1- Hexene reaction with hydrogen bromide

On the other hand, when 39 was heated with hydrogen bromide in acetic acid, 1,2-di-<9-acetyl-( 1,3/2,6)-3,4-dibromo-6-(bromomethyl)-l,2-cyclohexanediol (50) was obtained, which was converted into 1,2-di-0-acetyl-( 1,3/2)-3(bromomethyl)-5-cyclo-hexene-l,2-diol (51) by debromination with zinc dust in glacial acetic acid [21]. Hydro-xylation of 51 with osmium tetroxide, and successive acetylation yielded 1,2,3,4-tetra-C>-acetyl-6-bromo-6-deoxy-pseudo-a-DL-glucopyranose (52). Nucleophilic substitution reactions of 52 with sodium acetate gave pseudo-a-DL-glucopyranose pentaacetate (55), which gave pseudo-a-DL-glucopyranose (54) by usual hydrolysis [22]. Alternatively, the pentaacetate 55 was obtained as a minor component in a poor yield by nucleophilic substitutions of 2,3,4-tri-0-acetyl-l,6-dibromo-l,6-dideoxy-pseudo-... 

The oxidative bromination of Cs-Cg olefins can be carried out using a system composed of catalytic thallium(iii) oxide (0.2 M of Tl(iii)) and a vanadium-based heteropolyacid cocatalyst (HPA-n = H3+ PMOi2 V 04o n = 2-8) in the presence of hydrogen bromide solution (1.0 M of Br ) and oxygen as co-oxidant. The HPA-n cocatalyst can promote oxidation of thal-lium(i) to thallium(iii) in the presence of bromide ions. For instance, the reaction of 1-hexene with the thallium(iii)/HPA-6/bromide system at 100 °C and 8 bar of oxygen led to a mixture of 1,2-dibromohexane and hex-enebromohydrin along with a small amount of 2-hexanone in different ratios. In the absence of thallium(m) species, the oxidation process proceeds slowly, presumably due to the HPA-6 anion-mediated oxidation of bromide to bromine. 

The results for the cyclization of the l,l,5-trimethyl-5-hexen-l-yl radical, formed from the reaction of l,l,5-trimethyl-5-hexenyl-l-bromide (3) with Bu3SnH/AIBN, are shown in eq. 3.2. These results indicate that the ratio of 5-exo-trig marmer/6-endo-trig manner depends on both the temperature and concentration of Bu3SnH. Thus, as the concentration of Bu3SnH at 40 °C is decreased (which means the decrease of the concentration of the hydrogen donor), both a decrease of the direct reduction product,... 

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