Synthesis and Applications of Cross-linked Poly(N-bromomaleimide) in Oxidation of Various Organic Compounds

Aheterogenous polymeric form of N-bromosuccinimide as an efficient polymeric N-halo reagent for oxidation of various types of organic compounds is introduced. Thus, cross-linked polymaleimides with different cross-linking densities were prepared from maleimide and divinylbenzene using benzoyl peroxide as an initiator by free radical polymerization reactions. The resulting cross-linked polymaleimide resin containing 7% of the cross-linking agent was chosen for further reactions. Cross-linked poly(N-bromomaleimide) (PNBM) was synthesized by the bromination of polymaleimide with bromine/potassium hydroxide, and then characterized. The capacity of PNBM was 6.4 mmol/g measured by gravimetric and iodometric methods. PNBM as a bromine-containing polymer supported reagent was found efficient in the oxidation of alcohols to their corresponding carbonyl compounds, synthesis of ل-ketophosphonates from their ل-hydroxyphosphonates, conversion of oximes to carbonyl compounds, coupling of thiols to their disulphides, and oxidation of sulphides to their sulphoxides. The reactivity of PNBM was found to be much higher than poly(N-bromoacrylamide) or other similar structured polymers. The effect of various reaction conditions such as the temperature, organic solvent, and molar concentration of the reagent on the efficiency of the reactions were examined in order to find the optimum conditions for oxidation reactions. In addition, the efficiency of PNBM was examined in water as a green solvent for oxidation of alcohols to their corresponding carbonyl compounds. The spent polymeric reagent could be regenerated and reused for many times without appreciable loss in its efficiency. PNBM reagent offers several advantages including, high efficiency in oxidation reactions, long shelf life, elimination of hazards related to bromine containing compounds, and regeneration.