Asymmetric Synthesis and Configurational Stability of C2-Symmetric Hexacoordinated Phosphate Anions (TARPHATs) with Predetermined Chirality from Tartrate Esters

Abstract

C2-Symmetric TARPHAT anions 5 made of a central PV atom, one tartrato (=dialkyl 2,3-di(hydroxy-κO)butanedioato(2−)), and two tetrachloropyrocatecholato (=3,4,5,6-tetrachlorobenzene-1,2-diolato(2−)-κO,κO′) ligands can be easily prepared in decent to high yields (50–86%) as their dimethylammonium salt by using a one-pot process and simple commercially available starting materials. The presence of the chiral tartrato ligands (usually (2R,3R)) leads to the formation of diastereoisomeric anions ((Δ,2R,3R)/(Λ,2R,3R)). Decent to good control by the chiral ligands – under equilibration conditions – over the Λ or Δ configuration of the adducts was observed (d.r. 84 : 16 in CHCl3 for the di(tert-butyl) tartrate derivative), the selectivity depending on the nature of the ester chains as well as on the solvent.