Background and overview[1]
(R)-3,3′-Bis(4-nitrophenyl)-1,1′-binaphthol phosphate is a chiral binaphthol-phosphate derivative that can be used as a catalyst. Asymmetric synthesis reactions such as asymmetric Mannich-type reactions, asymmetric hydrophosphorylation reactions, and asymmetric aza-Diels-Adel reactions.
Preparation[1]
1) Add (R)-3,3′-bis(dihydroxyborane)-2,2′-dimethoxy-1,1′-binaphthyl (4mmol) into a three-necked eggplant-shaped flask. , barium hydroxide 8 hydrate (12mmol), Pd(PPh3)4 (0.28mmol), 24ml of 1,4-dioxane, and 8ml of water and stir. 1-Bromo-4-nitrobenzene (10 mmol) was added dropwise to the solution, and the photoinitiator flow was returned to the solution for 25 hours. Then, 1,4-dioxane was distilled off under reduced pressure, dichloromethane was added, washed with 1M hydrochloric acid and saturated sodium chloride aqueous solution, and dehydrated with anhydrous sodium sulfate. Add the above product and 100 ml of methylene chloride into a three-neck eggplant-shaped flask. After cooling to 0°C, add BBr3 (18 mmol, 1 molar concentration methylene chloride soluble slurry manufacturer’s solution) dropwise. After the dropwise addition was completed, the mixture was stirred at room temperature for 8.5 hours, then cooled to 0°C again, and 120 ml of water was added to stop the reaction. Wash with water and saturated sodium chloride aqueous solution, dehydrate with anhydrous sodium sulfate, and then distill off the solvent under reduced pressure. The residue was purified using column chromatography (hexane:ethyl acetate=5:1) to obtain (R)-3,3′-bis(4-nitrophenyl)-1,1′-binaphthol ( Yield 82%).
2) Add (R)-3,3′-bis(4-nitrophenyl)-1,1′-binaphthol (1mmol) and 1.4ml of pyridine into a two-necked eggplant-shaped flask, and use 3 POCl3 (1.4mmol) was added dropwise over a period of minutes, and stirred at room temperature for 2 hours. Water (150 μl) was added to the reaction solution, and the mixture was further stirred for 30 minutes. Then, pyridine was distilled off from the reaction liquid under reduced pressure. Subsequently, 6M hydrochloric acid (7 ml) was added and the mixture was refluxed for 2 hours. This was cooled and purified using silica gel column chromatography containing triethylamine, and a free form was prepared using 6M hydrochloric acid. After dissolving it in a small amount of methylene chloride, n-hexane was added to precipitate it to obtain (R)-3,3′-bis(4-nitrophenyl)-1,1′-binaphthol phosphate ( Yield 62%).
1H-NMR (MHz, CDCl3)δ=8.01 (d, 2H, J=8.2Hz), 7.97 (s, 2H), 7.92 ( d, 4H, J = 8.1Hz), 7.60-7.55 (m, 6H), 7.46-7.21 (m, 4H).
