Preparation and structure of diaryliodonium salts with hydroxy and carboxylic acid groups

Abstract

Toxic transition metals are often used in organic synthesis reactions, which poses a potential hazard in their applications, especially medicinally and environmentally. A potential solution to this problem is to use trivalent iodine in place of toxic transition metals in synthesis. One class of compounds that could be specifically useful in toxic transition metal replacement is pseudo-cyclic iodonium triflate salts. This project focuses on developing the best method and scope for the preparation of diaryliodonium salts from iodosobenzoic acid-triflate (IBA-OTf) and (3-acetoxyphenyl)-3-iodanediyl diacetate compounds. These compounds could be used in oxidation reactions, replacing commonly used transition metals and would be safer and more environmentally friendly reagents. The preparing of these diaryliodonium salts can be optimized since there are various possible synthesis conditions available. It was important to find optimal methods for preparing diaryliodonium salts, while avoiding the use of toxic transition metals. In the production of pseudocyclic diaryliodonium triflate salts, an acid activated pseudocyclic hypervalent iodine reagent, 2-[hydroxy(trifluoromethanesufonyloxy)]- iodobenzoic acid, can react easily with various arenes in the presence of trifluoromethanesulfonic acid. The synthesis of the pseudocyclic diaryliodonium triflate salts occurs under mild conditions to obtain the iodonium salts in moderate to good yields. Cyclic iodine (III) compounds, arylbenziodoxolones, can be produced in moderate to good yield by reacting pseudocyclic products that are formed under basic conditions. Pseudocyclic and cyclic trivalent iodonium salts can undergo synthesis, with hydroxy and carboxylic acid group compounds, producing these groups in the products and increasing reactivity in compounds obtained. Some of the pseudocyclic and cyclic diaryliodonium salts obtained have been confirmed with single crystal X-ray crystallography. These positive results lead to further investigation of taking advantage of protecting groups and phenyl boronic acid in the preparation of phenolic iodonium triflate salts. Several desired phenolic iodonium triflate salts were obtained in moderate to good yield and are reported as well.