A novel and efficient method for the Cr(II)-mediated desulfonylation of α-sulfonyl ketone by a Cr-ligand-Mn system has been developed during the course of process research on Halaven (eribulin mesylate). This reaction is dramatically accelerated in the presence of an appropriate bipyridyl-type ligand. This system is applicable to reduction of α-sulfur-substituted ketones. In addition, a Cr-Cp2ZrCl2-Mn catalytic system is also applicable to desulfonylation of α-sulfonyl ketone.