiation of 2,4,6-trimethyl-6-allyl-2,4-cyclohexadienone (Formula 113) in ether containing cyclohexyl amine gives the expected ctfi-... 

A stereospecific acetoxyl group migration reminiscent of that noted in the irradiation of 2,4,6-trimethyl-6-acetoxy-2,4-cyclohexadienone (see Sec. IIB,1) is observed in the irradiation of 7-ketocholesteryl acetate (Formula 205). Irradiation of Formula 205 gives two products (Formulas... 

TABLE VII lists the results. In the absence of CyD, the allylation at the ortho position predominantly occurs. a-CyD and 3-CyD improve the yield and selectivity of the para allylation [10]. The modification of a-CyD was carried out by N-methyl formamidation of six primary hydroxyl groups of a-CyD. The modified a-CyD gives 4-allyl-2,4,6-trimethyl 2,5-cyclohexadienone in 85% yield with 100% selectivity. 

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