Saturday, September 28, 2019

Asymmetric Synthesis Essay Example | Topics and Well Written Essays - 1000 words

Asymmetric Synthesis - Essay Example Hence, it is undeniably interesting to study the catalytic asymmetric synthesis of cinchona alkaloids , which have also been helpful in man's daily living. This includes its role in the production of food flavorings and medicines for different ailments like malaria. Additionally, the popularity of cinchona alkaloids over the years is also because of its qualifications in the three primary criteria of catalysts, which are as follows: 1) the diversity of reactions that the catalyst can trigger; 2) the accessibility of both enantiomeric antipodes of the catalyst at an affordable cost; and 3) the stability of the catalyst. The research aims to study the catalytic asymmetric synthesis of the popular two pairs of cinchona alkaloids which are enantiomeric in nature: cinchonine and cinchonidine, and; quinine and quinidine. The researcher aims to study the two pairs by isolating them through extraction of the bark of the cinchona tree; a native of tropical regions. Due to their widespread use, all four members are readily available in large quantities from most chemical suppliers. Furthermore, before conducting several experiments for the research, the researcher will gather enough materials documenting the history of cinchona alkaloids. ... erature section of the research, which will include information about cinchona alkaloids from one of the earliest uses of cinchona alkaloids in asymmetric catalysis which was demonstrated by Pracejus in the 1960's to catalyze the asymmetric alcoholysis of ketenes (Pracejus, 1964) to its modern uses. Moreover, the study's related literature will consist of theories proposed about the asymmetric synthesis of cinchona alkaloids by chemists of different ages. One interesting theory which will contribute to the study of the alkaloid's catalytic asymmetric synthesis is that the alcohol is activated via a hydrogen bond with the tertiary amine of benzoylquinine. Addition of the alcohol to the ketene is followed by quenching of the resultant enolate by the chiral ammonium salt. The resultant esters are isolated in up to 76% enantiomeric excess. The research will strive to replicate the experiments conducted to support this theory. Also, with the proliferation of recent publications studying cinchona-ketene systems for asymmetric synthesis (Blake, 2001), the study will investigate different assumptions about the asymmetry in the synthesis of cinchona alkaloids. One of the most noticeable of these recent publications which the researcher intends to focus is Lectka's -halogenation of acid chlorides (Wack, 2001). Lectka stated that the benzoylquinine-ketene system reacts with quinone based electrophilic halogenating reagents to yield activated -halogenated esters with enantioselectivities as high as 99%, and with good yields. The study will try to prove this through catalytic asymmetric fluorination, where cinchona derivatives have already been used, though only stoichiometrically (Muiz, 2001). However, despite the efforts to base certain experiments upon previous studies, the

No comments:

Post a Comment

Note: Only a member of this blog may post a comment.