|M.Sc Student||Kulbitski Kseniya|
|Subject||Iodo-Decarboxylation Processes Induced by N-I Compounds|
|Department||Department of Chemistry||Supervisor||Professor Mark Gandelman|
|Full Thesis text|
New synthetic efficient and robust methodology for synthesis of organo-iodine compounds from carboxylic acids via iodo-decarboxylation process was developed. Organo-iodine compounds have found wide use in many areas of chemistry and proved to be versatile starting materials in many applications. Especially, transition metal-catalyzed coupling reactions (Ullmann, Heck, Suzuki, etc.) use aliphatic and aromatic organo-iodine compounds in homo- and cross- coupling reactions. There are several synthetic ways to obtain organo-iodine compounds: (1) halo exchange; (2) use of alcohols as starting material or (3) iodo-decarboxylation of carboxylic acid. This work focused on use of carboxylic acids in synthesis of organo-iodine compounds. Over the years numerous methods of iodo-decarboxylation were developed. Most popular between them are: (1) Hunsdiecker reaction using silver salts of carboxylic acids or mercury reagents; (2) Barton reaction, utilize Barton reagent, both methods are limited to aliphatic carboxylic acids; (3) Suarez reaction, using a strong oxidizing reagent (diacetoxyiodo)benzene and thus being a very sensitive method.
The goal of this work was to develop a new method of iodo-decarboxylation of carboxylic acids without use of heavy metals, exotic reagents or strong oxidizers. For this purpose the N-I reagents were chosen, namely N-iodosuccinimide (NIS) and 1,3-diiodo-5,5-dimethylhydantoin (DIH), as those compounds are known to be iodination reagents in organic chemistry, and the low energy of nitrogen-iodine bond allows radical initiation of decarboxylation process.
After development and optimizations, the method proved successful for both aliphatic and aromatic carboxylic acids. Our methodology gives high yields of desired product in the case of primary, secondary, and tertiary aliphatic carboxylic acids, using DIH or NIS. Iodo-decarboxylation of aromatic carboxylic acids is more challenging and additional studies are required to extend a scope. In general the methodology is selective and efficient and runs under very robust reaction conditions. Workup of the reaction mixture with aq. NaHSO3 and aq. NaHCO3 gives iodination product in organic phase and all by-products in aqueous phase. Remarkably, hydantoin accumulating in aqueous phase is biodegradable. Initial studies of the reaction mechanism indicate an involvement of radical process, initiated by irradiation or heat.