(R)-3,3'-Bis(3,5-bis(trifluoromethyl)pH&

Synthesis

In a two-necked flask, (R)-3,3'-bis(3,5-bistrifluoromethoxyphenyl)-1,1'-bi-(2-naphthol) (1.91 mmol) and pyridine (7.8 mmol) were added. Phosphoryl chloride (2.69 mmol) was added dropwise over 7 minutes at room temperature, followed by stirring for 2 hours. The mixture was then heated to reflux for 1 hour. The reaction mixture was cooled to room temperature, and distilled water (1.6 ml) was added dropwise. The mixture was then heated to reflux for 1.5 hours.

Subsequently, the mixture was cooled to room temperature, and pyridine was removed by vacuum distillation. 6M hydrochloric acid (15 ml) was added dropwise, followed by reflux for 2 hours. The reaction solution was cooled to 0°C, filtered, and the filtrate was washed with water and dried. Recrystallization with dichloromethane/n-hexane was performed, but the crude product still contained impurities. Therefore, it was dissolved in ethanol and reprecipitated with 6 equivalents of hydrochloric acid to give (R)-3,3'-Bis[3,5-bis(trifluoromethyl)phenyl]-1,1'-binapthyl-2,2'-diyl hydrogenphosphate (0.9 g, 1.14 mM, 73%).

Uses

As a chiral Bronsted acid, BINOL- derived cyclic phosphoric acid (such as Akiyama chiral Bronsted acid) was also shown to be an efficient catalyst for the hydrophosphonylation of aldimines at room temperature.

General Description

(R)-3,3′-Bis[3,5-bis(trifluoromethyl)phenyl]-1,1′-binaphthyl-2,2′-diyl hydrogenphosphate is a BINOL-based chiral phosphoric acid, which can efficiently catalyze the nucleophilic addition to imine substrates. [BINOL=1,1′-bi-2-naphthol]