l,3-Dibromo-5,5-dimethylhydantoin

(A) Auerbach et al. reported a useful method for bromination of activated benzoic acids using the DBDMH in aqueous NaOH. They reported high yields (90-98%) and purity (99.9%) for bromides of several benzoic acids. It was also shown that DBDMH gave better yield that NBS. (B) Chassaing et al. reported the enhanced reactivity of DBDMH in the presence of trimethylsilyl trifluoromethanesulfonate. They obtained very good yield of monobromide in the presence of TMSOTf. whereas without TMSOTf, either a mixture of bromides or starting material was recovered. (C) Similarly, Eguchi et al." used DBDMH in the presence of organic and inorganic acids of pKa values less than -2 to get the monobromide in excellent yields. It gave very good yields even for aromatics having electron-withdrawing substituents. For some cases, a catalytic amount of acid was sufficient. (D) Recently, we investigated the bromination of a wide variety of phenols and polyphenols using DBDMH. The aim was to prepare pure ortho- monobromophenols of different methyl gallates. A simple treatment of various methyl gallates with 0.5-0.55 equivalents of DBDMH resulted in the desired ortho-monobromides in very good to excellent yield and purity. Interestingly, we prepared both regioselective bromide units in very high yields for the synthesis of a- and (beta)-DDB. (E) We also studied^ the regioselective bromination of pyrogallol derivatives by DBDMH. which gave regioselective single monobromides in 77% yield in 90 minutes at room temperature. (F) Very recently, we found that DBDMH is an excellent oxidizing agent for the oxidation of different thiols to their corresponding disulfides in extremely high yield and in very short reaction time. It was found to be superior to other oxidants, the reaction was very clean, and no other oxidized side-products were found.