Cinchona benefits

As reviewed in this chapter, cinchona alkaloids have played a crucial role in the development of asymmetric phase-transfer catalysis since its advent, and today constitute a privileged structural motif that may be widely utilized for the design of new chiral quaternary ammonium salts. These benefits are due not only to the... 

Interestingly, the molecular structure of the 2,7-naphthyl catalysts 39 and 40 markedly resembles that of the 1,3-phenyl catalysts 37 and 38, respectively the only difference is the distance between the two cinchona alkaloid units. The naphthalene linker is about 2.4 A longer than the benzene linker. The Park-Jew group proposed that the reason for the higher enantioselectivity of the 2,7-naphthyl catalyst was that the 2,7-naphthalene linker might confer a spatial benefit to form a more favorable conformation by decreasing the steric hindrance between the two cinchona units compared to that in the 1,3-benzene linker. 

From the practical point of view, 9-O-cinchona carbamates also offer additional benefits they are stable in a broad range of pH (3-10) and can be readily obtained in a one-step reaction of a cinchona alkaloid with an appropriate isocyanate. 

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