Thiosemicarbazones (TSCs) are a class of compounds with antibacterial, antifungal, and antiviral properties. Recently, they have been found to be useful in the development of antitumor drugs, making them a topic of extreme interest. Some TSCs are also known to inhibit the enzyme tyrosinase, which is responsible for the browning that occurs in damaged plants. The purpose of this project was to synthesize thiosemicarbazones using green chemistry methods, as opposed to traditional, less benign methods. Green chemistry focuses on the development of products and processes that minimize the use and production of hazardous materials. The traditional methods for synthesizing these compounds required reflux in organic solvent, usually methanol or ethanol, with acid catalyst for several hours. These traditional solvents are flammable and have other adverse health effects. Our greener method uses mostly water containing some lactic acid as the solvent. Lactic acid is an additive and preservative for food products, and is found naturally in many foods, especially dairy products. Our aqueous system is a safer alternative than the traditional solvents. The reactions in our greener method require no reflux, are complete in less than 15 minutes, and result in good to excellent purities and yields without recrystallization. A total of 18 thiosemicarbazones have been made thus far using this method. This synthesis has been class tested in two courses: second-semester organic chemistry with analysis by NMR and a one-semester introductory organic chemistry course with analysis by a simple fruit and vegetable browning assay our group developed.

Greener synthesis of thiosemicarbazones

249th National Meeting (2015)

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