Bismuth(III) salts mediated regioselective ring opening of epoxides: an easy route to halohydrins and β-hydroxy nitrates

The ring opening of various epoxides was achieved under mild conditions using bismuth(III) salts. Halohydrins and β-hydroxy nitrates were efficiently obtained from the corresponding 5α,6α-, 2α,3α-, and 5β,6β-epoxysteroid using BiCl3, BiBr3 or Bi(NO3)3·5H2O. Considerations about the probable reaction mechanism are provided. 2D homo- and heteronuclear correlation NMR spectroscopic techniques were used to unequivocally demonstrate the trans-diaxial nature of the epoxide ring opening.