2,2',3,3'-Tetrahydro-1,1'-spirobi[1H-indene]-7,7'-diol

223137-81-3

223137-87-9

The general procedure for the synthesis of 2,2',3,3'-tetrahydro-1,1'-spirobi[1H-indene]-7,7'-diol from the compound (CAS: 223137-81-3) was as follows: 8.00 g of tetrabutylammonium bromide was added to the above mentioned white powder, followed by the addition of 300.00 mL of an aqueous 48% hydrogen bromide solution. The reaction mixture was placed in an oil bath at 105°C and reacted overnight. After cooling, 500.00 mL of deionized water was added followed by 500.00 mL of dichloromethane and stirred for 30 minutes. The organic phase was separated and washed sequentially with 500.00 mL of deionized water, 500.00 mL of saturated aqueous sodium bicarbonate and 500.00 mL of saturated brine. The organic phase was concentrated to give a pink powder. The powder was recrystallized with a mixed solvent of petroleum ether/ethyl acetate (8:2, v/v) to give 57 g of white powder in 45% overall yield. In this method, 48% aqueous HBr solution was used as the demethylation reagent, which is easy to obtain and store, and the reaction conditions are mild without the need for very low or high temperatures, and the yield is higher than that of other methods. The purification of the intermediate and the final product was accomplished by recrystallization, avoiding the more costly column chromatography separation and purification method that produces a large amount of solid waste, and at the same time significantly reducing the amount of solvent used.