p-Toluenesulfonic acid → (4-Methoxy-2-methylphenyl)(4-methoxyphenyl)methanone

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Reaction Steps

2-methyl-4,4'-dimethoxybenzophenone was prepared from the Friedel-Crafts reaction of 3-methyl anisole with anisoyl chloride using aluminum chloride as catalyst and hexane as the solvent. The benzophenone product (6.1 grams, 0.02 mole) was converted to the propargyl alcohol according to the procedure of Example 1, Step 2. The resulting crude oil was taken up in 150 milliliters of benzene and 2.8 grams (0.01 mole) of 2-naphthol and 0.1 grams of p-toluene sulfonic acid were added to the benzene solution. The resulting mixture was stirred at room temperature for about 30 minutes and then poured into an equal volume of 5 percent aqueous sodium hydroxide. The organic layer was washed with water and the benzene solvent removed on a rotary evaporator. The remaining crude product was subjected to column chromatography using a 1:1 mixture of chloroform and hexane as elutant. The photochromic fractions were combined and the product crystallized from a mixture of hexane and ether. The product had a melting range of 112-114C. Nuclear Magnetic Resonance (NMR) analysis of the product confirmed it to be, 3(2-methyl-4-methoxyphenyl)-3-(4methoxyphenyl)-3H-naphtho-[2,1-b]pyran.

Provenance & Evidence