## 4 Oxidative Halogenation of Secondary Alcohols  
Closely related to the typical oxhylogenation route, this method relies on the prerequisite setup of a secondary alcohol group and offers straightforward access to \(\alpha\)-haloketones. [PERSON] and co-workers developed a H\({}_{2}\)O\({}_{2}\)/HBr system which converted three secondary benzylic alcohols into their corresponding \(\alpha\)-bromoketones in moderate to good yields (52-85%) (Scheme 63) [162]. The system was not compatible with _ortho_-substituted 1-phenylethanol derivatives, as the reaction yield dropped significantly (52%). The developed method showed outstanding selectivity, as exclusive formation of the \(\alpha\)-haloketone was observed. The authors claimed that the role of the ratio HBr/H\({}_{2}\)O\({}_{2}\) (1.2:10) is crucial to obtain these results. H\({}_{2}\)O\({}_{2}\) is most likely responsible for oxidizing the corresponding alcohol to generate the carbonyl moiety and for oxidizing Br\({}^{-}\) to Br\({}_{2}\) (or HOBr), the active bromination agent.  
The dual role of a urea-choline chloride-based deep eutectic solvent (DES) in the oxidative bromination of secondary alcohols was demonstrated by [PERSON] and co-workers (Scheme 64) [163]. 2-Bromo-1-phenylethanone was obtained in 68% yield when adding three equivalents of NBS to the corresponding alcohol in the DES. Remarkably, the DES both acted as a catalyst system and solvent in this transformation. Recent studies illustrated the superiority of DES in comparison to ILs, linked to their non-toxic nature, easy and low-cost synthesis [164]. Although the mechanism was not fully disclosed, NBS was most likely responsible for both the bromination and oxidation, with DES activating the N-Br bond.  
[PERSON] and co-workers established an aqueous, green and efficient way to generate \(\alpha\)-iodoketones from secondary alcohols via addition of NH\({}_{4}\)I and Oxone(Scheme 65) [165]. The procedure generated a yield of 72% of 2-iodo-1-phenylethanone, but the yield dropped significantly for alcohols bearing substituted aromatic rings (i.e., \(p\)-Me, \(p\)-Br, \(p\)-NO\({}_{2}\), \(m\)-OMe). The developed method proved inefficient for substituted 1-phenylethanol derivatives. In 2017, the authors updated the procedure in order to access \(\alpha\)-bromoketones via their corresponding alcohols upon the addition of NH\({}_{4}\)Br (2 equiv.) and Oxone(r) (3 equiv.) [166]. This altered procedure yielded 10 \(\alpha\)-bromoketones in low to excellent yields (38-94%). Nitro-substituted benzylalcohols appeared to be deactivated in the developed system. Furthermore, undesired ring bromination exclusively occurred for methoxy substituted 1-phenylethanol derivatives. Despite the progress made in terms of sustainability, this route still shows a rather moderate oxyhalogenation efficiency and selectivity.  
In 2014, a method for the oxychlorination of 1-phenyl-ethanol was reported by [PERSON] and co-workers (Scheme 66) [167]. Ten \(\alpha\)-chloroketones were isolated in good to excellent yields (70-87%) by stirring the alcohol substrates with a mixture of trichloroisocyanuric acid (1 equiv.), TEMPO (0.1 equiv.) and MeOH (2 equiv.) in DCM for 5 h. The presence of electron-donating and -withdrawing groups on the substrates was well tolerated. The protocol stands out as it employs a commonly used bleaching and disinfectant agent (i.e., trichloroisocyanuric acid) in a chemical process.