Thiol acids reaction with halo ketones

Thiols efficiently dehalogenate a-halo and a,a-dihalo ketones. Reduction is typically carried out in ethanol containing a weak base. Although this system will also reduce a-thio ketones, it is believed that the halo ketone is reduced, and that reaction proceeds as in equation (11), with a proton from the solvent serving as Lewis acid to assist dehalogenation by thiol (or thiolate). The reactions are of course accelerated by inclusion of a metal salt in the medium. ... 

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