2092-49-1

121-33-5

2092-49-1

General procedure for the synthesis of 6,6'-dihydroxy-5,5'-dimethoxy-(1,1'-biphenyl)-3,3'-dicarboxaldehyde from vanillin: 5 g of vanillin (33 mmol, purchased from Wako Pure Chemical Industries, Ltd.) was dissolved in 200 ml of ion-exchanger water preheated to 80 °C. To this solution, 200 mg (0.72 mmol) of iron sulfate (purchased from Wako Pure Chemical Industries, Ltd.) and 5 g (19 mmol) of potassium peroxydisulfate (purchased from Wako Pure Chemical Industries, Ltd.) were sequentially added, followed by heating and refluxing for 1 hr at 120 °C. Upon completion of the reaction, unreacted vanillin was removed by thermal filtration to afford intermediate (a1) in 97% yield.