Studies On Novel Methods For Arene Bromination And Alkene Bromohydroxylation

This thesis is simply composed of two parts:The first one is about background introduction of the important applications in medicine, agriculture, and organic syntheses and preparations of aryl bromides and vicinal bromohydrins. Basically there are four synthetic routes to the direct preparation of aromatic bromides. Namely, starting from elemental bromine and various catalysts, from N-bromosuccinimide(NBS), from complexes of bromine and various compounds, and from oxidatively in-situ formed elemental bromine. Meanwhile, there are generally three synthetic routes to the preparation of vicinal bro-moydrins:reduction of substituted α-brominated acetones; ring-opening of epoxides; and direct bromohydroxylation of alkenes.The second is our research on the novel methodologies of the syntheses of aromatic bromides and vicinal bromohydrins, accompanied with corresponding reaction condition optimization, discussion about mechanisms and substrate scope and limitations and finally with the information on products characterization.The general bromination of arenes proceeds under such conditions:potassium bromide as the bromine source; Iodine pentoxide as the oxidant; and distilled water as the reaction medium under ambient temperature. The reaction is tolerant with various compounds such as (even with strong electron-withdrawing groups, for instance, carbonyl group) aryl ethers, anilines, and alkane group substituted aromatic compounds, and some electron-rich heterocycles, with moderate to excellent yields. But bromination doesn’t proceed with such deactivated aromatics as benzonitrile, benzaldehyde, and nitrobenzene.Meanwhile the vicinal bromhydroxylation of olefins undergos in the following condition:potassium bromide as the bromine source; Iodine pentoxide as the oxidant; water/acetonitrile (1:1, v/v) as the mixed solvent at room temperature. The reaction tolerate almost every aromatic olefin except those heterocycles, with yields varied between60%to98%. And the new methodology itself displays a good regioselectivity and stereoselectivity. In another word, the addition position of the hydroxyl group is at the benzyl position and forms trans-isomers.