Equilibrium shift induced by chiral nanoparticle precipitation in rhodium-catalyzed disulfide exchange reaction

Chiral silica (P)-nanoparticles grafted with (P)-helicene recognize the molecular structure of a chiral diol disulfide in the presence of monool disulfide and dibutyl disulfide. The (P)-nanoparticles selectively adsorb the diol disulfide, aggregate, and precipitate from solution. Under rhodium-catalyzed equilibrium among three disulfides, the diol disulfide is removed from solution by precipitation, which induces an equilibrium shift in the solution. By conducting the precipitation experiment twice, we obtained the diol disulfide in 37% yield from a statistical 1:2:1 equilibrium mixture of three disulfides. The method is applied to a racemic monool disulfide, and an optically active diol disulfide is obtained via kinetic resolution and equilibrium shift.