## 3 Oxylabogenation of Hydrocarbons
### Alkenes as Substrates
Regardless of the electronic properties of the substrate, the bromohydrin analogue was consistently observed in significant amounts. [PERSON] and co-workers designed a NXS oxyhalogenation of olefins in DMSO, which employed 2-iodoxybenzoic acid (IBX) as the oxidant [143]. More recent work involved the in situ generation of an IBX derivative via Oxone(r) [(144)]. This versatile method generated a set of _pana_- and _ortho_-substituted \(\alpha\)-bromoketones in good to excellent yields (79-94%). Electron-withdrawing and -donating groups on the substrates were well tolerated by the NBS and Oxone(r) system. Meanwhile, [PERSON] and co-workers demonstrated the solvent-free oxyhalogenation of a variety of alkenes using a NXS (1.1 equiv.) and IBX (2 equiv.) system [145]. The procedure generated 2-bromo- and 2-iodo-1-phenyl-ethanone in, respectively, 86% and 89% yield. The authors claimed that the obtained ketones did not require chromatographic purification, facilitating product isolation significantly. They further stated that the oxidant could be recycled via its waste product 2-iodosobenzoic acid. However, product loss was observed and attributed to the high volatility of the halogenated products. [PERSON] and co-workers designed an effective \(N\),\(N\)-dibromo-\(p\)-toluenesulfonamide (TsNBr\({}_{2}\))-mediated transformation of alkenes into their corresponding \(\alpha\)-bromoketones [146]. Both electron-poor and -rich styrene derivatives were efficiently converted when adding TsNBr\({}_{2}\) (2.2 equiv.) to the starting material in an acetone/H\({}_{2}\)O mixture at room temperature. The resulting products were isolated in good to excellent yields (80-87%). This route stood \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Reaction Conditions** & \(\alpha\)**-Bromoketone (\%)** & **Bromohydrin (\%)** & **Ref.** \\ \hline HBr (2 equiv.), H\({}_{2}\)O\({}_{2}\) (1 equiv.), H\({}_{2}\)O, r.t. & 12 & 53 & [141] \\ NBS (2 equiv.), H\({}_{2}\)O, r.t. & 19 & 81 & [141] \\
30\% aq. HBr (1.7 equiv.), H\({}_{2}\)O\({}_{2}\) & 94 & 4 & [140] \\ (3 equiv.), H\({}_{2}\)O, r.t. & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Aqueous H\({}_{2}\)O\({}_{2}\)-based oxyhalogenation methods. out due to its mild reaction conditions and good efficiency, although it should be noted that TsNBr\({}_{2}\) is not readily accessed [147; 148]. In 2017, [PERSON] et al. reported a CIO\({}_{2}\)-mediated oxidative chlorination of styrene [149]. This route displayed poor selectivity issues as next to the desired \(\alpha\)-chloroketone, five side-products were obtained, significantly complicating the product isolation process (Scheme 56). Furthermore, chlorine dioxide is an extremely toxic and dangerous reagent; its use thus requires strict safety precautions. [PERSON] and co-workers designed an electrochemical Mn-catalysed oxychlorination procedure, using a reticulated vitreous carbon (RVC)-based anode and cathode (Scheme 57) [150]. Fourteen electron-poor and -rich \(\alpha\)-chloroketones were isolated in low to excellent yields. The developed route was not compatible with sterically hindered substrates, as the _ortho_-substituted product was obtained in only 37% yield. As the FeBr\({}_{3}\)-based protocol, the role of a peroxide intermediate was noted. [PERSON] and co-workers developed an aerobic photo-oxidative protocol yielding \(\alpha\)-haloketones from their styrene derivatives [151]. The reaction conditions and scope are depicted in Table 3.  
In 2007, [PERSON] described the synthesis of \(\alpha\)-iodoketones upon irradiation with a fluorescent lamp of a mixture of I\({}_{2}\) (1 equiv. ), O\({}_{2}\) and FSM-16 (mesoporous silica) in EtOAc; with FSM-16 acting as a heterogeneous catalyst (Scheme 58) [152]. Several \(\alpha\)-iodoketones were obtained from their styrene derivatives in moderate to good yields (38-77%). The experimental data showed that the system coped well with the presence of electron-withdrawing (e.g., CI, NO\({}_{2}\)) and -donating (e.g., Me, \(t\)-Bu) substituents on the aromatic ring.