N-Bromosuccinimide CAS 128-08-5 NBS

N-Bromosuccinimide (NBS) is a mild bromination reagent, which is suitable for the bromination of allylic and benzylic positions. It not only has mild reaction conditions, convenient operation, but also has high reaction selectivity. Less response.

NBS can undergo benzene ring bromination reaction with aromatic ethers (such as anisole, m-anisole, α-naphthyl methyl ether, etc.). With a small amount of Friedel-Crafts reaction catalyst, such as aluminum trichloride, zinc chloride or iron, etc., benzene and toluene can also undergo benzene ring bromination reaction with NBS to obtain bromobenzene and p-bromotoluene, respectively.

The addition of N-bromosuccinimide to alkenes under acid catalysis is an important method for the preparation of β-halohydrin. The method has high stereoselectivity, high yield, pure product, mild reaction and convenient operation. The yield reached 82%. The reaction formula is as follows:

Dimethyl sulfoxide (DMSO) is a very effective solvent. Using NBS to react with alkenes in aqueous DMSO, a good and highly stereoselective addition product can be obtained with a yield of 92%. The reaction formula is:

NBS is a very good carbonyl α-bromination reagent, the reaction is easy to operate and widely used. In order to improve the rate and yield of the reaction, many corresponding catalytic systems have been developed. Rapid bromination of 1,3-dicarbonyl compounds by NBS catalyzed by Mg(ClO4)2. The reaction was carried out mildly in CH3CN or EtOAc. The reaction has good stereoselectivity, and can easily prepare α-bromo 1,3-dicarbonyl compounds which are very important in organic synthesis.

The traditional use of N-bromosuccinimide reagents in organic reactions is the bromination of allylic, benzylic, and carbonyl α-hydrogens. With the deepening of research, it is gradually found that NBS can also have many applications in many aspects such as catalyst and oxidant.

• NBS as a catalyst NBS is used as a catalyst, and toluenesulfonamide and alcohols are used as nucleophiles to react activated styrene under mild conditions to obtain the amino groups (yields60%～83%) and alkoxy groups of activated styrene, respectively. Derivatives (yields75%～85%). Both types of reactions are in high yields and 100% use Markov addition. Using NBS as a catalyst, the alcohol was acetylated with acetic anhydride, and the reaction was carried out with chloroform as a solvent at room temperature with high yield and few by-products.
• NBS as oxidant Many secondary alcohols are oxidized to ketones with NBS. The reaction uses a cobalt complex of acetylacetone as a catalyst.
• Application of NBS in polymer research Living polymerization is a very important method to prepare polymers with specific structure and narrow molecular weight distribution. Because the N-Br bond in NBS is very active, it is easy to be broken under heating to obtain active succinimide free radicals and bromine free radicals inert to free radical initiation. Therefore, it is also possible to use NBS as a chain-initiated transfer terminator for free-radical polymerization.