## 6 Hydration of 1-Haloalkynes
### Metal-Catalysed Hydrations  
Similarly to the hydration of alkynes [187; 188], gold complexes have exhibited an excellent catalytic activity in the hydration of 1-haloalkynes [189]. [PERSON] and co-workers described the hydration of 1-haloalkynes catalysed by a gold catalyst immobilised on mesoporous MCM-41 resin [190]. The versatility of this heterogeneous catalytic route was demonstrated by its broad substrate scope. Sixteen \(\alpha\)-bromo, four \(\alpha\)-chloro and four \(\alpha\)-iodoketones were obtained in excellent yields (Scheme 72). The authors claimed that the catalyst can be recycled and reused for eight consecutive runs without significant loss of catalytic activity. Additionally, they stated that after these eight runs, gold leaching did not occur. The excellent atom economy, mild reaction conditions, the generality and catalyst recyclability elevated the importance of this protocol compared to the state-of-the-art. In 2019, the same group reported an updated procedure relying on the in situ activation of MCM-41-[Au(Cl)(PPh\({}_{3}\))] (2 mol%) by AgNTT\({}_{2}\)[191]. Despite the decreased catalyst loading, this route's scope was very limited, as only 2-bromo-1-phenyl-ethanone (92%) was obtained. Another gold-catalysed protocol using [Au(NTT\({}_{2}\))(XPhos)] to perform the hydration of 1-bromo and 1-chloroalkynes was designed by [PERSON] and [PERSON] [192]. Ten aromatic \(\alpha\)-bromoketones and two aromatic \(\alpha\)-chloroketones were isolated in low to excellent yields (up to 97% and 91%, respectively), upon of addition of 3 mol% of the catalyst and water (3 equiv.) to the 1-haloalkyne in dichloroethane. The presence of electron-donating (i.e., Me, \(t\)-Bu, OMe) and -withdrawing (i.e., F, Br) groups on the substrates was well tolerated. However, the hydration efficacy of the system decreased significantly for sterically hindered substrates. The hydration of the _ortho_-substituted 1-haloalkynes yielded the corresponding ketones in trace amounts. Furthermore, the protocol demonstrated a substrate specific nature, as it did not accommodate the hydration of 1-iodoalkynes. More recently, [PERSON] and co-workers developed an efficient catalytic protocol for the Au(I)-catalysed hydration of 1-iodoalkynes (Scheme 73) [193]. The use of Au(I)-NHC catalysts enabled the straightforward synthesis of several aromatic \(\alpha\)-iodomethyl ketones in good to excellent yields. The utility of this simple method was further highlighted by showcasing iodination/hydration and hydration/oxidation sequential protocols leading to the construction of molecular complexity. A broad scope of \(\alpha\)-haloketones was also obtained via the Cu(OAc)\({}_{2}\cdot\)H\({}_{2}\)O and trifluoroacetic acid (TFA) promoted hydration system developed by [PERSON] (Table 7) [194]. This route coped well with substrates bearing electron-withdrawing and -donating groups. The authors claimed that the catalyst can be recycled and reused for five consecutive runs without loss in hydration activity. In 2014, [PERSON] and co-workers reported the remarkable catalytic activity of the AgF/TFA system in the hydration of alkynes (Table 7) [195]. This system tolerated a wide variety of functional groups attached to the phenyl ring (i.e., CF\({}_{3}\), Br, Me, NO\({}_{2}\), OMe, etc.). The procedure showed a substrate specific character as it did not mediate the hydration of 1-iodoalkynes. The use of the strongly acidic TFA is a major drawback, and negatively impacts the functional group tolerance of both routes.