Dichloromethane → 1,1,2,4,4,6-Hexamethyl-1,2,3,4-tetrahydronaphthalene

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The starting material 1,1,2,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene is prepared as follows. A 100 ml four-necked round bottom flask is charged with 1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene (HMT) (20 g) and dichloromethane (32.6 g) and cooled to 0° C. with a dry ice/isopropanol bath. To the flask is then added, with stirring, anhydrous AlCl3 (2.507 g). The temperature of the flask is maintained between about 0° C. and 10° C. while the reaction is allowed to proceed for about 2.5 hrs. The reaction is then quenched with ice water (25 ml), and the resultant product washed with deionized water. The aqueous layer is extracted twice with ether, the organics are combined, dried over K2CO3 and rotoevaporated to yield a crude product (18.26 g) containing 37.22 weight percent of a mixture of 1,1,2,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene, HMT, 1,1,3,5-tetramethyl-3-isopropylindane and 1,3,3,5-tetramethyl-1-isopropylindane. The indanes are removed from the mixture by preparative gas chromatography. The desired compound, 1,1,2,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene, is then separated from HMT using a vacuum spinning band fractional distillation apparatus.

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