trans-4,4'-Dimethoxy (CAS NO.: ), which is also known as , 4,4'-dimethoxy-, could be produced through the following synthetic routes.

A solution of 100 mg. (0.41 mmole) of 4,4'-dimethoxybibenzyl in 1.5 ml. of anhydrous dioxane was placed in a 10-ml. round-bottomed flask. To this was added 103 mg. (0.45 mmole) of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) dissolved in 1.5 ml. of anhydrous dioxane. The flask was fitted with a reflux condenser and heated in an oil bath at 105° for 18 hours. The solution, which was initially deep green, became pale yellow as the hydroquinone crystallized out. The mixture was cooled, and the solid was filtered off. It was washed with 1 ml. of warm benzene followed by 6 ml. of warm chloroform, and dried at 100° to give 95 mg. (91%) of pure 2,3-dichloro-5,6-dicyanohydroquinone. The filtrate and washings were combined and evaporated under reduced pressure. The semisolid residue was dissolved in 5 ml. of ethyl acetate and passed through a short column of neutral alumina (2.0 g.). The column was eluted with 100 ml. of ethyl acetate. Evaporation of the solvent under reduced pressure left the crude product, which was recrystallized from 35 ml. of ethanol to give 82–84 mg. (83–85%) of trans-4,4'-dimethoxystilbene as colorless plates, m.p. 212–213.5°.