Azacrown ether-type quaternary ammonium

SYNTHESIS OF THE AZACROWN ETHER-TYPE QUATERNARY AMMONIUM SALT... 

To the precipitate was added dichloromethane, and then the combined organic extracts were filtered and concentrated in vacuo to afford the corresponding azacrown ether-type quaternary ammonium salt (0.27 g, 85%) as a light brown crystalline solid. The purity of the cmde product is high enough to be used in the catalysis experiments, m.p. 118-119 °C [a]p 71 (c= 1.0, CHCI3). 

ASYMMETRIC EPOXIDATION OF (E)-CHALCONE CATALYZED BY THE AZACROWN ETHER-TYPE QUATERNARY AMMONIUM SALT AS CHIRAL PTC... 

Azacrown ether-type quaternary ammonium salt (53.2 mg, 0.050 mmol)... 

A mixture of ( )-chalcone (104.1 mg, 0.50 mmol), the azacrown ether-type quaternary ammonium salt (53.2 mg, 0.050 mmol) and toluene (1.5 mL) was placed in a 20 mL round-bottomed flask equipped with a magnetic stirrer bar. To this solution, 2 M aq. KOH (0.63 mL, 1.25 mmol) was added, and then the resultant mixture was stirred vigorously at 0°C for 10 min. 

Table 6.10 Asymmetric epoxidation of chalcones catalyzed by the azacrown ether-type quaternary ammonium salts as Chiral PTCs (see Figure 6.8).

Hori, K., Tamura, M., Tani, K., Nishiwaki, N., Ariga, M. and Tohda, Y. Asymmetric Epoxidation Catalyzed by Novel Azacrown Ether-type Chiral Quaternary Ammonium Salts under Phase-transfer Catalytic Conditions. Tetrahedron Lett. 2006, 47, 3115-3118. 

ASYMMETRIC EPOXIDATION CATALYZED BY NOVEL AZACROWN ETHER-TYPE CHIRAL QUATERNARY AMMONIUM SALTS UNDER PHASE-TRANSFER CATALYTIC CONDITIONS... 

The azacrown ether-type chiral quaternary ammonium salts as chiral PTCs are easily prepared from BINOL in four steps. Remarkably, Table 6.10 shows that the good efficiency of asymmetric epoxidation of various chalcones can be achieved by adjustment of the length of the carbon chains on the nitrogen atom in the quaternary ammonium salts. 

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