Hydrogen Bromide → 1-Bromomethylthio-4-chlorobenzene

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Reaction Steps

To a slurry of paraformaldehyde (36.24 g, 1.21 mol, 1.58 equiv) in toluene (243 ml) at 22° is added aqueous hydrobromic acid (48.5 wt %, 652 ml, 5.86 mol, 7.68 equiv) with an endotherm to 18°. The resultant biphasic solution is warmed to 40° and a solution of 4-chlorothiophenol (VII, 138.81 g, 0.960 mol, 1.26 equiv) in toluene (116 ml) is added over ½ hour while maintaining 40-43° and rinsed in with toluene (50 ml). The mixture is then warmed to 50° and stirred 1 hour. The mixture is cooled to 10°, the phases separated, and the aqueous washed with toluene (250 ml). The combined organics are treated with ice water (500 ml), hexanes (350 ml) and the phases separated. The aqueous phase is then washed with toluene (200 ml) and the combined organic phases are dried over magnesium sulfate and concentrated to give crude bromomethylthio-4-chlorobenzene (268.01 g), NMR 7.43, 7.34, 4.79 δ; CMR 134.37, 132.05, 131.78, 129.46, 37.32 δ; HRMS (EI+) calculated for C7H6BrClS=235.9063, found =235.9063.

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