The transformation of carbon-hydrogen (C-H) bonds into diverse classes of carbon-carbon (C-C) and carbon-heteroatom (C-X) bonds is a cornerstone of organic synthesis. The fascination with applying C-H activation in complex molecule synthesis stems from the age-old notion that C-H bonds are dormant synthetic equivalents of various active functional groups. The renowned metal-catalyzed cross-coupling reactions of aryl halides and aryl-metal derivatives including boronic acids (Suzuki), organosilanes (Stille), Oragnosiloxanes (Hiyama), Organozinc compounds (Negishi), Alkynes (Sonagashira) and Olefins (Heck) have been tremendously emerged in the realm of synthetic organic chemistry. Regioselectivity is one of the vital issues in C-H bond functionalization because organic molecules can contain a wide variety of C-H bonds. A daunting challenge is imposed by the innate inertness of C-H bonds of a given substrate. Directing groups (DG)-assisted transition metal catalyzed C-H activation has proven a successful strategy for regioselective C-H functionalization in a general and predictable manner. The use of directing groups can largely overcome the issue of regio-control by allowing the catalyst to come into proximity with the targeted C-H bonds.
This project was done with the help of one of the 5th year PhD members in the lab. They had already started the project and I joined in between. The project was divided into 2 steps: Preparation of the directing groups and substrate and the other was the preparation of alkynylated source. My internship mainly focused on the synthesis of substrates and it’s optimization. In two months of internship I was able to synthesize 15 substrates and alkynylated sources but the coupling thing was left to be done which was then continued by the other students. In the organic synthetic lab it’s most important to set the reactions which I was familiar with because of my previous internships.
The substrates were purified with the help of column chromatography at each step and then the next reaction was put up. The preparation of substrate was a 2-3 step process. And at each step NMR samples were submitted to check the purity of the desired product.
During my internship, I have extensively done column chromatography to achieve the highest purity of the compound to proceed further. I got to learn about NMR data interpretation, Glove Box settings, and the most importantly HPLC for optimization results.
This work was done under the guidance of Prof. Debabrata Maiti at IIT, Bombay in the summer of 2019.
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