On the diastereoselectivity of cyanide addition to β-hydroxyketones: One-pot synthesis of syn β-hydroxycyanohydrins and anti 2,4-dihydroxyamides

Article abstract of DOI:10.1016/S0040-4020(01)85299-6

The intrinsic stereoselectivity of the cyanide addition to β-hydroxyketones in the presence of 18-crown-6 or ZnI₂ is lower than that previously reported. However, the reaction bears a practical value in that syn β-hydroxycyanohydrins and anti 2,4-dihydroxyamides can be diastereoselectively obtained in reasonable yields in a one-pot procedure. The high d.e.'s initially reported were due to the work-up procedure, where the HCl converted much faster the anti β-hydroxycyanohydrin than the syn product into the corresponding amide. This faster conversion is explained in terms of antichimeric assistance of β-hydroxyl group. Details are given as to the configurational assignment of products by 2D NMR and molecular mechanisms.